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Ht ; oH mA Ms iq 7 ; Laan ey t . f ate ; sie , Ly Aaigeeheranaclastaaa UE Ma ieee ae conememaneaena Feacng eee: ATS By ei PME AE a Vi Mia? i eats ihe te on a nie Roe jae Pp Wess iae ” i vie hi bl pty pet: “ vie ast tahel os De eta rte bee ain bo ulin ayvaebeatie tne! ; Rey 4 : pee eb yeaney aah sacs i oartaee aie NayEas eA) WV eg Po ae sae yi rissa ves a in = oto : Ban % H i ri } rs wah : St svitg ! 7 b ie As peat oy i ook 1 Heaths eH arwtanteas Ot fa THE UNIVERSITY [2 Cee OF ILLINOIS | | ree ul val eerie te cas a he aoe RY Uae fine KEVATIONZOF PLANTS TO SLD BEV ES A STUDY OF FACTORS AFFECTING THE DISTRIBUTION OF MARINE PLANTS BY DUNCAN S. JOHNSON AND HARLAN H. YORK WASHINGTON, D. C. PUBLISHED BY THE CARNEGIE INSTITUTION OF WASHINGTON 1915 CARNEGIE INSTITUTION OF WASHINGTON PUBLICATION No. 206 Copies of this Gor were first issued DEC 311915 The Lord Baltimore Press BALTIMORE, MD., U. 8. A. x I. II. III. IV. ‘a XN + ¥, ‘a Maes VIL. > VIII. are IM NW. CONTENTS. Initiation of the Work; Its Purpose; Acknowledgments................ Location and Physical Features of the Area Studied; Mode of Deter- mining and Mapping the Distribution of Plants, Physiog- EN IUCR Ua ek LS cain Fah anne VS os RAG aso dla Wid Bean dw © ahs 1. Location, Construction of Map, Mode of Discovering and Recording thie: Postlionss of4 Planter: 4 4.6r oir. Cee ee ces ecees 2. Topography of Harbor; Size, Depth, Character of Bottom and Shores. 3. Tide-levels; Mode of Determining Height and Rate of Rise and Fall CE OS ee ee eM ee eee re hes Cee Re ae CL Ee RS ate mae tree eae Plant Associations; Characterization of the Belts or Zones of Vegeta- tioneana. Their. DIStripntion. 0. co. cee st he eee ec ey wee ease LON A: PUREST LUBE CLL rere cee le GME Snares MONS eae ere ete ere eo ee oe ee sc sée ea 2. The Bottom Vegetation of the Harbor from —5 to +41.5 feet (the Sub Littoral and Lower Littoral Belts).................. A. Plants of Loose Soil (The “ Enhalid Formation ” of Warming).. B. Attached Alge of Harbor Bottom: ‘“ Lithophilous Benthos’”’.... COEpiphytic Atere on Sostora-and) Ulver. Pe. Clee. Oe cw icees "The Midtittoralshelt tron £6 to 0 Teer. Fe Sr eS SO oe ca ae Ai Tite MiG-Hiiioral Marsico ee ee ete oe eh ce wakee bases ene Per RiuGtSPArlLind Petal AOSOCIALIOM Sie ce kek wa ee d's a See eae kas oo bie Ale OL the MiIG-ttOral Marah ss oo... oe ues ww coe ow B. The Mid-littoral Rockweed Association, on Wharves........... Poet i OCE LaALLLOreti. Get, 1 TONG. LO. LOCK 6 oo. ac aa5 pices 6 accsoisile ) wave 2 ol A. Seed Plants of the Upper Littoral Belt (Associations of Spar- tina patens, Sueda, Salicornia, Juncus, or Scirpus)....... Pee ae OF Le CCE LLLOLAT TIGA, fat tins gs a cutaeus t svlekre age ath « vs se « ee ire tee COPaL Et CATO G00 he COOL oc ccte scan « 5 cas steuuheeo Le cuake widiain A. The Supra-littoral Beach or Storm Beach.................... 1. Storm Beach of the Spit (from 8 to 12 feet)............... 2. The Supra-littoral Beach, or Storm Beach, of East and West Sides of the Harbor (from 8 to 10 feet).................. B. Supra-littoral Belt of the Marsh, or Brackish Marsh (8 to 10 ft.). 6. Description and Map of Belt Transect of the Marsh (1.5 to 10 ft.).... Factors Influencing the Distribution of Littoral Plants................ ss EE Pe eee ee aa a Ree etre ene as on eae eee ane, sean A. Living Substrata (Plante or Animals) oc... ce he ee we hes Peep OT Divi iret at cee ee ee ue deus ee tsees a tie ces fo Lite oo ens tie 1. Soils as Substrata (Gravel, Sand, Mud, Humus, or Peat).... 2. Solid Substrata (Stones, Pebbles, Shells, Piles, and Logs)... Zn (HNMEUCE OL TW ALEr-CUlTeCn tints ce ate ae ee ee eee each eee 3. Character of Tidal Changes and their Influence on Plant Distribution. Uonracter and Mabnitugae OF, LNG. T1GCH oc 2c i. esc ce 2 esse cette. . Effect of Tidal Changes in Water-level on Evaporation or Trans- Piva ciOl LEO. CUS Piatti ys ay a cae 400 West, showing Ulva covering Bottom, and Tide Channels from Creek. B. Looking over Harbor Bottom from 100 North * 40 West to 600 North x 1,000 East, showing Ulva on Bottom and Tide Channels from Tide Pond; at Right Middle Ground the Northernmost Tongue of Spartina glabra alterni- flora from Marsh. LAING! “Thy or? bm as FS ‘ arr 7 a i PLANT ASSOCIATIONS ahy) higher belt, where these associations have a somewhat different make-up. On stony substrata within the limits of this belt, which are confined practically to the walls of the wharves, we find a nearly continuous rockweed association. This is dominated by Fucus vesiculosus, F’. evanescens, and Ascophyllum nodosum, but it embraces also a considerable number of smaller alge of all classes, many of them very numerous. A few of the latter are found on the fringing marsh also, but most of them are not. (4) The upper littoral belt extends from 6.5 feet to 8 feet. On gravelly, well-drained portions of the shore this level is usually dominated by Salicornia or Sueda, and less frequently by Spartina patens, often mixed with Distichls. These are the areas that we have called “upper littoral beach.” On flat, poorly-drained shore with peat-like soil we find an upper littoral marsh dominated by Spartina patens, by Distichlis spicata, or by Juncus Gerardi. Where the soil is more or less saturated with fresh water Scirpus americanus dominates. This apparently corresponds in most respects to the “ salt- meadow ” of Warming. (5) The supra-littoral belt of vegetation extends from high-water level at 8 feet upward as far as the direct influence of the sea is felt by the vegetation, which is often 10 feet and on the Spit up to 12 feet. In this belt also we find two distinct associations, determined by the character of the soil, especially by its drainage. In sandy, well-drained portions, which are found only on the Spit, we find a supra-littoral beach, or storm beach, dominated by Ammophila arenaria, with which are associated three or four prominent species of dico- tyledons and a score of other species, chiefly seed plants, of less frequent occurrence. On flat, undrained portions of the shore between these levels, where the peaty soil is subjected to submergence by spring tides, and is in many places kept continually moist by subterranean fresh water, we have a supra-littoral marsh, the “ higher littoral marsh” of Warming. This sort of marsh is well- developed only at the head of the harbor. Near the 8-foot level the soil-water is brackish or nearly salt, while near the upper limit of this marsh at the 9-foot level the soil-water is practically fresh, at least during the growing-season. In consequence, evidently, of this difference in salinity, and in other soil characters, as well as in elevation, the vegetation differs greatly in different parts of the marsh. The lower, more saline portions are dominated by Spartina patens or by Juncus Gerards, while fresher areas are characterized by Scirpus americanus, and the highest parts are occupied chiefly by Aspidium thelypteris. 1. THE PLANKTON. The plant constituents of the plankton of the Inner Harbor consist of a relatively few species of diatoms of the genera Melosira and Navicula, and a few species of Peridinaces. Of the latter one species of Glenodinium often occurs in such numbers, over areas of scores of square meters, and to a depth of 0.5 meter or more, as to color the water a deep brown. This condition was frequently noted two or three times a summer, and often lasted for several successive days. Professor C. B. Davenport informs us that this or a similar species of the Peridines is sometimes so abundant in September as to kill many of the fish in the harbor by clogging their gills. The time at our disposal did not suffice for a detailed study of the plankton and its daily and seasonal variation. 2 18 THE RELATION OF PLANTS TO TIDE-LEVELS 2. THE BOTTOM VEGETATION OF THE HARBOR FROM -5 TO +1.5 FEET (THE SUB LITTORAL AND LOWER LITTORAL BELTS). The present belt includes 1.5 feet of the lower part of what Kjellman calls the “ littoral region,” 1. e., of the strip between low and high tide marks. It also includes 5 feet vertically of bottom below the mean low-water level, 4. ¢., 5 feet of what Lorenz calls the “ submerged littoral region.” The plants forming the bottom vegetation of this harbor consist of (A) plants of the loose soil; (B) algz attached to stones or shells; (C) epiphytes living chiefly on members of group A. A. PLANTS ON LOOSE SOIL (THE ENHALID FORMATION OF WARMING). This formation includes two seed plants, Zostera and Ruppia, which are rooted in the soft bottom, and only two important alge, Ulva lactuca and Enteromorpha clathrata. Most of these latter are unattached, and either simply rest on the bottom or are weighted down by mud or mussels. The Ulva grows in sheets, the Hnteromorpha in tangles. In looking down on the bottom of the harbor from the neighboring hills at low tide, 1. e., with the water- surface at —1 foot, the bottom over most of its area appears green in color. This green color is due to the presence of the more or less uniform covering either of Ulva lactuca or of Zostera marina, or, on some smaller areas, of Enteromorpha clathrata. The most considerable bare area on the part of the bottom, exposed by the lowest tides, is that at the north and northwest portions of the harbor, which lies between the —1-foot level and the 2-foot level. Besides this there are two or three narrow strips, 12 to 15 feet wide, and trending more or less northward from the mouth of the main fresh-water stream at 200 north by 550 east, which are rather constantly bare. (See plates 11 and vit.) There are other smaller changeable bare spots on various parts of we bottom outside the Zostera belt. Of those portions of the harbor bottom still covered a the water is at —1 foot, the bottom of the tide-channel starting near the wharf of the Research Laboratory at 1,100 north by 400 west, and emptying into the deep hole at 1,400 north by 400 east, is nearly bare of Ulva and Zostera. Likewise, the greater por- tion of the deep hole itself, and of the channel leading from it to the Outer Harbor, have a rather bare, sandy, shelly, or pebbly bottom, except for that portion to the east and south of the deep spot which is indicated on the map as covered with Zostera. The plants of Ulva found under these more swiftly moving waters are small attached plants which are evidently being carried along with their supports. ‘The area occupied by a dense growth of Zostera is indi- cated on the map by a wavy outline marked Z. Its distribution will later be described in some detail. The rest of the harbor bottom below the 1.5-foot level, aside from the bare areas mentioned above, is rather completely covered with Ulva. This Ulva occurs in the form of innumerable detached flattish, or crumpled, or bullate and often perforate and ragged sheets, of all sizes from a few decimeters to 10 meters across. The distribution of much of this Ulva over the bottom is more or less inconstant. Often the bottom is covered completely for hundreds of square meters, e. g., 400 to 1,000 north by 200 west to 400 east. In other portions of the harbor only one-half or three-fourths of the bottom is actually hidden by the Ulva, e. g., near the west side at 0 to 600 north, or near 200 north by 400 west. ENHALID FORMATION 19 On closer examination of the Ulva plants of the harbor, it is found that practically the only attached plants present are relatively small, being 1 to 5 or 6 dm. across. These are found chiefly on pebbles and shells along the sides of the channel of the Inlet leading to the Outer Harbor and beside the main fresh-water streams, e. g., at 200 north by 550 east, at 200 north by 950 east, at 2,380 north by 980 west. A few attached plants were found on stakes, on buoys, and on shells of living mussels in various parts of the harbor. A very few attached plants occur on the rhizomes of Spartina glabra and on stones of the wharves in the next higher belt. The widespread, though sparse, dis- tribution of these plants in the harbor probably indicates that zoospores are abundant there. The practical absence of attached plants from most parts of the harbor bottom is evidently due to the lack of proper substrata, except where entering streams or tidal currents leave a surface of coarse particles on the bottom. ‘The detached sheets of Ulva covering the bottom may become second- arily fixed by the attachment to them of numerous mussels or of snails. In other cases parts of the sheet of Ulva may be buried, and thus fixed, by the mud shifted by water-currents or by burrowing animals. The general distribution of Ulva described above is that found each summer, in July and August, for six years past. The exact size and position of the minor bare spots in the Ulva zone changes from year to year, and in fact from week to week or even from day to day, due to the movement of the free Ulva by water-currents. In December 1912 the Ulva was about as abundant in the harbor as in summer. The bottom of the harbor was reported as nearly bare of Ulva in February 1913. In the following April, however, Dr. A. F. Blakeslee found many small sheets on the mud at the south end of the harbor. A somewhat detailed examination of the harbor in April 1911 showed that the bottom above mean low water is much less completely covered with detached Ulva than in midsummer. In fact, large sheets were almost wanting in those parts of the harbor that could be examined. On the other hand, a search for attached Ulva, in the places where it occurs in summer, showed that it was far more abundant in April. On the east side of the channel to the Outer Harbor, for example, there were thousands of attached plants of Ulva, of all sizes up to 1.5 or rarely 2 dm. across, and all of them were evidently growing vigorously. In July 1911 these same areas bore a much smaller number of plants, of which the largest in the middle of the channel were about 6 or 8 dm. long. In the inrushing tide near the Inlet one may always find plants of Ulva or parts of plants floating in with the current, and thus being carried to the quiet parts of the Inner Harbor, many of them settling on the bottom with the next fall of the tide. These floating sheets are evidently plants that have been broken off from their supports or substrata in the Inlet and elsewhere where young plants are developed abundantly. The maximum size of fixed plants found in the Inlet in July 1911 (about 6 dm.), is probably the size at which the tensile strength of the base of the plant is just able to withstand the strain of the swiftest tidal currents. Plants larger than this are torn off, or carried away with their supports, as even smaller ones also may be, and are thus added to the covering of the bottom of the Inner Harbor. It seems clear from the facts just mentioned that the large, free sheets of Ulva in the Inner Harbor are developed by the continued growth and crump- ling of the relatively small and flat plants that have been torn from their 20 THE RELATION OF PLANTS TO TIDE-LEVELS original attachment in the Inlet and on other pebbly bottoms of the harbor. Such detached plants of Ulva do not necessarily lodge within the Ulva zone the first time that they are washed into the harbor; neither do they stay indefinitely at the point where they first lodge. Even larger sheets that have been resting on the bottom for days or weeks may be moved about by the water in one of two ways. In the first place, sheets that lie on the flats bordering the tide-channels may be rolled up by the tidal current of large, swiftly flowing spring tides, and gather additional sheets as they are tumbled along over the flats, until rolls are formed 0.5 meter in diameter and 2 or 3 meters long. These rolls have been seen to roll for 40 or 50 meters over the shoals near 2,000 north by 200 to 800 east. Such rolls may evidently either be carried out to the Outer Harbor, or be broken up again, with considerable tearing of the sheets, and the fragments floated back to be redistributed over the bottom of the harbor. The long bare strips of bottom noted above are often merely the trails of such rolls. The second mode of transportation is one that is seen on days that are bright and windy, during extreme low water, especially of spring tides. ‘The long exposure of the Ulva-covered parts of the bottom at such times allows the water to drain off and permits air, and probably other gases from the underlying mud, to collect under the coarsely crumpled sheets. With the rising of the tide these sheets or portions of sheets of Ulva are floated up 2 or 3 feet off the bottom or even to the surface at high water, and finally, becoming entirely free from the bottom, they are blown by the wind along the surface of the water. Such floating plants may drift about the harbor and then out through the Inlet with the next fall of the tide, or they may settle in new places on the bottom, or with stronger winds they are sometimes blown to the shore, where they may become tangled among the reed grass or drifted on the beach. Windrows of Ulva thus formed are often found on the beaches between the 3 and 8 foot levels, or caught in the Spartina glabra, sometimes covering many square meters. There the plants finally die from exposure to the sun and rain. Just what part this floating of the Ulva may play in finally denuding the bottom of the harbor was not determined by an actual counting of the floating sheets and a measurement of their sizes, but it is evident that it may be a very considerable one. It is, however, probably small in comparison with the destruction and transportation of Ulva accomplished by the ice, though the importance of this factor is also undetermined, since we have not been able to study the harbor in detail in winter. If the history of the sheets of free Ulva found on the harbor bottom in July is that which has just been suggested, then it is certain that the growth of those plants which settle in favorable places must be very rapid. One of the larger sheets measured in August was found to be 10 meters long and about equally broad. The production of such a plant as this in 3 or 4 months from one 6 or 8 inches across indicates the remarkable average rate of radial growth | at all parts of the margin to be 30 or 40 mm. per day. Assuming that the largest plant seen in July 1911, located just aside from the swiftest current, had come from the largest plants seen in April 1911, the rate of growth would average only 8 or 10 mm. per day. Actual measurements by Miss Stella G. Streeter of the rate of growth of somewhat smaller plants growing under natural conditions in July and August 1910 give a daily incre- ENHALID FORMATION 21 ment much smaller than this. For example, a series of young plants averaging 26 mm. in length increased to an average length of 55 mm. in 20 days. The average daily rate of growth was 1.5 mm. and the maximum daily increment was 2 mm. It is of course possible that the large sheets of Ulva may winter over in some of the deeper, more protected parts of the Inner Harbor, and less probable that they may be washed in from the Outer Harbor. The rates of growth actually observed indicate that the largest of these plants can not be produced from spores in a single season. It is hoped that observations now under way may definitely determine the age of these larger sheets. It is of course possible that the larger amount of sewage present in the water in summer, during the session of the Biological Laboratory, may enable the Ulva to grow more rapidly than in winter or spring. (See Cotton, 1911, and Letts and Richards, 1911.) The lower limit of distribution of attached plants of Ulva in the Inner Harbor is very near the mean low-water level. Plants which are drifting with their supports and torn off bits may be found at greater depths, but we have not determined how long they can persist there, and there is no adequate evidence that zoospores of Ulva develop to young plants at levels more than 6 inches below mean low water. Why this species is confined to levels which are exposed to air and light has not been determined, but apparently it is due to the direct effect of some physical factor, since there are, in most places, no competitors, and there are, at least in some places, suitable substrata for attach- ment some distance below this limit. Since Ulva occurs in the next higher zone, we may discuss the factors determining its upper limit in that connection. Ulva probably influences the distribution of other plants only as it forms the substratum for certain epiphytic diatoms and a few species of blue-green alge, of which latter Spirulina is the only form of any importance. It is probable also that the smooth sheets of Ulva lying on the mud may prevent _ young seedlings and broken off bits of Zostera from getting a hold in the mud. Finally, the floating masses of Ulva, like other flood trash, may smother out many square yards of Spartina patens, or other plants already established on the marshes, by settling on them with the fall of the tide. The bare patches so formed often become re-covered first with Vaucheria or seedling Salicornias, as will be described later. Enteromorpha clathrata: This plant, as we shall find, is not by any means confined within the 1.5-foot contour line, but may be found as high as the 6 or 6.5-foot level. It does, however, occur far more abundantly on the bottom of the harbor than elsewhere. As one rows over the harbor just before low water on a quiet day, he will see on the leaves of Zostera numerous tufts of sparsely branched, crinkled, green, tubular filaments, 1 or 2 mm. in diameter, and com- monly from 5 to 20 cm. in length. These are the young plants of probably a few weeks growth of Hnteromorpha clathrata. Observations made in the Outer Harbor show that this species may grow from the zoospore to a length of 4 inches in as many weeks. After these plants have grown to 8 or 10 inches many of them, like the young plants of Ulva, are broken away from their supports and float about in the harbor, to finally grow into the great tangles that settle down on the Ulva and Zostera, sometimes covering dozens or scores 2? THE RELATION OF PLANTS TO TIDE-LEVELS of square yards of the bottom. In the more quiet areas the Hnteromorpha may form tangles of considerable size while remaining attached to the Zostera on which it germinated. The later history of these tangles of Hnteromorpha is similar to that of the sheets of Ulva. They are often floated up by gases accu- mulated in the cavity of the tubular thread. They then drift about the harbor, to lodge on some new part of the bottom and continue active growth, or they may settle on the beach or on top of Spartina glabra. On the south shore of the Spit masses of H. clathrata with some intermingled Ulva may crush down 75 or 100 square yards of Spartina, in some cases smothering out the rhizomes also and leaving a bare strip. Such tangles as lodge on the beach or on the salt reed-grass die and then break up and wash away or settle down to form part of the soil among Spartina stalks. Smaller bits of the living alga may settle on the mud between the Spartina stalks, or among pebbles on the beach above the Spartina, and there take part in the formation of the composite mats or felts of which other green or blue-green alge form the major part. Of its distribution there we shall have something to say when discussing the other alge of these higher levels. Despite the fact that it floats more readily because of the gases within its filaments, the freedom cf movement of Hnteromorpha is on the whole less than that of Ulva. Because of its filamentous form Hnteromorpha becomes more readily entangled with other objects on the bottom, and it is also more often weighted down by young mussels which become attached to it in thousands. On the bottom from the 6-inch to the 1.5-foot levels, where Zostera and mussels are usually wanting, the tangles of Hnteromorpha are also rare. The usual absence of Hnteromorpha lower than about 3 feet below mean low water seems also determined by the absence below this level of organisms such as Zostera and mussels, with which it may become entangled or weighted down. It is true that small mats of this alga are sometimes seen below the limit of the Zostera in the deep hole at 1,400 north, but these are apparently all in transit to or from the Inlet. Younger plants attached to stones are found all along the Inlet from 3 feet downward, some being found even in the deep hole. These plants must form an additional though relatively unimportant supply of free plants which may grow into tangles like the more numerous plants starting on the Zostera. Zostera marina: This “ eel-grass,’” because of its abundance, gives character to large areas of the harbor bottom at low tide, and also forms an important substratum on which grow several species of epiphytic alge. For this reason the region covered by a dense growth of Zostera has been indicated by a wavy outline on the map showing the topography of the harbor (plates 1 and xmir). The area so indicated is not by any means evenly covered with Zostera. In fact, many areas within this boundary which are several yards across may have but the barest sprinkling of this plant. Moreover, as is indicated on the map, there are numerous scattered or clustered and usually small plants of Zostera outside of this boundary. In the more vigorous patches of Zostera found in the Inner Harbor in July, the individual plants often have a rhizome 0.33 meter long and from 2 to 3.5 or 4 mm. in diameter. It is made up of 15 or 20 internodes, and runs along horizontally 1 cm. or more below the surface of the mud. Each rhizome terminates in a floral shoot, and bears from 2 or 3 to as many as 5 or 6 leafy lateral shoots. These lateral shoots may branch two or three times above the ENHALID FORMATION 23 mud, each of these branches consisting of from 12 to 20 short internodes, and bearing from 4 to 8 functional leaves. The width of these leaves varies from 5 to 8 mm. and the longer of them are from 1 to 2 meters in length. The fertile, or floral, shoots of Zostera, at this season, vary in length from 50 cm. to 1.5 meters. Each consists of about 15 or 20 internodes, which are from 1.5 to 2 mm. in diameter and from 5 to 20 cm long. Each node bears a leaf which is about 4 mm. wide and 15 cm. long. On older parts of the shoot nothing is left of the leaves but the sheath and perhaps a small bit of the blade. Inflores- cences in all stages of development are present on each fertile shoot, from floral rudiments just initiated at the top to spathes at the base from which the fruits have already been discharged. The densest stands of Zostera seen in the harbor are that east of the channel to the Outer Harbor, northeastward from 1,200 north by 800 east, those along the two banks of the tide-stream from 2,000 north by 400 west to the depression at 1,500 north by 300 east, and that on an area of several hundred square yards extent southwest of the deep hole about 900 north by 200 east. On these areas there may be from 500 to 2,000 leaf-clusters of Zostera to each square yard “ bottom. In other parts of ‘the Zostera region indicated on the map, e. g., much of the area near the main north-and-south axis from 1,000 north to 2, 000 north, the stand of Zostera is far less dense, with an average ‘of 200 or 300 leaf- clusters per square yard. For some distance outside the indicated area, espe- cially to the north and west, plants of Zostera are very infrequent, perhaps 20 to 100 small tufts to each square of the map, 7. ¢., to each 3,333 square yards. These tufts are mostly scattered and show but 2 or 3 to 10 or 12 leaf-clusters each. The extreme limit of distribution of Zostera is shown on plate x111 by the use of the letter Z, which is used as a symbol for indicating the position of outlying plants. These plants are usually small, being 1.5 to 6 dm. from the rhizome to tips of leaves, and their distribution varies somewhat from year to year. For example, numerous scattered plants of Zostera were found at 2,000 north by 0 to 600 east in 1905 and 1906. From 1907 on, following the occupation of much of this area by beds of mussels (Mytilus edulis), Zostera has been nearly or quite wanting here. The presence of the mussels has evidently led to a gradual silting over of the bottom of this area, raising it to or above mean low water, which is probably a direct cause of the disappear- ance of Zostera. It may well be that the mussels also cause other changes in the soil, making it injurious to the Zostera, e. g., in the content of such gases as air, CO,, or H,S. Such changes may explain the disappearance of Zostera from bottom not continuously occupied by mussels that has not yet been raised above the usual upper limit of this plant. Though the horizontal distribution may seem decidedly irregular (plate x111), especially the scattered marginal tufts, the distribution in depth is pretty con- stantly limited. It is found at levels extending from mean low water down to 3.5 feet below this. The parts of the harbor where Zostera occurs above the upper limit mentioned, are certain areas where bottom at 6 to 12 inches above mean low water is overflowed more or less at low tide by water from inflowing streams. For example, the southern prolongation of the Zostera area near 600 north by 400 east overlaps the mean low-water line very considerably, and scattered outlying plants of Zostera are found as far south as 300 north by 200 to 400 east or 275 north by 725 east, and even a few tufts near 210 north 24 THE RELATION OF PLANTS TO TIDE-LEVELS by 500 east and at the 1.5-foot level. It seems evident from what has just been said that Zostera is excluded from bottom much above mean low water by its liability to death from exposure at low tide. In those places where it exceeds this usual upper limit it is protected from desiccation by water from streams, which runs over it at low tide. The environmental factors determining the lower limit of the Zostera have not been distinguished with absolute certainty. So far as could be discovered, from a study of the relatively short lower margin of the Zostera area about the deep hole, this plant does not encroach on bottom lower than that indicated, because this lower bottom is sandy or shelly. Such soils, in this harbor, are nearly always bare, no matter what the depth. In the few places where Zos- tera seems to be growing on such bottom, the use of a sounding-rod usually shows that there is a softer subsoil of mud, an inch or two below the surface. It seems likely that the Zostera in these spots originally became established on a mud bottom which later, by some change in water-currents, was covered by a layer of sand and shell fragments. Only a few plants, which had very short, narrow leaves, were found growing on an apparently pure sandy bottom. Possibly the turbid water of this harbor may make the light supply inadequate at greater depths. In the clearer water of Casco Bay, Maine, Zostera grows on soft bottom 10 feet below low-water mark, also in Great South Bay, New York. A similar distribution of Zostera is found in Carmel Bay, California. C. H. Ostenfeld (1909) has found a similar relative abundance and size of the Zostera (growing, however, in much deeper water), on sandy and on muddy bottoms of the coast of Denmark. He states (p. 33) that on the bare, firm, sandy bottom there is only a sparse growth of Zostera with short, narrow- leaved shoots, which are free from growths of epiphytic plants and of animals. On soft, muddy bottom, on the contrary, he finds a dense pure growth of Zostera with larger and broader leaves, which latter are occupied by many - epiphytic diatoms, brown and red alge, and various animals, e. g., hydroids, mollusca, bryozoans, and ascidians. On pebbly bottom, where the interspaces between pebbles and boulders are occupied by softer soil, Ostenfeld finds a “mixed Zostera vegetation” in which, on certain areas, Zostera grows in the mud, while the pebbles give fixing-points for Fucus, Laminaria, and other coarse brown and red alge. Another type of mixed Zostera vegetation is that mentioned by Ostenfeld as occurring in brackish waters with bottom of sandy mud, and is characterized by the abundance of the green alge Ulva, E'ntero- morpha, Cladophora rupestris, Chetomorpha linum along with Chara, Toly- pella, Lamprothamnus, and also the seed plants Ruppia, Zannichellia, and Potamogeton pectinatus. This last type is the one that approaches most nearly, on the whole, to the Zostera vegetation of the harbor we are studying. Perhaps the most striking difference between the two is the absence, from our area, of the Characeew and Potamogeton. The similarity will be clear when we consider the distribution of the alge of the harbor bottom. In our harbor the differences in the character of the bottom, and so the presence or absence of Zostera, seem primarily due to the differences in the swiftness of the water-currents. The bottom of the deep hole, and of the channels north of it, is of sand or gravel and particles of shell, with a few bits of organic material, all of which may be seen shifting with the current when the tide is swiftest. The only fixed plants seen here were Ceramiums, ENHALID FORMATION oo Polysiphonias, Rhabdonas, Ulvas, etc., which, with their anchoring pebbles, were evidently in transit through the Inlet. From a careful consideration of the conditions existing in the deeper portions of the harbor, it seems evident that the absence of Zostera is in some way determined by the swift tidal currents rushing over these portions. As there is no reason to believe that this current acts directly on the Zostera, it seems clear that the current acts by forming an unstable and sterile bottom on which Zostera can not establish itself. A merely sterile soil we would expect to be conquered by the gradual extension of Zostera into it, with an accompanying accumulation of organic matter about its shoots. We must conclude, therefore, that the downward spread of Zostera in this harbor is prevented by a shifting of the soil so frequent as to make it impossible for the out-pushing rhizomes to establish themselves and thus bind the soil. , Ostenfeld, in his study of Zostera in Danish waters, found that the shoots are perennial, and the leaves remain green all winter. The winter leaves of plants growing on mud bottom do not attain as great a length as leaves developed in summer. A somewhat similar retardation of growth in winter seems to occur at Cold Spring Harbor. Since our observations were confined largely to the months of July and August, we can not speak with certainty concerning the activities of the Zostera in winter. On April 7, 1911, however, an abundance of Zostera plants was found with most of the leaves only 1 or 2 dm. long, and evidently young, but also with older leaves a half meter or more in length. Plants collected in about the same locality on July 11, 1911, had leaves 2 meters long. Many of these were dead and worn at the tip and seemed evidently more than 2 or 3 months old. Not many plants of Zostera were collected and measured in April 1911, but it seems probable, from the condition of the plants in the following July, that longer leaves would have been found by more thorough search in April. From all the evidence gathered we are led to conclude that while the longer leaves of Zostera plants may be torn off by waves and ice during the winter, the leaves of the more sheltered plants may often persist from fall to spring. This conclusion is strongly supported by the fact that the floral shoots certainly persist over winter. This is shown by the fact that floral shoots 90 cm. long and bearing fruits 3 to 4 mm. long were collected on April 4, 1913, by Dr. A. F. Blakeslee; also by the presence in early July of empty spathes on infloresences which higher up bear mature and young fruits and unopened flowers. On the Danish coast, according to Ostenfeld, the floral shoots are initiated in April and drop off the rootstock in the late fall. We are not prepared to suggest any causal explanation for this difference in behavior of the Zostera in these two localities, unless it be the more destructive effect of winter waves in the more open water where Ostenfeld’s plants grew. In brief summary of the facts concerning the distribution of Zostera in the Inner Harbor, we can say Zostera commonly occurs on bottom between mean low water and 3 feet below this. In one or two areas flooded by streams at low tide, a dense stand of Zostera may grow on bottom a few inches above mean low water. The extreme upper limit at which Zostera was found—a few plants only—is 1.5 feet, and the extreme lower limit is —4.5 feet. The species is almost entirely confined to muddy bottoms. The part played by Zostera as a substratum for epiphytic alge will be noted in discussing the distribution of the alge. 26 THE RELATION OF PLANTS TO TIDE-LEVELS Ruppia maritima: This comparatively diminutive and delicate species is the only seed plant besides Zostera that is found on the bottom of the Inner Harbor below 1.5 feet. The characteristic mature plant of Ruppia, as it occurs in this harbor, is about 25 cm. long, and of 10 to 12 internodes varying in length from 20 to 70 mm. It has 8 to 10 functional leaves each 20 to 60 mm. long and 1 mm. wide. The plants flower freely at Cold Spring Harbor during July and August, but the stalk of the infloresences is short, rarely more than a few em. long, and therefore the flowers are not at the level of the water-surface except for about half an hour at the rise of the tide and a lke interval at its fall, 7. e., when the water-level is between 6 inches and 1.5 feet above mean low water. The plants flower and apparently fruit freely, as seedlings are rather frequently found. While Zostera is characteristic of an area lying below mean low water, Ruppra is practically confined to a vertically narrow belt between mean low water and 1.25 feet. The extreme limits are —0.5 foot and +1.5 feet. Though the vertical distribution of Ruppia is thus very limited, its horizontal distribu- tion is quite wide. At its lower limit, near mean low water, Ruppia is found mixed with scattered Zostera, but it is also scattered abundantly over areas near the 1.5-foot level, where Zostera is entirely wanting, e. g., 1,300 to 1,600 north along the east shore. Nowhere does the stand of Ruppia become as dense as the denser stands of Zostera, and, in fact, areas where the bottom is actually covered by Ruppia are small and rare. This is due not only to the relatively small number of plants, but also to their delicacy. The areas where Ruppia is most abundant are those with a soft bottom, bare of Ulva and usually protected from currents and waves. Such areas are those indicated on plate x11. They are found chiefly in the western and northern parts of the harbor, but there is another such habitat with abundant Ruppia along the eastern shore behind the Zostera belt. The horizontal distri- - bution of Ruppia is, in other words, limited to areas of quiet water and the fine, muddy soil formed in such areas. The vertical distribution of Ruppia, on the other hand, seems clearly determined by tide-levels. The lower limit of this species, as we have seen, is mean low water, or a few inches lower in exceptional cases, and the upper limit is at 1 foot, or more rarely at 1.5 feet, above mean low water. That is, the plant never occurs where constantly submerged, but rather on areas which are exposed for from 0 to 4 hours each day, depending on the magnitude of the tide. It seems clear that competition with other species can not be an important factor in keeping Ruppia out of soils at lower levels, since Ruppia does not occur on bottom below mean low water that is bare of Zostera and Ulva. The character of this bottom is apparently identical with that on which Ruppia is growing a foot or two higher up. There seems to be no difference in the conditions at these two levels, except in the relative duration of submergence and exposure. The upper limit of distribution of Ruppia may be determined in part perhaps by competitors, e. g., Spartina glabra, in the shade of which Ruppia occasionally grows at its upper level. It seems more probable that Ruppva does not flourish above the 1-foot or 1.5-foot level because unable to withstand the exposure to desiccation by air and sun at low water. This view is supported by the fact that Ruppia is most abundant in areas where it is kept wet by little rivulets that run over the mud at low tide, e. g., along the edge of the tide-stream at LITHOPHILOUS BENTHOS Lak 2,000 north by 200 to 400 west. The same is true even if the water moisten- ing the plants at low tide is fresh water, e. g., at 1,300 to 1,600 north by 1,000 to 1,075 east, or near the mouth of the creek at 200 north by 400 to 600 east. B. ATTACHED ALGAD OF THE HARBOR BOTTOM (THE “ LITHOPHILOUS BENTHOS ”). Under this head we include alge attached to stones, shells, or stakes below the 1.5-foot level, the “ Lithophilous Benthos” of Warming. Many specimens of these same species may be broken off and found drifting about the harbor entirely free of any support. Though 18 or 20 species of algee may be found on the bottom of the harbor, only 7 or 8 of these, including the Ulva and Entero- morpha clathrata mentioned above, occur in any considerable numbers. Even these are not at all abundant except in the Inlet, or, in the case of three or four species, along the streams entering the harbor. The species that have been found on the bottom at one time or another are: Beggiatoa mirabilis, Oscillatorva sp?, Cladophora (expansa?), Enteromorpha clathrata, HE. intestinalis, Ulva lactuca, Ascophyllum nodosum, Hctocarpus stliculosus var. amphibius Harv., Fucus vesiculosus, Pylaella littoralis, Scyto- siphon lomentarius, Agardhiella tenera, Callithamnion roseum, Ceramium rubrum, Chondria tenuissima, Chondrus crispus, Dasya elegans, Delesseria leprieuru, Gracilaria multipartita, Grinnellia americana, Hildenbrandia prototypus Nardo, Petrocelis cruenta, Polysiphoma variegata, Porphyra lacimata. In discussing the occurrence of these alge we may take up in some detail the distribution of the more abundant species in each class, and then note briefly the information that we have been able to gather concerning the occurrence of the rarer or occasional forms. SCHIZOPHYTA. Beggiatoa mirabilis occurs commonly on the surface of the black mud of the bottom, from below mean low water up into the present belt, and also, as we shall see, still further up, to the 6 or 7 foot level, in tide-pools, or in trickles of salt water at the edge of the estuarial marsh. Osctllatoria sp? was found only infrequently coating the surface of dead fronds of Fucus in the Inlet, at about mean low water. CHLOROPHYCE. Of the green algee enumerated above we have already noted the distribution of attached plants of Enteromorpha clathrata (p. 21) and Ulva (p.18). The only remaining species are Cladophora (expansa?), Enteromorpha intestinalis, and Ulothrix flacca. In April 1911 tufts of Cladophora (expansa?) 3 or 4 cm. long were found frequently along the Inlet near mean low water at 1,800 to 2,000 north. In September 1911 similar tufts were frequent in the creek, at 200 south, between the 1 and 2 foot levels. Considerable mats of it are found each summer tangled with Zostera and with other alge in the middle of the harbor bottom, where it also occasionally appears as an epiphyte on Zostera (plate vir). At this season it is much more abundant at higher levels, as we shall see later. 28 THE RELATION OF PLANTS TO TIDE-LEVELS The large, simple, tubular fronds of Hnteromorpha intestinalis are likewise characteristic of higher levels, especially in the neighborhood of fresh-water streams. Along these streams, however, when they are large enough to reach to the low-tide mark as single streams, we sometimes find the Hnteromorpha accompanying them downward to within the limits of our zone. For example, at 20 south by 590 east, beside the main stream at the head of the harbor, at the 1.5-foot level, H. intestinalis is usually quite abundant and of good size, though neither as abundant nor as large as it is, at somewhat higher levels, a few feet south of this. A very interesting patch of this Hnteromorpha is that growing on the bottom near 1,440 north, on the east shore. At this point the overflow pipe from an artesian well penetrates the wall of the wharf at the 4-foot level. At low tide the water from this pipe falls to the bottom, which is at about the 1.5-foot level, where the water splashes down upon pebbles and stones, and then runs off over the bottom toward low-water level. A circle of the bottom 4 feet in diameter, round about the point where this stream strikes, is covered by hundreds of plants of Hnteromorpha intestinalis, from 5 to 20 mm. in diameter and 2 or 3 dm. in length. A few dozen plants are found scattered along the stream running from this circle down over the bottom, but this latter area is dominated by Ascophyllum. Near another fresh-water outlet 100 feet north of this we have a similar sparse sprinkling of this Hnteromorpha which does not dominate any appreciable area. The factors affecting the distri- bution of Enteromorpha intestinalis will be mentioned in discussing its distribu- tion at higher levels, where it is more abundant. Ulothriz flacca was found but sparingly below the 1.5-foot level in April 1911, though it was everywhere abundant just above this. PHAOPHYCEA. Ascophyllum and Fucus: What has just been said of the relative abundance of Enteromorpha in this belt is true also of Ascophyllum and its relative Fucus, two genera which, because of their similarity of distribution, may be discussed together. ‘These alge attain their greatest abundance in the next higher belt of vegetation, in the harbor, from 1.5 to 6 feet. (See plate 1x.) The rela- tively few plants found below the 1.5-foot level grow on stones, chiefly along the channel to the Outer Harbor or along that from the Creek. Occasionally plants or clumps may be found on stones or sunken logs along the shores of the harbor. Near the middle of the harbor these alge are rarely found, and then they are attached to small pebbles or shells which they have evidently dragged with them from higher levels in the Inlet. From the distribution of Fucus and Ascophylium found in the Outer Harbor, it is evident that these plants may grow abundantly at, and somewhat below, low-water mark. It is therefore probable that the sparseness of these algee below the 1.5-foot level in the Inner Harbor is due in part to the absence below the bases of the wharves of any proper substratum for their attachment. The abundance of shifting Ulva is another important factor, for these sheets would be sure to bury the relatively slow-growing rockweeds before they could attain any considerable size. Ectocarpus siliculosus var. amphibius: This form has been found below the 1.5-foot level in only one locality, near a deep portion of the channel of the LITHOPHILOUS BENTHOS 29 main stream, at 150 south by 780 east. Just upstream from this depression (160 south), the pebbly bottom slopes sharply down from a 1.5-foot level to —0.5 foot in the deepest parts of the depression, and then rises to about 1 foot at the northern end of the hollow. In the bottom of the deepest part of this depression, and still more abundantly in the little rapids above it, the Ectocarpus grew in luxuriant tufts, with numerous gametangia, in the early summer of 1911. In late August of this same year it had practically disap- peared. The water flowing over this alga during 3 to 5 hours of each tide, or 6 to 10 hours per day, is entirely fresh, while for the remainder of the tide the plants are surrounded by salt water. Moreover, the change from one to the other is quite rapid, which shows that the alga is capable of withstanding marked and sudden changes in the osmotic quality of the surrounding medium. Scytosiphon lomentarius: This alga occurs in the Outer Harbor all summer and unattached small tangles of it are found scattered over the bottom of the Inner Harbor at this same season. Only in early April 1911 did we find it attached in the Inner Harbor. At that time it was sprinkled in frequently among Ulva, Enteromorpha clathrata, Porphyra, and Pylaiella, on the stony bottom east of the channel of the Inlet, at 1,900 to 2,100 north and from mean low water up to the 1-foot level. These plants were 30 cm. long, about 1 mm. in diameter, and were fruiting. Pylaella littoralis: This densely branched filamentous brown alga has been found nearly every summer at one or more spots about the harbor. It is usually present, for example, in the deeper part of the Creek at 150 south at —0.5 to +1.5-foot levels. It was abundant in the Inlet in July 1912, but had largely disappeared by September. It is sometimes found also on the shady sides of piles or stones on the wharf of the Research Laboratory, chiefly, though not wholly, above 1.5 feet. In 1912 large tufts grew where splashed by fresh water at 150 north and 500 north on the west shore. In April 1911 this alga was probably the most abundant species about the harbor from mean low water up to 3 or 4 feet. At half tide its dense tufts could be seen everywhere, often as much as 1.5 dm. long. They were attached to pebbles, shells, stones, wood, and even tangled among the stalks of the Spartina glabra at its lower levels. All of these plants were either sterile or had chains of zoosporangia. On September 29, 1911, this same alga was found on pebbles in the deep part of the main stream at 150 south and in the rapids just above this at 200 south. In the plants collected at this time the only reproductive organs seen were gametangia, which had not been seen at all on plants collected in April or in midsummer. From what we have noted it is clear that Pylaiella, like Hctocarpus stliculosus, is capable of enduring the rapid change from salt to fresh water and the reverse which occurs in the main stream with each change of tide. It is also noteworthy that while this alga is very abundant and widely distributed about the harbor in April, it is represented in summer by only a few groups of plants in areas protected from high temperature and desiccation. The fact that the plants found in spring and early summer bore zoosporangia only, while those found in September bore only gametangia, suggests the probability that this alga really has a distinct seasonal alternation of a spore-bearing period with a gamete- bearing period. It may even prove to be an alternation of distinct asexual 30 THE RELATION OF PLANTS TO TIDE-LEVELS and sexual generations, comparable with that of Dictyota and that of the red alge Polysiphonia and Griffithsia. (See Lewis, 1914.) The vertical distribution of Pylaiella thus far recorded extends from —6 inches up to 5 or 6 feet. That is, it occurs both in areas where it is nearly always submerged and also, on shady spots along wharves, where it is exposed to the air from 8 to 9 hours each tide. It seems evident that this alga is not able to go higher on the wharves, nor, in most places, even as high as here recorded, because of the danger of desiccation during low tide. It perhaps does not grow on bottom below mean low water at the Inlet because of the swift current which runs over the bottom, sweeping along pebbles, shells, and dislodged alge. Why, if it can endure long submergence in fresh water, it does not push further up the fresh-water streams, it is not easy to understand, unless it be its inability to endure continuous submergence in fresh water. Pylatella would probably prove a good subject for experimental determination of the effect, on the distribution of alge, of such conditions as high temperature and exposure to fresh water and to dry air. THE RHODOPHYCE. Of the 13 species of this group of alge growing on the bottom of the harbor, the most important are Chondrus, Porphyra, and the incrusting alga Hilden- brandia. We will discuss these first, and then take up the remaining forms in alphabetical sequence. Plate 1x shows the distribution of the most frequent of the Rhodophycez about the harbor. Chondrus crispus is usually the most abundant red alga in the harbor, after the Ceramiums, Hildenbrandia, and perhaps Bostrychia. It occurs abundantly in the Inlet during the summer, chiefly on the pebbly bottom east of the channel, between 1 foot below and 1 foot above mean low water. In July 1911, for example, Chondrus was distributed over a strip varying from 10 to 40 or 50 feet in width, and stretching from 1,700 to 2,000 north. The plants found here are from 0.5 dm. to 1 dm. in height, and form dense tufts of a reddish or brownish color. They are apparently quite as vigorous and fruit quite as freely as plants growing in open water in the Outer Harbor or in Long Island Sound. Two or three smaller plants were found at 1,600 north near mean low water. These were the southernmost plants ever recorded. Though this alga is one of the most constant in occurrence and distribution during each summer, it could not be found after careful search along the Inlet in April 1911. On September 28, 1911, this species was not seen, though searched for as carefully as possible, when the water was at the +1-foot level. Porphyra laciuniata: This is the only red alga found on the bottom of the harbor in April 1911. It was then nearly as abundant and widely distributed as Ulva, except that it was never found in or near fresh-water streams. ‘The Porphyra was then most abundant east of the channel to the Outer Harbor, from 1 foot below to 1.5 feet above mean low water. The individual plants at this point were often 2 to 3 dm. long, and about as broad. In other parts of the harbor, in April, the Porphyra is sprinkled about somewhat generally, though not abundantly, chiefly on wharves and wrecks between the 2-foot and the 4-foot levels. Hundreds of sheets of this alga, usually 1 to 2 dm. across, but sometimes larger, were seen in April among the stubble of the Spartina glabra along the west shore. Closer examination showed that the vast majority LITHOPHILOUS BENTHOS 31 of these were detached, only a few dozens of them being attached to mussels. The only source that could at this time be discovered for such numbers of the plants of Porphyra was the dense colony of them in the Inlet. With so many detached plants about the harbor it is interesting to note that they do not settle on the bottom to cover large areas, as Ulva does. This is evidently because the Porphyra floats and is therefore cast up on the beach instead of settling. Porphyra is noticeably free from epiphytes, probably because of its lubricous surface. In the summer Porphyra is relatively rare in the Inner Harbor, though it is still abundant at various points in the Outer Harbor. The plants found in our area 1n summer are chiefly on the wharves, between 2 and 4 feet, and their distribution at these levels will be noted in discussing the rockweed association. The factors determining the distribution of Porphyra are not very clearly indicated by its occurrence in the area under observation. The limits noted in April and July, 2. e., —1 to +4 feet, are very nearly the limits of distribution of the plants found on the open shores of Long Island Sound. From the observa- tions here made it seems evident that cool water, stirred by waves or tidal currents, furnish the conditions favoring the growth of Porphyra. The upper limit seems to be determined by the time of exposure to the air, and the lower limit probably by the lack of light due to the turbidity of the water. It seems hardly probable that a delicate alga of a single layer of cells can be confined to levels above low tide, because of the need of exposure for aeration. Hildenbrandwa prototypus, an incrusting species, is more widely spread in summer than any other red alga of the Inner Harbor. It occurs on pebbles and stones at all levels from mean low water up to 6 or 6.5 feet and wherever there is a proper substratum. It grows both in pure salt water and in places where the plants may be overflowed for several hours at each tide by fresh water. For example, it is found abundantly on pebbles along the channel to the Outer Harbor from mean low water up to 1.5 or 2 feet, and on the shoals beside the Creek, at 470 east and 625 east at 1 to 2 feet, and, finally, it occurs within the present belt on stones of the wharf of the Research Laboratory, and of the wharves east of the Inlet at 2,200 north to 2,600 north. The distribution of this alga at higher levels and the factors determining its upper and lower limits will be discussed in describing the next higher belt of vegetation. The remaining ten species of Rhodophycee found on the bottom of the harbor are usually represented by few dozens or scores of individuals each. In fact, one or more of the species may be entirely wanting in some summers. Some of these ten species may develop in situ, on stakes or buoys, or on stones of the bottom. Others are rarely found fixed to a stable substratum. More often they are found drifting about over the bottom, being either entirely free or dragging about with them small pebbles or shells which hold the young plants in place, but which are too small to anchor securely the now full-grown plants. The ten species to which we have referred are: Agardhiella tenera, Callithammion roseum, Ceramium rubrum, Chondria tenuissima, Dasya elegans, Delesseria leprieurtt, Gracilaria multipartita, Grinnellia americana, Lomentaria uncinata, and Polysiphonia variegata. Of these alge Callithammion and Lomentaria have each been found during one season only, when a considerable number of plants of each were established in the Inlet, near 2,300 north by 1,175 east, at about mean low water. 32 THE RELATION OF PLANTS TO TIDE-LEVELS Agardhtella is a coarse and rather cartilaginous species which is found abundantly in parts of the Outer Harbor and which often drifts into the Inner Harbor. It has not been found within our limits fixed to anything larger than small pebbles which are dragged about by the stiff, bushy plants. In some seasons dozens of these, and still larger numbers of entirely free plants, are tumbled about over the bottom, below the 1.5-foot level. Ceramium rubrum is abundant on Zostera in the Inner Harbor and is also found occasionally on pebbles or shells in the Inlet at 2,300 north by 1,000 to 1,200 east at mean low water and below. Its relative, C. strictum, has not been found, except on Zostera. Chondria also has been recorded but once since our work began (in July 1908), though it was often seen in earlier years in the same place,—2,200 to 2,300 north, on the east side of the Inlet, at about the —1-foot level. In the one case recorded carefully the plants were about 1 dm. high, and all of them were tetrasporic. During the early years of this study Chondria was abundant in the Outer Harbor just outside the Inlet. At these times floating plants of Chondria were common in the Inner Harbor. The fixed plants outside the Inlet have disappeared almost completely during the last few years, and with them, of course, the free plants in the Inner Harbor. No cause has been discovered to which this disappearance of the Chondria, and of other red alge also, can be attributed with certainty. It seems probable that it is related to the sudden covering of large areas of the bottom by mussels which occurred in 1907. Perhaps the greater rarity of certain alge of the Inner Harbor in recent years is due to the greater distance over which the spores must come from areas outside it, where the plants are abundant and constantly present. It seems evident that fewer of the spores can reach the Inner Harbor from an _ area 2 or 3 miles away than from one 200 or 300 yards away, though as a matter of fact we have no certain evidence of the endurance of these spores or of their ability to remain afloat for so long a time. Delesseria is a smoky green, inconspicuous alga that has been found only once within the limits of the belt that we are discussing—at 1,750 north by 1,070 east at the 1-foot level. It is more frequent at slightly higher levels, as we shall see later. Gracuaria is found in small numbers attached to pebbles and shells at levels between —2 and +1.5 feet on the bottom of the Inlet. It is sometimes also found being washed about over the bottom of the harbor, either entirely free or else dragging about with it the small pebble or shell on which it has grown. Both attached and free plants of Gracilaria have become less frequent of late years, probably for reasons identical with those suggested in speaking of Chondria. Grinnella is a broad, sheet-like alga which is quite frequent in the Outer Harbor. When our work began attached plants of it were abundant every summer in the shallow branch of the Outer Harbor directly north of the Inlet. © In 1906 three or four attached plants were found near 175 north by 625 east. These in all probability had been carried in by the tide and had dragged their small supports with them. Our records for 1907 show that half a dozen attached plants of this species were found in the Inlet between 2,200 and 2,400 north near mean low water. Plants which are entirely free are still found drifting over the bottom of the harbor, but while in earlier years these could be seen by LITHOPHILOUS BENTHOS oo the score, in 1909 and 1910 only a dozen or fifteen could be found in the whole harbor. Not half a dozen attached plants have been seen in the Inlet or Inner Harbor during the past two years. The filling up of the area of the Outer Harbor just north of the Inlet, which is correlated in some way with the abun- dance of mussels, has driven Grinnellia out of the area where it was formerly abundant, and from which the Inner Harbor could be readily supplied with spores and drifting plants. It is clear that in this, as in the case of the other red alge mentioned, we can not know with certainty the explanation of their distribution in the summer until we know more of their distribution and activi- ties during the other seasons of the year. Polysiphonia is abundant in some seasons on pebbles on the bottom of the Inlet from 2,000 to 2,600 north, between mean low water and —3 feet. Tetra- sporic plants are common in summer, while cystocarpic and antheridial ones are usually rare. In late September 1911 this alga was far more abundant than it has ever been in midsummer on the bottom of the east side of the Inlet from mean low water downward. In the region between 2,000 and 2,200 north, which was most carefully examined at this time, there were often 10 to 15 dense tufts to each square meter. All of these plants that were examined proved to be sexual, chiefly cystocarpic. In most summers a few drifting plants of Poly- siphonia are found in the Inner Harbor, some of them attached to small pebbles. In other summers these and the attached plants of the Inlet are practically wanting. When, therefore, we find in some succeeding summers a relatively large number of these plants in the Inlet, we are inclined to conclude for this species, as for the others mentioned above, that the new plants must come from spores brought in from the Outer Harbor, rather than from any perennating portions of plants of a former summer left in the Inner Harbor. The great abundance of this species in September 1911, however, suggests the possibility that its basal portions may be constantly present, but that its shoot is well- developed only in occasional summers, when conditions are unusually favorable at that season. The free or drifting plants of the red alge of the Inner Harbor that have been noted above may in some species remain in the living condition but a short time. Such, e. g., is usually the fate of the Ceramiums, Chondria, Dasya, and Polysiphonia. Other species, on the contrary, like the green alge Cladophora and Hnteromorpha, may persist indefinitely and even continue to develop. Thus, e. g., when Agardhiella, Gracilaria, and Grinnellia lodge on the bottom near low-water mark, they may continue to produce tetraspores or cystocarps for weeks after being torn loose from their substrata. In this way, of course, spores of alge not before growing in the harbor may be dispersed about it in considerable numbers. C. EPIPHYTIC ALGA ON ZOSTERA AND ULVA. About 7 or 8 species of the alge of the Inner Harbor are attached to other plants, chiefly to Zostera. In fact, it is the presence of Zostera, to serve as a substratum, that alone makes it possible for most of the epiphytic species to grow at all abundantly in the Inner Harbor. It is because of this importance of Zostera as a substratum that we have indicated its distribution on our topo- graphic map of the harbor. 3 34 THE RELATION OF PLANTS TO TIDE-LEVELS The species of alge which frequently occur as epiphytes on Zostera, on Ulva, or occasionally on other alge, are the following: Spirulina tenuwissuma, Cocconeis scutellum, Melosira borre, M. nummuloides, Navicula greviller, N. kennedyi, Synedra affinis, Cladophora (expansa?), Enteromorpha clathrata, Ceramium rubrum, and C. strictum. (See plates vir and Ix.) Among these epiphytic forms there is no general predominance of any one species, though because of their size and color the Ceramiwms may be more prominent. We may therefore discuss the species enumerated in alphabetical order within each class, beginning with the simplest. SCHIZOPHYCEZ. Spirulina tenuissima: This alga, as we shall see later, is widely spread from mean low water up to the 7-foot level, but it is in the present belt, as an epiphyte on Zostera, Ulva, and sometimes on Hnteromorpha clathrata, that it is most luxuriantly developed. On the Zostera this alga sometimes forms dense yellowish-green patches, sparkling with gas-bubbles and often many square decimeters in extent. For example, in 1910, patches of this sort were thickly sprinkled over hundreds of square meters of bottom from 1,300 to 1,500 north by 950 to 1,050 east, covering one-third of the Zostera plants and matting scores of their leaves together. Similar, though usually smaller, patches of Sprrulina have been seen adhering to the large sheets of Ulva or on tangles of Hnteromorpha clathrata in the southeastern parts of the harbor. Still smaller patches occur occasionally on stakes or buoys in the middle of the harbor. These patches of Spirulina are 5 to 10 mm. thick and practically pure, showing but few other organisms within the mass, such as filaments of an Oscillatoria or of some other epiphyte of Zostera buried by the growth of the Spirulina. These dense growths of Spirulina are confined, in this harbor, to levels within a foot or less of mean low water. At higher levels, up to its upper limit at about 7 feet, Spirulina occurs sparingly mixed in mats or felts with numerous other Cyanophycesx, none of which seem to flourish near mean low water, where Spirulina does best. The lower limit of Spirulina in this harbor is about 1 foot below mean low water, and it is apparently conditioned by the presence in somewhat quiet water, which gets warm at low tide, of a substratum such as Zostera or Ulva over which it may spread. In its occupa- tion of substrata at higher levels it is restricted probably by the danger of desiccation, except in shaded areas or where it is protected by mats of other algw. Probably at higher levels also, in some localities, it is kept lower than usual because of lack of a suitable substratum. BACILLARIALES. The epiphytic Diatomee of the bottom of the harbor include the most abun- dant and widely distributed epiphytes of this belt. Cocconets scutellum, e. g., is found, often in great numbers, on nearly every plant growing in the Inner Har- bor. It grows not only on Zostera, but even more abundantly on Ulva and on both attached and free plants of other larger alge. It is often especially abun- dant on the epiphytic Ceramiums. The distribution of this diatom has not been studied in great detail, but it apparently occurs on all living substrata through- out the harbor, except near fresh water. In vertical distribution Cocconets is found from —2 feet to +1.5 feet. EPIPHYTIC ALGH ON ZOSTERA, ETC. Sys) Melosira borres and M. nummuloides: These diatoms, though less abundant, are even more widely distributed over the harbor-bottom than Cocconets, since they endure submergence, for several hours at least, in entirely fresh water. They are best developed, however, on the long leaves of Zostera or on stakes or buoys in the middle of the harbor. Here they form tufts of a rusty brown color from 2 or 3 to 25 or 30 mm. in diameter and from 4 or 5 to 25 or 30 mm. in length. The distribution of these tufts is somewhat more restricted than that of Zostera. They are present in considerable numbers only on the larger, denser Zostera near the center of the harbor. On outlying Zostera, as well as on Ulva, Enteromorpha, Pylaiella, and on several of the Floridexe of the bottom, Meloswra is found in single threads or clusters of few short filaments. Apparently all these Melosira tufts of the bottom and those along the Creek to 200 south are of the same species and are identical with those which occur mixed with Cyanophycese and Chlorophycee on marsh and beach at higher levels. The distribution of Melosira tufts is limited primarily by that of the plants on which it grows. It is evident, however, that though Melosira does not grow in the swiftest currents, it is most luxuriant where there is a considerable movement of the water, e. g., at the sides of the deeper channel leading from the Inlet toward the Creek and near the tide-stream entering the deep hole from the northwest. The abundance of Melosira on the Zostera, just aside from the swiftest current, where the Inlet opens into the Outer Harbor, confirms the conclusion that frequent change of the surrounding water is distinctly advan- tageous for this diatom. Navicula grevillei and N. kennedyi: These species have much the same dis- tribution as Melosira in the middle of the harbor, and are even more abundant and more luxuriant than Melosvra on the denser Zostera. The tufts of these Naviculas are distinguishable from those of Melosira by the somewhat lighter color, the slippery feel, and the abundant branching, as well as by the iridescent character of the gelatinous matrix in which the frustules are embedded. Synedra affinis: 'This is another diatom which is widely distributed on many hosts. It was especially abundant on Pylaiella in the Inlet on April 8, 1911, and on Pylatella and Enteromorpha intestinalis, in the Creek at 200 south in September 1911. On many branches of the Pylavella these diatoms stand out so thickly as to make these branches look lke diminutive chenille cords. There are of course other epiphytic diatoms (see list on p. 161), but those mentioned are the most abundant and widespread in distribution. CHLOROPHYCE. The only important epiphytic Chlorophycee are Chetomorpha erea forma linum, Cladophora (expansa?), and Enteromorpha clathrata. Chetomorpha erea: Though this is originally epiphytic, it is found most frequently lying on the Ulva or tangled with Zostera, Cladophora, or Entero- morpha on the bottom, near the middle of the harbor. What is apparently the same species is found at higher levels among the Spartina glabra. Cladophora (expansa?): This is a species which is rather frequent in little tufts attached to Zostera near the deep hole, though far less abundant than its fellow-epiphytes Hnteromorpha clathrata and the two Ceramwms. The tufts of Cladophora are 2 or 3 cm. long and are made up of repeatedly branched and. densely interwoven filaments. 36 THE RELATION OF PLANTS TO TIDE-LEVELS Enteromorpha clathrata: The occurrence of this species as an epiphyte we have already mentioned when referring to the long, streaming tufts of it on the Zostera as the source of the loose mats of this alga that drift over the bottom. We may here emphasize the fact that it is very abundant as an epiphyte. Often a dozen large tufts of it may grow on a single leaf-cluster of Zostera, and the filaments may attain a length of several decimeters before being set free, which usually occurs by the rupture of the supporting leaf. H. clathrata also has a wide distribution. It is the only noticeable epiphyte on the outlying clumps of Zostera, except a few tufts of Melosira. RHODOPHYCE. As indicated in our enumeration of species, only two epiphytic red alge © have been found in the harbor, and both belong to the genus Ceramium. Though Polysiphonia occurs as an epiphyte on Zostera in other Long Island waters, mature plants of this species never have this habit in our harbor. Melobesia, another epiphyte found in more saline waters about Long Island, does not occur here at all. Ceramium rubrum: This alga‘ forms dense tufts, 5 to 10 cm. long, on the leaves of Zostera. Dozens or scores of these large tufts may sometimes be seen on each square meter of the Zostera, and in such areas this Ceramium is the most prominent epiphyte. This alga is most abundant just aside from the swiftest current along the Inlet, about the deep hole, and beside the tide- stream entering the latter from the northwest (plate Ix). Evidently this red alga, like Melosira, flourishes best in moving water. In fact, the Ceramiwm fails to accompany the Zostera to the limit of its distribution, the outer or upper third of the Zostera being bare of the alga. Some of the plants of this Ceramium found in July and August bore tetraspores and others cystocarps or antheridia. Ceramium strictum: This is the only red alga of the Inner Harbor which has . been found here solely as an epiphyte. It is somewhat smaller in size and brighter in color than C. rubrum. The distribution of C. strictum is in general similar to that of C. rubrum, but it is evidently still more closely confined to the Zostera immediately surrounding the deep hole and the tide-stream flowing into it from the northwest. } So far as has been determined from a study of the epiphytic alge of the harbor bottom, a study which has been concerned especially with the Ceramiums, these alge are found at levels where they are submerged at all but the lowest tides. They evidently will not endure long exposure to dry air. The absence of the Ceramiums from the Zostera growing in the area from 500 to 700 north by 200 to 600 east indicates that these alge can not endure submergence in the brackish, and for part of the time actually fresh, water which flows from the Creek at low tide. 3. THE MID-LITTORAL BELT (1.5 TO 6.5 FEET). As one looks about the harbor at low tide the whole natural shore for some distance below high-water level is seen to be occupied by a very clearly marked — belt of vegetation of quite uniform character. Closer examination shows that the sole conspicuous plant of this green belt is the salt reed-grass Spartina glabra var. alterniflora, and that it really occupies the middle portion of the strip of muddy shore between the two tide-marks. In fact, except where PLATE Ill with 00 North X 500 East, 2 ’ 2 near b) a Ge losus spira va glab Spartir Cus VES A. Lower Edge of Zone of 1s. 1 wu Fu ith Upper Part of Belt of Fucus and yllaam U WwW ide, Sc 00 North on East S aUet.6 td B. Wall D oph A % PEATE IV A. South Shore of Spit looking Eastward from 100 West, showing Upper Margin of Spartina glabra alternifiora (at right), Sueda (in center middle distance), and at left Ammophila, Solidago, and Ailanthus. The tide stakes are at 7, 8, 9 and 10 feet respectively. B. Portion of East Shore just South of Mill (400 to 500 North), showing Spartina glabra alternifora and Scirpus americanus (left foreground). Sambucus and Ailanthus (center background), Solidago sempervirens and Iris versicolor (right foreground and middle distance). . = : > 1 -_ 7 MID-LITTORAL BELT at local conditions of soil-moisture or shade are unusual, this grass is confined to levels between 1.5 and 6.5 feet. On the mud with the Spartina are found one other seed plant, Lilwopsis, and numerous alge, mostly small and incon- spicuous, except where matted together in numbers. If the observer now turns to the portion of the harbor’s edge bounded by wharves, he finds the stone walls and piles between tide-marks occupied by a belt of brown rockweed. Closer examination of these areas shows that they also are generally confined between the 1.5 and 6.5-foot levels, and that, though numerous other alge may be found here, the areas are dominated by the rock- weeds Ascophyllum and Fucus. These two types of vegetation, found between 1.5 and 6.5, we may designate as the Mid-littoral Marsh and the Mid-littoral Rockweed Association respectively. Together they bound practically the whole circumference of the harbor. The only breaks in this distinct belt or zone are the. stream-beds and two or three short stretches of artificial gravel beach. A. THE MID-LITTORAL MARSH. This belt, as has just been indicated, is a Spartinetum, dominated com- pletely in most areas by Spartina glabra. It evidently corresponds in many respects to the “ salt-reed swamp ” of Warming (1909, p. 223). There are two striking features of this marsh at Cold Spring Harbor. In the first place, there is no admixture of other seed plants save half a dozen small patches of Lileop- sis and a few scattered migrants from the next higher belt, which wanderers, except near fresh-water streams, never get more than a few inches below the 6-foot level.* In the second place, this Spartina lies exactly in the middle of the “littoral region,” if, with Kjellman (187%, p. 57) or Oltmanns (1905, p. 167), we define this region as that lying between the two tide-marks. Kjellman chooses the extreme upper and lower tide-marks as the boundaries of this littoral zone, on the west coast of Nova Zembla. But at the place where he worked the range of tides is small and the maximum range differs but little from the mean range. In the harbor we are dealing with the mean tide-limits have been chosen as boundaries for the littoral belt because the extreme range of tides is much greater than the mean, and because this choice gives us a belt characterized by distinct vegetational types. At Cold Spring Harbor, where mean high water is about 8 feet above mean low water, and where the Spartinetum lies between 1.5 and 6.5 feet above mean low water, this association seems very aptly named the Mid-littoral Marsh. Moreover, from observations made elsewhere on Long Island and on Casco Bay, Maine, we are led to believe that the salt reed-grass along our whole North Atlantic coast will be found to be located just about midway between the mean tide-marks. We believe the name here used may be found generally applicable and clearly descriptive, for this Spartina association, wherever its vertical distribution is accurately determined. In our detailed discussion of the vegetation of the Mid-lttoral Marsh we will first consider the distribution of the Spartina and the other seed plants that are associated with it in its upper portions, and then take up the distribution of the algal felts or tangles and more scattered alge which form “ subordinate communities ” on the bottom between these seed plants. * Scirpus nanus also has been seen below the 6-foot level in a few places on the Marsh. 38 THE RELATION OF PLANTS TO TIDE-LEVELS 1. THE SPARTINA GLABRA ASSOCIATION. In discussing the character and distribution of this association it will be best, because of the differences in their nature, to take up the north shore separately from the east, west, and south shores. Nowhere else about the harbor does the Spartina association assume such prominence as along the south side of the Spit, which stretches across the north end of the Inner Harbor. We may therefore legitimately regard this as the highest development of the Spartina association and discuss in this connection not merely the distribution of the Spartina in this particular area, but also the general vegetative and reproductive characters always shown by this grass wherever found. The area occupied by Spartina on the Spit is greater than the sum of all the other Spartina areas of the harbor. Starting at the northwest corner of the harbor, we find that there is a pocket in the shore about 200 feet in diameter quite filled with Spartina, except for a few tide-pools and a fresh-water stream from a ram. From this region east- ward to 200 east the border of Spartina is 50 to 100 feet wide (plate vir 4). It then suddenly broadens out until, from 500 to 900 east, the Spartina stretches out 600 or 800 feet southward from the shore of the Spit proper (plate 1). This broad band of 8. glabra along the eastern third of the Spit serves, we shall see, as a protecting barrier of great importance to the plants of the upper levels of the beach, above 6.5 feet. From 800 west to 200 east the lowermost stands of Spartina are on bottom at from 2 feet to 2.5 or 3 feet above mean low water. Eastward from here the lowest or southernmost boundary of the Spartina corresponds pretty closely with the 1.5-foot tide-line or contour, as it does elsewhere about the harbor (see plate 1). It is noteworthy that though the lower border of this marsh is very irregular as far as 600 east, from there eastward and northward it is quite regular. This latter fact is probably related in some way to the presence of the ‘strong tidal-currents through the Inlet. We shall have occasion to recur to this later. The level of the soil bearing most of the Spartina for 30 or 40 feet inward from this southern margin of the Marsh lies between the 2 and 3 foot levels. The upper limit of Spartina throughout this band is near the 6.5-foot level (plate x). Only in a few places does it fall to, or slightly below, the 6-foot level, as on hard gravel or on shifting sandy bottom at 2,800 north by 900 east. In the northwest corner of the harbor, 900 to 1,000 west, rather thickly scattered Spartina may grow as high up as the 7.5-foot tide-line, though the dense, pure stand ends here as elsewhere at about 6.5 feet. The cause for a local rise in the upper limit at this point is perhaps to be found in the extreme flatness of the shore here, which causes poor drainage, such as we shall find on the marsh at the south end of the harbor. Possibly the wet soil here is due to the presence of fresh water in the subsoil, though no adequate evidence of this has been found. We do not find here Scirpus americanus or S. robustus, which are commonly found in soil containing fresh water at these levels. The substratum upon which most of the Spartina glabra of this south shore of the Spit is growing is a more or less firm, peat-like muck. At the eastern end of the Spit, at both upper and lower limits, Spartina is found on a sandy bottom. The muck referred to may, at the upper end of the Spartina belt, be but a few centimeters in depth, while at the middle or lower portion of this belt there may be 0.5 meter or more of this muck, overlying the hard sand +{OFT. ‘ A GRAVEL Ve SPARTINA GLABRA ASSOCIATION 39 or gravel. For example, a series of soundings through the mud of the bottom, at different levels, along the main north-and-south axis, beginning at 2,700 north, showed the following thicknesses of soft mud above the hard bottom: at the 6.5-foot level 5 cm. of mud; at the 6-foot level, 15 cm.; at the 5-foot level, 38 cm.; at the 4.5-foot level, 40 cm.; at the 4-foot level, 43 cm.; at the 3-foot level, 70 cm. ; at 2.5-foot level, 66 cm.; at the 2-foot level, 36 cm.; finally, at the 1-foot level there was a thickness of but 30 cm. of mud above the firm subsoil. The thickness of the Spartina-bearing mud can be seen in the cross- section of this part of the shore of the harbor shown in figure 1. The rhizomes of the Spartina branch freely and run along more or less horizontally at about 1 to 1.5 dm. below the surface of the mud. The rhizomes are about 7 to 9 mm. in diameter and the living portion is about 2 or 3 dm. long. It consists of several or of many internodes, and may branch several times in its length. The terminal bud of the main axis maintains its horizontal position, while the lateral offshoots turn upward and give rise to the aerial shoots. From the base of each of these shoots a new rhizome puts out, in the sea- son after the leafy shoot is unfolded. By the network of interwoven rhizomes { AMMOPHILA OISTICHLIS | CAKILE SPART. PATENS | 74 LIMONIUM SALICORNIA j | |SALSOLA SUAEDA A SOLIDAGO i ENTERO MORPHA\ 7 : Spi ala ri D spaRTINA GLABRA ee eee ae cha Os a AND ALGAE 7, 0h ft \ ¥ x. / ye TIDE STREAM, gp EN ’ ' ~ Fic. 1.—North to south vertical section, at 0 east, of the Spit and adjoining portion of bottom, showing the depth of peat or mud overlying the gravel substratum, and the more important plants that dominate each level. Horizontal scale 1 = 3,000. Vertical scale 1 = 300. thus formed, which is in some places 4 or 5 layers thick, and by the roots which penetrate to still greater depths, the soft mud is firmly bound together for 2 or 3 dm. below the surface. The aerial shoots push up above this substratum in the summer to a height varying from 1 to 2 meters, and sometimes have a diameter of 1.5 or 2 cm. at the base. In the denser stands of this grass there may be from 300 to 600 stalks per square meter. Hach aerial shoot may bear 1 or rarely 2 bladeless leaves at its base and 6 to 12 complete leaves toward the top. The size and general vigor of the plants differ greatly with the level of the soil in which they are rooted, and is usually greatest on bottom between the 3-foot and 6-foot levels. For example, Spartina growing on mud between the 3 and 3.5 foot levels, near 2,200 north by 600 east, is 15 to 20 dm. high, while other plants nearby, on soil at the 1.5 or 2 foot levels, reach only 8 or 10 dm. in height. The flowers of some of the Spartina plants begin to open in the latter half of July, nearly 3 months after the shoots push up from the stubble in late April, but it is only the more vigorous plants, e. g., those on bottom between the 3 and 6 foot levels, that begin to bloom as early as this. The smaller plants at lower and 40 THE RELATION OF PLANTS TO TIDE-LEVELS higher levels do not begin to bloom until much later than this, often in late August or even in early September. Apparently seeds are set rather freely on the stronger plants and a considerable crop of seedlings might be expected. As a matter of fact, seedlings are not very abundant, because, it seems, wnoc- cupied soil of the proper character and at the proper levels is not frequent. The seedlings that have been found in midsummer were growing on bottom just above the 1.5-foot level, that had evidently been disturbed by clam diggers (100 north by 475 east), or by water-currents (2,000 north by 1,100 east and at mouths of Creek and rivulets), just at the time that the seeds were being dispersed by the water. This stirring of the bottom formed pits and furrows in which the seeds were readily buried.* Seedlings found at the first station mentioned, on July 1, 1911, presumably from seeds ripened in 1910, were from 1 to 2 dm. high, had leaves, and a well-developed root-system, though the glumes were still attached. Our search for seedlings more than a year old was unsuccessful. All medium- sized plants examined proved to be young shoots at the tips of long runners from mature rhizomes. It is evident that the usual means of propagation and spreading to con- tiguous areas is by the longer branches of the rhizome. In this way the borders of a clump of Spartina may be spread 4 or 5 dm. in a year, but it probably takes several years to produce, on such an added area, a dense stand, such as was mentioned above, of 300 to 600 stalks to the square meter. Another means of spreading to more distant parts of the harbor is through transporta- tion of whole tufts or mats of rhizomes by the ice. The stubble, which is tough in early winter, may apparently be frozen in blocks of ice at low tide, and when these blocks float up with the rising tide whole clumps of Spartina, with 2 or 3 dm. thickness of mud tangled among its rhizomes, may be lifted and carried to other parts of the harbor. It is only when these clumps happen to be dropped on bottom at or above the 1.5-foot level that they persist for more than one season. It might be assumed that clumps lodging below the 1.5-foot level dis- appear in winter through the agency of ice, but, as a matter of fact, they do not thrive even for one growing season. Dead clumps of turf are often seen on the bottom, showing where living turfs have been dropped. Harly each summer one or more considerable clumps of the grass are found growing in new loca- tions, sometimes near the very middle of the harbor. The death of this grass at levels below 1 foot or even 1.5 feet is probably due to its inability to withstand so long a submergence as it is there subjected to. Experimental work is under way by which we hope to determine whether this is the real explanation. A very interesting feature of the distribution of 9. glabra at its lower limit is the suddenness with which it ceases to spread downward over the bottom when the 1.5-foot level is reached (plate 1114). The soil may be quite densely covered with Spartina even at the lower limit of its distribution, and the presence of its rhizomes gives the bottom sufficient firmness to enable it to support the weight of a person walking over it. The bottom just beyond that bearing Spartina drops abruptly to a level 6 or 8 inches lower. This lower bottom is usually very soft for a depth of several decimeters. About tide-pools and the little inlets making into the mid-littoral marsh, near 2,500 north by 200 east, we find this same sudden drop to lower and softer bottom. It is difficult to see why the * Once only (at 100 north by 1,000 east) were seedlings of S. glabra found growing in the peaty mud among the parent plants near the 6-foot level. PLATE (V; 1000 E IOOOE 600 400 200 W. MAP OF SYMBOLS (BESIDES THOSE USED IN TABLE F) N ls H E S By db Ao = Asparagus officinalis | Sy = Digitaria (serotina, COLD SPRING HARBOR er agit u= Elymus virginicus hf Candee LONG ISLAND, N.Y Se alae la 8 rani 100s eae y aa Se = Triplasis purpurea SHOWING DISTRIBUTION OF PLANTS GROWING VB = Verbascum Blattaria : 6 y ~ ’ | Ur ; : : Z IS M4 y 4277/3 ON THE SPIT IN AUGUST 1913. OEE INE Seah pe” ae NG IP 0s oe one Q = Atripler arenaria GTAP PTL 4 OF. 7 LE LOG oe LAPoPO KS i By Haran H. Yorx = Atr?, CHE, S4,0n77 S85 SH AONI9 4 = 5 O = Atriplex patula hastata 24) 1 as =M ictUlata CO pe 2800N}-—— desea page Pe 2800 N ® = Salicornia ambigua Scale 1:1000 Obra Orsos ; ac ) 50 100 150 200 250Feet $= Spartene patens Le COGS OO: HEX: Sioa HS Se Pekan . ; ALLO CSPI IRL? Sg as aR ee | we ge hi ee ; : re . My : i svt, thw A ES , aa ek slardadbtiaand aah tea \" af _ " ah %, per’ 't ‘ \ yeh ek et ‘) +4, ip Aw, eet! ar) i ; orn in Msn ¢ may i apne tie BATS ote vs ae i : Loe)" eee ee ree 4 oe ee Me ea) See Ae! Le nis ilies we. € haan ‘ oe stat is, See vie) str | A ae « we agar Tee | AR ae pe Aye UtiRY abhi Meiat qia’y & raed . bee i i he Vig s tebe OF t , es en Ll, Uy vit ' Soak f Paver: SOA Wile ee Fey Fs see; q 6% wie Pies aim Re Yat: MAGA Qnty ap af rary. bie Rim A Otago RRS NE S. ac eh ‘ci pO ETE 7% abe my Se ee? 1 och vk aia PARSLEY RLEERS sit oles (EEK opel po rah ura est eye del ey aimee tes | a eae f ? 4 hax a we Cen eeee Seo 9) te sae i) 4 eindading oy ey he ‘ies to ais ons 4 \ Ae " el pleats ; “ae Sty re as Tee os AS PIP Os. of wre es ¥ pene 4. ee mera Beata oh: pene Ho CR ag Ure atin ih es ‘ yy - * ace rvite Hite ila aN a intitleg i : n'y stat eNMRgtet te? wot” panel | 7 re: ‘alte yi ae in sD HA e's a 4 ~ 7 ae i, Area, ip -] 10. 11. 12. 13. 14. 15. . Gerardia maritima EXPLANATION OF PLATE XI. COMPOSITION OF VEGETATION IN THE NUMBERED AREAS ON THE MAP OF THE AWSTUARIAL MARSH, Vegetation. Atriplex patula hastata. Iva oraria. Scirpus americanus. Solidago sempervirens. Spartina glabra alternifolia. Plantago maritima (equally scattered). Triglochin maritima (dominant). . Gerardia maritima (dominant). Limonium carolinianum (3 plants). Spartina glabra alternifolia (2 doz.). . Aster subulatus (dominant). Atriplex arenaria Pluchea camphorata Spartina glabra alternifolia Limonium carolinianum. Solidago sempervirens. Spergularia marina. (equally inter- spersed). . Aster subulatus (dominant). Agrostis alba Spergularia marina \ (common). Atriplex patula hastata Plantago decipiens } (few). Solidago sempervirens . Agrostis alba (dominant). Aster subulatus (abundant). Atriplex patula hastata (common). Cyperus filiculmis (scattered). Solidago sempervirens (common). Spergularia marina (scattered). . Aster subulatus (dominant). Plantago decipiens Solidago sempervirens Spartina glabra alternifolia hye 21) Spartina patens 6. : Aster subulatus (abundant). Atriplex patula hastata Salicornia europea Scirpus robustus Solidago sempervirens Scirpus americanus. Spartina glabra alternifiora. Spartina patens. Agrostis alba ? (see fig. 21). Aster nove belgii (few). Atriplex patula hastata. Solidago sempervirens (abundant). Spartina glabra alternifolia. Spartina patens (dominant). Aster subulatus (few) (see fig. 21). Atriplex patula hastata (common). Solidago sempervirens (few). Spartina glabra alternifolia (common). Spartina patens (dominant). Atriplex patula hastata Limonium carvintanum | (common). Salicornia europea Scirpus nanus (abundant). Spartina patens (common). Spergularia marina (dominant). } (common). (common). Area. 10. We 18. 19. 20. 21. 23. 25. Vegetation. Aster subulatus (common). Aster tenuifolius. Atriplex patula hastata (common). Limonium carolinianum. Spartina patens (common). Spergularia marina (dominant). Scirpus nanus. Spergularia marina. Agrostis alba (dominant). Juncus Gerardi (common). Solidago sempervirens. Agropyron repens. Ambrosia artemisiifolia (common). Cuscuta sp. Distichlis spicata. Plantago major. Polygonum sp. Solidago sempervirens (dominant). Aster subulatus (abundant). Cyperus filiculmis. Scirpus robustus (abundant). Spartina glabra alternifolia (abundant near stream). Spartina patens. Scirpus. ericar ‘p america Paonen i 1 Spartina glabra dominant). alternifolia . Althusa cynapium. Ambrosia artemisiifolia. Aster subulatus. Atriplex patula hastata. Distichlis spicata (codominant). Plantago major. Scirpus americanus (codominant). Solidago sempervirens. Spartina glabra alternifolia. Spartina patens. General mixture of— Agropyron repens. Aster nove belgii. Carex silicea. Erechtites hieracifolia. Holcus lanatus. Juncus Gerardi. Lycopus virginicus. Polygonum hastatum. Ptilimnium capillaceum. Scirpus americanus. Scirpus robustus. Solidago sempervirens. A recently denuded spot: Aster subulatus (dense stand). Spartina glabra alternifolia (400 stalks). . A denuded area: Aster subulatus. . Gerardia maritima (abundant). . Pluchea camphorata (dense stand). JOHNSON AND YORK. PLATE XI, OF I200E 200% 200 N (Gays = “ = PUA 2 ge awTITLii tt Ef gvo4 2008 JOHNSON AND YORK. PLATE XI, an HOE G00 E 800 2001" . 1200 E 200 N ay ec 22 SS ne OS Ne O-N.&S. KOS =< = 0 . ‘i o u te LLP 5 ae fo ff / MLA OW: eee Vis ie fe Vy oe SS AN x SS i 7 ee 0 eo = Ay p> SS ATEN OS a Xo Z SS > XX \ ARUN ? oe SSS S \ aS Z SYMBOLS Ney f ‘ a iy Us (BESIDES THOSE GIVEN IN TABLE F) Pear note) WAS COL fy Aulus oN i HH = Agropyron repens — TS, Oi Sige VIN ENN [|||] = Aspidzum thelypteris Ly on ® = Aster swbulatus IS a = Atriplex patula hastata gris — =Distichlis spicata vibe r3e% = Eleocharis olivacea i SY = Juncus Gerardi “fo, = SCirpus americanus 288 = Scirpus robustus YY = Spartina glabra alterniflora Yi; = Spartina patens _ 9 | ® = Solidago sempervirens. tpi Tp =Tide pool 50> Au =Aster subulatus 400E 600 E lOOOE I200E DISTRIBUTION OF THE CoRMOPHYTIC VEGETATION or AESTUARTAL MArsn, Cop Sprina Harpor, in 19138. By Hartan H. York ; . sAl “ EC Scale fe) 50 100 150 200 250 Feet SEED PLANTS OF UPPER LITTORAL BELT 717 The soil on which S. patens grows at the west end of the Spit is, at its lower margin, a compact, peat-like, saturated mud, having a depth of from 14 to 24 inches. At the upper margin the soil bearing the sparser stand of S. patens becomes drier, more sandy, and much thinner, often only 6 or 8 inches deep between the 7.5 and 8 foot levels. Spartina patens on the steeper shores of the harbor: The short, narrow strips of S. patens found about the harbor are few and scattered on the east and west sides, but more numerous on the eastern half of the Spit. On the east side, for example, there are small patches of the grass on the wharf at 950 north, and still smaller ones, in which some 8S. glabra is found, on the elevated areas between the fresh-water streamlets on the east side of the Marsh, between 0 and 200 north (see plates x1 and x111). More considerable areas of nearly pure S. patens are found on the projecting points of the shore at 200 north and 300 north. On the west shore there are short strips of this grass at 790 to 930 north and at 1,010 to 1,040 north; a broad strip at 1,650 to 1,725 north; a short, narrow strip on elevated soil completely surrounded by S. glabra, at 1,750 to 1,765 north. Beyond this are found but two very small patches at 1,825 north and 2,000 north (plate x111). The only stands of the grass on these two shores are at the points mentioned. On the south shore of the Spit, as we have intimated above, the continuous band of Spartina patens found in the northwest corner of the harbor does not reach eastward beyond 590 west. East of this we find S. patens in isolated strips from 10 to 100 feet long. These strips of nearly pure S. patens may occupy the whole width of the upper littoral beach between the S. glabra and the 7.5-foot level, e. g., at 280 to 390 east, 530 to 560 east, 675 to 730 east, and at 830 east. At other points, however (plate virB), the 8S. Patens may form rather narrow and short patches of pure S. patens, very nearly surrounded by the Sueda or Salicornia europea, which at these places form the dominant plants in the cover- ing of the upper httoral beach, e. g., at 250 west and at 430 to 450 west. At still other points the Spartina may occur scattered rather evenly through the dom1- nant Sueda or Salicorma europea, e. g., at 370 to 480 west and at 390 to 530 — east. (See plate v.) The conditions affecting the distribution of S. patens are suggested by what we have said above of that distribution. It is evident that this grass can grow on either peat or mud, or even on sandy soil, between the 6 and 8 foot levels, if the soil is not flooded by salt water longer than 5 or 6 hours per day, and is not saturated by fresh water. How far each of these various factors works directly and how far indirectly has not been determined definitely in the only way it can be, namely, by experiment. It seems probable, however, from a study of the occurrence of this plant and its competitors, that it does not dominate on soils saturated by fresh water because it does not endure fresh water as well as its competitors, and therefore is driven out by them. That it will endure some fresh water in and above the soil seems evident from the fact that S. patens is found beside the fresh-water streamlets on the east side of the Marsh. The lower limit of S. patens is probably determined chiefly by the competi- tion of S. glabra, since in a few places where the latter is absent the S. patens goes down to the 6-foot level, and at 200 north on the east shore to the 5.5-foot level. Practically everywhere about the harbor S. glabra occupies the next lower belt, and it is evidently the unfavorable physical conditions for this latter 718 THE RELATION OF PLANTS TO TIDE-LEVELS erass that keep it down to 6.5 feet and so determine the lower limit to which Spartina patens usually reaches. The upper limit of S. patens is probably determined by the physical character and salt-water content of the soil, both directly and by the competitors favored or excluded by these conditions. The lateral boundaries of the patches of Spartvna on the shore seem to be determined by the local characters of the soil. Thus, for example, gravelly sections of this upper littoral beach are pretty sure to be destitute of this grass, which is there replaced by Salicornia, Sueda, or Atriplex. Of course, it is possible that the coarser soil may be such in consequence of the lack of the Spartina as a binder. Wherever a fresh-water rivulet trickles across the upper littoral beach the band of 8. patens is broken and Scirpus americanus pushes in to occupy the soil saturated with fresh water. Even Spartina glabra may, in these moist places, push above its usual upper limit, on knobs of peat that are high enough to avoid being constantly wet with the fresh water at low tide. Juncus Gerardi: In the upper littoral belt this rush is found in dense turfs over very considerable areas of the Marsh (plate xx a), chiefly between the ?-foot and 8-foot levels, though sometimes higher, as will be seen from the work of Professor Conard (plates x1, xx1, and xx11). Elsewhere about the harbor only two patches of it are found, and these are small in area and the shoots of Juncus are intermingled with those of other species, oftenest with those of Spartina patens. In one of these areas (200 north by 1,060 east at 7.5 to 8.25 feet), the patch of Juncus is 0.5 meter wide and 4 meters long. There is here a sparse admixture of Solidago sempervirens and Scirpus americanus. On the west shore (1,700 north at the 8-foot level) there is a dense turf of this Juncus, of 2 square meters area, the only one on the whole west side. On the Spit this rush has not been seen at all. The distribution of this Juncus can evidently be studied best on the Marsh and will therefore be left for Professor Conard to discuss. We may simply remark at this point that the deep, peaty soil inhabited by this species is practi- - cally wanting, except on the Marsh. (See plates x1, xx1, and xxu1, and fig. 3, p. 111.) It is also interesting to note that at the one point on the west side where this rush occurs it is accompanied by the two plants usually associated with it on the Marsh, Distichlis and Spartina patens. The soil on which these three species here find congenial conditions is a deep, peaty muck like that of the Marsh, which is formed chiefiy by the sedimentary deposits from the very con- siderable stream that enters this side of the harbor at 1,650 north. Sueda maritvma in the upper littoral belt: This low, glaucous annual is distributed abundantly along the south shore of the Spit (plates Iv 4, v, viz B, and xiv), and occurs in rather frequent smaller patches on well-drained portions of the Marsh, but is rarely found on the east or west sides. On the Spit Sueda is distributed pretty generally from end to end, chiefly between the 6.5 and 7.5 foot levels, though it occasionally gets down to the 6.25 or up to 8 foot levels. In some stretches of the upper littoral beach it is the dominant species in the belt immediately above the Spartina glabra. On other parts of this beach Sueda may be crowded downward into the S. glabra or upward toward the 8-foot level, — or occasionally be crowded out altogether, by such competitors as Spartina patens, Salicornia europea, or Distichlis spicata, which are the other species that may become dominant in this belt. In still other portions of this belt Sueda may occur as a mere sprinkling over areas dominated by one of the three species SEED PLANTS OF UPPER LITTORAL BELT 19 just mentioned, e. g., on the Spit from 480 to 590 west. Of course, the distribu- tion of an annual species like this may differ somewhat from year to year, but not very widely, since seedlings each year can find suitable space only in the areas occupied in the preceding year by their parents or by their, likewise annual, competitor, Salicornia europea. The only chance Sueda has of invading the more considerable area occupied by its perennial competitors, Spartina patens, Distichlis, and Salicornia ambigua, is when these are smothered out by flood-trash, or uprooted by fishermen digging on the beach. Such free soil is usually promptly appropriated by either Sueda or the annual species of Sal- cornia. In those areas on the Spit where Sueda is the dominant species (e. g., 780 to 820 east, 20 east to 380 west and 480 to 590 west), the band of this plant may be from 8 to 12 feet wide. In these stretches the Sueda may be 2 or 3 dm. high and stand as thickly as 100 to 200 plants per square meter. In such areas there may be only 2 or 3 plants per meter of Atriplex arenaria or Limonium, or 5 to 10 plants of Saltcorna europea, to dispute its dominance. From 20 east to 200 east at 6.5 to 7 feet it nearly equals in quantity the barely dominant Salicornia europea, while between 7 and 8 feet it becomes much sparser than the latter (plates x111 and xiv). In other areas, e. g., from 20 to 270 east, we find a dozen or two plants of Sueda per square meter, scattered through the dominant Salicornia europea or S. ambigua. Even in this strip there are short stretches where the Sueda is entirely crowded out by these competitors, except at the very upper and lower edges of the upper littoral belt. ‘Toward the west end of the Spit (800 to 1,000 west), Sueda, often to the number of 8 or 10 plants per square meter, is scattered, along with occasional plants of Salicorma europea, LIimonium, and Atriplex patula, through the dominant Spartina Patens. Sueda on the Marsh: On the Marsh south of the harbor Sueda is found most abundantly on the better-drained parts, such as the edges of ditches or along the tide-streams (e. g., 20 north to 30 south by 950 east and 100 south by 1,090 east). Nowhere on the Marsh, however, does Sueda attain the maximum size or density of stand found on the Spit. ~ On the west shore Sueda has not been seen at all, and on the east side it has been found only on the stone pier at 950 north, where it is usually scarce. From the examples cited above, which illustrate the more typical areas that have been occupied by Sueda during the time our work has been in progress, it will be seen that it may grow under the following conditions: It is found on well- drained, peaty soil (e. g., on the Marsh), or on relatively thin layers of fine- grained mud overlying sand or gravel (e. g., at the upper edge of the Spartina glabra on the Spit). Its densest stands, however, are found on the higher levels of the upper littoral beach, where the soil is a pretty clear sand or fine gravel. Those parts of this beach on the Spit where Sueda occurs over its whole width have a sandy or gravelly soil down to the very edge of the Spartina glabra. Sueda always grows in well-lighted areas, with no more shade than that fur- nished by the small, scattered plants of the Spartina glabra at the upper edge of its belt. Sueda is not found at any station about the harbor where fresh water is present in the soil, or covers the soil, or surrounds the shoot of the plant at any stage of the tide. There is no experimental evidence to show what amount of exposure to salt water and to air Sueda will endure. The fact that it occurs 6 80 THE RELATION OF PLANTS TO TIDE-LEVELS at the 6.5-foot and in a few cases at the 6-foot level shows that it can withstand a submergence of 3 to 3.5 hours per tide, or 6 or 7 hours per day. Its occurrence at the 7.5 foot and, more rarely even at the 8.25-foot level, where the shoot may not be submerged for several days together, shows likewise that frequent sub- mergence of the shoot is not necessary, even in regions with a rather dry atmos- phere, like the Spit. The plants of Sueda are, however, rarely so high on the beach that their roots can not reach to a soil that at least part of the time is saturated with salt water. It is to be recalled here that, as one can see on any calm day on the beach, the tide-water is carried up several inches above high-tide level by capillarity. This means that the water goes considerably higher in the soil than the 7 or 7.5-foot level at high water of a neap tide. That this level of the soil-water is a factor of some importance to the Suceda is indicated by the fact that, e. g., at 800 to 900 east on the Spit, this species stops near the 8-foot line, leaving a beach above this that is quite bare of vegetation. In this place there are no discoverable differences in the soil above and below the 8-foot level, and there are no plant competitors above this contour. It seems probable, there- fore, that the lack of sufficient soil-water may be the condition excluding Sueda from the upper levels of this shore. Unfortunately no actual determinations of the water-level or of the salt-content of the soil-water have as yet been made at this point. On some parts of the upper littoral beach, as has been noted above, the Sueda is displaced from levels between 6.5 and 7.5 feet by Distichlis or Salicornia europea. Whether the competition between these plants is such that some slight local difference in the character of the soil may give one or the other of these two species the advantage over the Sueda is uncertain. It is possible that the greater amount of humus usually present in the soils occupied by these two competitors may allow them to become established in these areas, while in the more purely sandy soil Sueda is the successful competitor. Salicornia europea in the upper littoral belt: This plant is found abun- dantly on the Spit, often in dense stands for from 5 to 20 meters along the shore. It is widely but sparsely scattered over certain parts of the Marsh also, while it is wanting from the other two sides of the harbor, except for two points on the eastern shore. (See plates v, XA, XIII, and XIV.) On the south shore of the Spit this species of Salicorma reaches its maximum development in size and abundance as well as in purity and density of stand. At the western end of the Spit (980 to 1,000 west), this Salicornia was found scattered thickly through a belt of dwarfish Spartina glabra some 4 or 5 meters wide, near the upper border of the latter. Near the 7-foot level Salicornia is mingled with Spartina patens, also with some Distichlis and Sueda, while at the 7.5-foot level Salicornia becomes completely dominant. Farther eastward the sprinkling of Salicornia becomes more copious, e. g., though this upper littoral belt from 480 to 590 west was dominated by Sueda, there was an admix- ture of nearly as many plants of the Salicornia. Between 380 and 480 west this belt is dominated by Salicornia europea, except for an occasional narrow bar of Spartina patens cutting across it. Between 200 and 380 west this — Salicornia is usually very sparsely represented, but from 200 west to 20 east it is, in most years, exceeded in numbers only by Sweda. Eastward from the latter point Salicornia dominates this upper littoral beach as far as 280 east, though often mixed with abundant Sueda. Next follows a stretch dominated by —_— JOHNSON AND YORK. j;o0d0 W. - 800 2600 JO HNSON AND YORK. PLATE Xlt, ee 800 600 400 200 w. 0 200 E. 400 600 800 1000 1200 1400 E. 3000 H Pia 3000 N. 2800 2000 1800 1600 1400 1200 b neseqno\ \ SS LABORATORY wy 1000 1000 800 T 800 600 if | 600 N 400 silt 400 Beye 200N. ero. 4 oat Scale 1.4000 else \ Fe 4 0 100-200-300 400 SOO FEET _| well ew WS a ean ‘ 0 ELEVATIONS AND DEPTHS IN FEET [Lise lines (even feet) 200 Tide lines (odd feet) 700 ere | x |Location of range stake Se i 400 | | STATION FOR \ 400 EXPERIMENTAL Lower limit of Spartina glabra EVOLUTION Penn Limits of Zostera marina 600 S. 600 S, x —l 4 1000 W. 800 600 400 200 W. 0 200E 400 600 800 1000 1200 1400 E. Map or InnER Harpor, CoLtp Spring Harsor, Lone Istanp, New Yorx. By Duncan 8S. Jonnson AND HArian H. Yor, This map shows the distribution of the vascular plants, found between tide marks, that are associated with fresh water, i. e. that grow in soil of which the soil water is made practically tresh by the proximity of rivulets or seeping fresh water. The plants in question are: Aspidium, Hibiscus, Impatiens, Iris, Lilaeopsis, Sambucus, Scirpus americanus and S. robustus. The symbols (printed in green) tised to indicate the position of specimens, or groups, of these plants are those given in table F. f . A ¥ j ; } } Pe WE ; ie Z 4) i y > - 7] vail 4 ay : 21) TOG @ d_ariep ee Te ae, we at ai Ban tia | : I : y = er nes ld ; Citgo ARY . i ca! 7% a eb « SOF Hie = , “ubia ss “ i eonewed 9 ; wh Ehiee bo hs -) : ' Low Woe * ay ; ” , iy ; ao? Way F 4 ’ wv a a : i Pl! 2 Poles. coe ~iele 4, I’ @ A = at "fe 9 " ’ ( ¢ y : BD J ~~ mr Lo « >» deel ay ~ oie OFTHE wS % yey my ? Tt? VATTVERSITY DF ot . ba) ? " V4 . | ‘ iv } ii i ) ei “ty a meitle = f , ' a - 7 6,97 4 e . 6 i \! Pee g) * “4 . y i ' = some ¢ , : i ait i i ™ i oad io “ - j J | = 4 § i =) " } 7 mrt JOHNSON AND YORK. 1000 W. 800 600 400 3000 N. PLATE XIII, 200 W. 0 GLOOM SY, 14-00 E. are N. 2400 2200 2800 —+—42600 +—424.00 2200 | 2000 2000 1800 1600 See 1800 Slime LOO 1400 1400 =i 1200 iP 1200 1000 800 600 400 20on, 600 1000 800 600 400 200N. eon. 4 Scale 1:4000 on & 9 100 200 300 400 SOOFEET | weccrw “Ae! sae ees 540) oe PLA Aas na ; ELEVATIONS AND DEPTHS IN FEET |} —~|Tide lines (even feet) zoos} [J Tide lines (odd feet) eke 2005. from] Whart line | x tion of range stake wei AY ; c Py. 400 [x _]t0ce pe rary in aay = TIBOR i \ a f EXPERIMENTAL \ } rj] Lower limit of Spartina glabra EVOLUTION BS ee Papa] Limits of Zostera marina : Ae ene. 1000 Ww. 800 600 400 200 W. 0 200E 00 600 800 1000 1200 i400 E. Map oF InNER Harpor, CoLp Sprinc Harzsor, SHOWING THE DISTRIBUTION OF THE VASCULAR PLaNts OccurRiInG BrEtow THE 10-Foor LeveL, Nor ASSOCIATED WITH) FRESH WATER INLETS By Duncan S. Jonnson anD Harztan H. York, Sympos, PLANT INDICATED. A Ammophila At Aster tenuifolius Aa Atriplex arenaria Ao Atriplex patula B Baccharis Cc Cakile D Distichlis Eu Huphorbia polygonifolia fy Iva J Juncus Gerardi im Lathyrus L Limonium pd Plantago decipiens pr Polygonum maritimum Ry Ruppia Sm Salicornia ambigua se Salicornia europaea sd Solidago sempervirens Sp Spartina patens sj Spergularia sy Suaeda T Triglochin Z Zostera The frequency of the symbols indicates approximately the abun- dance of the species. Only the horizontal distribution along the beach can be shown with any accuracy, owing to the crowding of the symbols in many areas. The vertical distribution can be learned more exactly from the text. The general distribution of Zostera and Spartina glabra is shown in black. In the case of the former the abundance of scattered plants outside the area of greater density is indicated by the proper symbol printed in green. The distribution of these plants on the marsh is shown on Plate XI. SEED PLANTS OF UPPER LITTORAL BELT 81 Spartina patens, but from 480 east on to the east end of the Spit this belt is dominated by Salicornia europea, often mixed with numerous bushy plants of its relative, S. ambigua. In one place only (620 to 660 east), does the latter become abundant enough to really crowd out the more erectly growing S. europea. Three or four similar interruptions of the band of Salicornia europea near the eastern end of the Spit are due to short patches of Spartina patens or Distichlis. At the eastern extremity of the Spit, Sueda and Atriplex patula may be mingled with the Salicornia, while at the very tip the Salicornia is usually sprinkled thinly over an otherwise comparatively bare sand beach (plates Vv and XIII). On the Marsh Salicornia europea may in some places be sparsely distributed -and in other parts areas of several square meters may be covered to a density of 100 plants per square decimeter. Throughout the Marsh it is chiefly confined to the margins of the tide-streams, tide-pools, and artificial ditches (100 north by 1,150 east at 6.5 to 7.5 feet and 100 south by 900 east). On spots made bare by the smothering out of Spartina patens by tide-trash, Salicornia europea is often the first thing to appear when this trash is finally removed by some very high tide, e. g., at 100 north by 1,090 east in 1909. On locally elevated areas in the midst of the Spartina glabra, even down to the 6-foot level, Salicornia is sparingly mixed with such species as Aster subulatus, Atriplex patula, Limo- nium carolinianum, and Scirpus nanus, as, e. g., at 400 to 440 south by 770 east, between two streams. On the east shore of the harbor Salicornia europea is usually seen only at 200 north, between 6 and 7.5 feet, where it is only sparsely sprinkled among the Spartina glabra and the 8. patens on this rather well-drained point of the shore. In one season only (1908) were a few scores of this plant found between 7.25 and 7.75 foot levels, on the stone pier at 950 north. Nota single plant of this species could be found along the whole west shore, from the northern edge of the Marsh to the Spit, though a careful search was made for it. The factors influencing the distribution of this species may best be suggested after noting the distribution of the second species of Salicornia, which imme- - diately follows. Salicornia ambigua in the upper littoral belt: This perennial, half-ever- green species of Salicornia is confined to the eastern third of the Spit, except for a colony of 5 tufts, each 0.5 meter across, that has established itself on the north side of the stone pier on the east side, and a single plant at 1,010 north on the same shore. Mature, established plants are readily distinguished from those of S. europea, but it is possible that this species may be represented on the Marsh by seedlings or young plants which were not distinguished from those of the annual species. On the south shore of the Spit S. ambigua is chiefly confined to the region between 390 and 600 east (plate x11r), not more than a score of plants of this form being found outside these limits. Only between 620 and 660 east, however, does this Salicornia become completely dominant. Here it forms a practically pure stand, with thickly matted branches, over a strip 1.5 meters in width, between the 6.25 and 6.75 foot levels (plate xB). Along the beach from 390 to 620 east this species is mingled with or at times crowded out by S. europea, with now and then a turf of Spartina patens or Distichlis to inter- tupt the continuity of the stand of these two glassworts. Beyond 660 east the plants of 8. ambigua are either scattered singly or may be grouped in twos and 82, THE RELATION OF PLANTS TO TIDE-LEVELS threes, over a beach covered chiefly, though often sparsely, by either Sueda or Salicornia europea. There is one group of a dozen of these perennial Salicor- nias between 790 and 820 east, of which most are 6 or 8 dm. across the individual plant (plates 11 and XIII). The distribution of the two species of Salicornia: From what has been said above of the distribution of these two Salicornias, it is evident that the concur- rence, in any area, of all the conditions allowing the establishment of a dense stand of either is rather rare on the shores of this harbor. Even the thinner stands occur in but a few and relatively small areas, except on the Spit. We are unable to do more than suggest the possible factors influencing the horizontal distribution along the shore. We have been unable to discover any very probable determinant of the vertical distribution of these two plants. It seems evident that the horizonal extent of the patches of the annual S. europea, along the beach, is determined by its perennial competitors, especially by Spartina patens and Distichlis. The seedlings of this Salicornia can start only on unoccupied soil, which means either soil that has been bared of its competitors or soil that can not be successfully occupied by them, even with their advantageous habit of spreading to adjoining territory by means of their rhizomes. It will be interesting to note in this connection that in early April 1911, when the beach was still bare of vegetation after the winter, many seedlings of Salicornia, probably S. ewropea, were found on the Spit far beyond the areas that are oc- cupied by mature plants in summer. Many of them, for example, were found on the mud between the dead stumps of the Spartina glabra, down as far even as the 5-foot level. Others had started higher up, where they would be sure, later on, to be shaded out by the rapidly growing shoots of Spartina patens. Shreve, and also Chrysler (Plant Life of Maryland, p. 131 and p. 178), have suggested that Salicornia europea grows on areas where the soil-water is subject to concentration by evaporation, and that the high salinity so attained is really the factor that determines the occurrence of Salicornia on these areas. This assumption would not adequately explain the distribution of this species at Cold Spring Harbor, for here, as we have seen, it grows luxuriantly on beaches the soil of which is flushed out by a submergence of from 3 to 3.5 hours each tide. Moreover, S. ewrope@a grows on the point between two streams, at 440 south by 770 east, just above the 6-foot level, where it must be overflowed by fresh water for at least 3 or 4 hours daily. As the tide rises the fresh water of the two streams is backed up north of the causeway, and it is not until the tide has risen to at least a foot above the substratum that the layer of fresh water next the substratum is replaced by salt water. Salinity tests made at this point show specific gravities of soil water of from 1.015 to 1.017. It is to be remarked, however, that Salicornia has never been found growing where fresh water is constantly present in the soil or flowing over it at low tide. The Salicornias, at least S. europea, grow on either muddy, sandy, or gravelly soil, though the denser stands of both species are found on the gravel. All soils bearing either Salicornia have at least moderately good drainage, for example, _ when growing near tide-pools it is always on the more elevated parts of their margins, above the constant water-level. Salicornia is found in well-lighted areas, in the open sunlight, except for the little shade given it in some places by the neighboring Spartina glabra. Neither Salicornia has been seen on the west side, where the conditions are apparently otherwise favorable, but where, as we have seen, these levels of the beach are deeply shaded for half the day. SEED PLANTS OF UPPER LITTORAL BELT 83 The seedlings of Salicornia europea are very numerous in the spring. In July each year plants of all sizes are found, from seedlings of 2 or 3 cm. up to mature plants. This indicates a marked difference either in time of germina- tion or in rate of development, for no seeds have as yet been shed even from the oldest plants of the season. The perennial 8. ambigua does not appear to spread by the rooting of its decumbent branches, and probably does so by its seeds, though its seedlings were not distinguished from those of S. europea. The vertical range of distribution of Salicornia europea is from 6.5 to 7.25 feet, but small plants of it have been found as low as 5.5 feet (200 north by 1,020 east), and rarely it goes up to 7.75 feet (2,860 north by 500 east and 100 south by 900 east). Salicornia ambigua is found only between the 6.5 and 7 foot levels on the Spit, but may be capable of ranging much more widely where conditions encourage a more abundant growth. As a general conclusion from all observations made on these Salicornias, it may be suggested that the vertical distribution of these plants is determined primarily by physical conditions, of which the chief are the time of submergence of the shoot at its lower limit and the low percentage of soil-water at its upper limit. The horizontal distribution is directly influenced somewhat by soil characters, but is apparently determined ultimately, in the case of S. europea at least, by the power of its perennial competitors to hold their own against the seedlings of the Salicornia. Between the two species themselves there is evidently keen competition. Scirpus americanus in the upper litoral belt: This plant, which is a dark- green, few-leafed rush with triangular culms, about 0.5 cm. thick, and from 0.5 to 1 meter high, is widely scattered about the harbor in this belt, except on the Spit (plate x11). Along most of the east and west shores where this rush occurs at all it is sprinkled in with Spartina glabra near the upper border of the latter (plate 1vB). Higher up there is still but a sprinkling among the suc- cessors of the Spartina, such as Spartina patens (e. g., 1,000 to 1,020 north by 1,050 east). In still other places, though the stalks of the Scirpus may be thinly scattered, the soil between them may be destitute of other plants and perhaps covered with a layer of tide-trash beneath which this plant seems to persist more - readily than other species. There are but few places along the west shore where this Scirpus is abundant enough to dominate the upper littoral belt (e. g., between 640 and 800 north, 900 and 1,000 north, 1,850 and 1,900 north). Only on the southern end of the Marsh at the head of the harbor (350 to 500 south by 1,000 to 1,150 east) do we find this species really dominant over any consider- able area (plates XV B, XIX B, and xx A). LHven here it seldom occurs in as pure a stand as that formed by Spartina glabra, 8. patens, or even by Sueda and the Salicornias on the Spit. The soil occupied chiefly by Scirpus is usually firmly bound by its rhizomes, which run about horizontally about 10 to 15 cm. below the surface. In the denser stands there are 10 to 15 culms per square decimeter. The soil bearing Scirpus americanus is peat or mud, chiefly between the 6 and 8 foot levels. Sometimes, near the larger rivulets, it gets down to the 5-foot level on lumps of peaty mud which are surrounded by fresh water for 4 or 5 hours at each low tide (1,250 north, on the west shore). It does not grow on the gravelly areas from which this peaty top-soil has been eroded by these streamlets. On the other hand, this rush may grow at considerably higher levels than the upper limit mentioned above. This is true at one or two points along the west shore (e. g., 1,700 north), and especially on the marshy area 84 THE RELATION OF PLANTS TO TIDE-LEVELS south of the harbor, where, as noted above, this species attains its best develop- ment. Here it grows densely on soil at the 8.5 or 9 foot level, and at one place it is found at 9.25 feet. On the sunny east shore at 1,000 and 1,040 north this rush forms rather dense patches near the 8-foot level, and ascends still higher near the inflowing fresh-water rivulets. In the preceding paragraph reference is made to the occurrence of this Scirpus near fresh-water streams, and to its complete absence from the Spit, which is devoid of fresh water. After studying the entire shore of the harbor, it is clear that Scurpus americanus is found only in soils where fresh water is present, either running over the surface or barely saturating the mud as the water seeps through from little springs in the underlying gravel. This latter seems to be the case, for example, on the west shore, near 800 north, 1,800 north, and 1,900 north, where, though no fresh water is found running over the beach between the 7 and 8 foot levels when the tide is out, yet the soil is constantly saturated even after many hours exposure. Moreover, the water collected in holes dug in this soil is entirely fresh to the taste and, at low tide, fresh water is also found trickling out of the beach at the 3 and 4 foot levels, directly below these Scirpus areas. On the Marsh also this Scirpus often grows in spots where no fresh water is visible on the surface. The soil-water, however, proves to be fresh when its specific gravity is taken. This is true, for example, of the large area between 400 and 500 south and 900 and 1,100 east, which is dominated by S. americanus. The soil-water here is practically fresh during the growing season, except just after the very high storm-tides mentioned above. In brief summary of the conditions under which Scirpus americanus grows, we find that it is a plant of sunny situations. It is absent from shaded soil on the west side, though this be wet. In fact, the Spartina glabra from the belt below has been found to replace this rush in such wet, shady spots (see p. 45). Scirpus grows chiefly on soil between the 6-foot and 8-foot tide levels, except on the Marsh and at one or two spots on the east side, where it may reach the 9-foot level in wet, sunny places. This gives the plants an exposure of 15 or 16 hours per day in the case of the lower ones and of 24 hours per day for the higher ones, except on the 5 or 6 days of each month when high spring or storm tides occur. The submergence varies from 3 to 10 hours per day. The critical factor determining the lower limit of this Scirpus is probably the high salt-content of the soil. It never gets far below the 7-foot level, except where fresh water is abundant enough to wash the salt out of the soil. It is, of course, possible that this fresh water really acts indirectly, by preventing the growth of its competitors in these soils (e. g., of Spartina glabra). It is conceivable, for example, that this Scirpus might occupy any soil between the 5.5 and 8 foot levels, if only its competitors are kept out. This has not as yet been experimentally proven. The upper limit of distribution is probably determined by shade, or by the lack of sufficient soil-water on some parts of the beach. Tlsewhere, on the contrary, even in wet soils, its upper mit seems fixed by the competition of other species which can not follow the Scirpus down — to levels that are flooded by salt water, but can successfully compete with it when they have not this adverse condition to meet. Scirpus robustus on the upper littoral beach: This large, more leafy rush resembles S. americanus in its distribution, but is less abundant and less widely * Tests made at a few points show that this species can grow in soil water with a specific gravity of 1.006 or even of 1.017. SEED PLANTS OF UPPER LITTORAL BELT 85 distributed (plates xt and x11). There are but four patches of it on the west side and only six on the Marsh, and it is entirely wanting from the east side, north of the Marsh, and from the Spit. This species of Scirpus is, in fact, less abundant and less widely distributed than several of the other plants of this belt to be mentioned later. It is discussed here, immediately after S. americanus, for the sake of more ready comparison with this species. S. robustus is con- fined, like its relative, to areas with fresh soil-water. It rarely forms pure stands of any considerable extent. Stands of 50 square meters are found at 1,600 north on the west side, and one near 500 south by 880 east. Nearly pure stands of smaller area are present at 590 south by 740 east and near 120 south by 1,200 east. More often it is mingled with Spartina glabra, S. patens, or Scirpus americanus; e. g., on the west shore at 1,980 to 2,020 north or on the Marsh at 550 south by 730 east. The lowest level from which this species has been recorded is 7 feet and its upper limit is at 9 or 9.25 feet. As was suggested above, this Scirpus is found only on soils supplied with fresh water. In some areas this water is evident on the surface, e. g., on the west side at 1,415 north, on the Marsh at 120 south by 1,200 east. In other places the fresh water is not at first evident, but is found on investigation to be present in the soil. A striking instance of the latter sort is the small area, between two streams at 470 south by 830 east, which is elevated 1.5 or 2 feet above the bed of these streams. ‘his area is covered with a mixture of Spartina glabra, 8. patens, Scirpus americanus, and, most prominent of all, the present species. ‘This same mixture extends eastward from the point named on soil, from 8 or 10 inches below the surface, of which a rivulet of fresh water trickles out at low tide. Not only is the soil- water fresh, but the overlying water at high tide never becomes very salt. Spe- cific-gravity tests made at this point when the tide was at the 8-foot level showed a density of but 1.005 at the surface of the soil bearing these plants. At the time of the spring tides, which in summer reach 9 feet, or of storm tides, which in summer reach 10 feet and in winter even 12 feet, all inflowing fresh water must be backed up south of the road embankment, which crosses the Creek. The whole Marsh would then be covered with from 1 to 3 feet of sea-water with a density of 1.019, like that of the harbor itself. This shows that the shoots and more superficial roots and rhizomes of this plant can endure submergence in salt water for several hours a day, even when in a growing condition. It is probable, however, that the salt water never penetrates far into the soil here, because of its compactness and of the constant supply of fresh water from below. Distichlis spicata on the upper littoral belt: This is a slender grass 4 or 5 dim. in height, with narrow, often glaucous leaves. It grows, chiefly between the 6.5 and %.5 foot tide-lines, in a number of small areas on the Spit, at a few points on the Marsh, at one point on the east side, and two on the west shore (plates v, x1, and x1v). Pure, or nearly pure, stands of Distichlis are found at a few points on the Spit (plate xx B). These are but a few meters long each, but 6 or 8 dm. wide, and all are near the 7-foot tide level (e. g., 500 east at 7.75 feet, 580 to 590 east at 6.5 to 7.5 feet, and 800 to 820 east at 6.5 to 7.5 feet). On the Marsh similar dense growths of Distichlis, over smaller areas, are found at 0 north by 940 east at the 7.25-foot level, and at 370 south by 820 east near ”.5 feet. Elsewhere about the harbor Distichlis is mingled with Spartina patens, as at several points on the Spit (950 east, 800 to 1,000 west), on the 86 THE RELATION OF PLANTS TO TIDE-LEVELS west shore (800 to 930 north, 1,600 north), on the east side on the pier (950 north), and finally on several small areas of the Marsh (e. g., 0 south by 1,200 east). In other areas where Distichlis is still dominant, there may be a large admixture of Sueda or Salicornia, or even a scattering of Atriplex arenaria (e. g., 2,700 north by 0 east, 2,850 north by 800 east). The soil on which Distichlis grows is a partially drained, peaty muck, occa- sionally mixed with sand, as, for example, at the western end of the Spit. More rarely this grass is found in comparatively fine sand, in which on the Spit (750 east) it gets up above the 8-foot level. Nowhere about this harbor was Distichlis found growing in the shade or in soil wet with fresh water. The latter fact may, of course, indicate that the fresh water is directly injurious, or perhaps we should say that the semidiurnal alternation of fresh and salt water is unendur- able. Or on the other hand, its absence from wet areas may mean that it meets other competitors, or meets some of its usual competitors at a greater disadvan- tage on wet soils. ‘This grass lives on soils of quite varied character, taking all sides of the harbor into account, which indicates that it could occupy many other areas than at present if it were not for its competitors. In fact, then, it seems clear that the chief influence determining the limits of the Distichlis in a horizontal direction along the beach is the competition of its neighbors. It is difficult to discover what external condition fixes the lower limit of Distichlis at 6.5 feet. It may be that the shoot will not endure a submergence of more than 2 or 3 hours each tide or that the rhizome can not withstand sub- mergence longer than 3 or 4 hours per tide. On the other hand, it may well be that it can not compete successfully with Spartina glabra, with which it is nearly always in contact at its lower margin. The upper limit of this grass is quite variable, but it has proven impossible to determine whether this is fixed directly by some character of the soil, such as the water-content, or by the com- peting plants there present. It is, of course, realized, as has been mentioned in other cases, that the particular conditions which limit the distribution of any species can not be determined by field observation alone, but that resort to experimental study will be necessary to do this with certainty. At the start, however, field observation must be relied on to indicate the possible factors from among which the experi- menter may hope to select the actual controlling factor or factors. The sug- gestions offered in connection with most species in this paper are not made in the belief that they are finally established as causes of the distribution found, but as suggestions likely to prove useful to the experimental investigator. The distribution of the nine other species of angiosperms found in this belt, but which seldom dominate any area above a few square decimeters in extent, may now be briefly indicated, taking them up in alphabetical order. Atriplex arenaria: This hoary-leafed annual is found very sparsely scattered on the eastern half of the Spit (plates v and xiv), on the Marsh (plates xz and XII1), and on the old pier at 950 north on the east shore. Its usual range is from the 7-foot to the 8-foot levels, though its extreme range is from 6.25 to 8.75 feet. . It occurs in rather sandy soil on the Spit, but is most frequent in the turf of Spartina patens along the edges of the tide-streams and. ditches on the Marsh. Atriplex patula hastata is, in most years, very much more abundant than A. arenaria. It is also more widely distributed about the harbor and has a greater vertical range (plates v, x1, and x11). This species has been recorded on the SEED PLANTS OF UPPER LITTORAL BELT 87 east side of the harbor at 320 north (about 10 clumps, in 1912), and at 400 to 480 north whenever fresh water is absent. The densest group about the harbor was found on the pier at 950 north by 970 east, where there were 150 plants in 1912. On the south side of the harbor this plant is usually distributed rather sparsely over most of the area of the Marsh. It grows here chiefly between the 7-foot and 8.25-foot tide-levels, is most frequently associated with Spartina patens, and is oftenest found on the better-drained soil at the edges of tide-pools, streams, or ditches. Its general frequency is that indicated on the area mapped in plate vir. On the west side this species is sparsely but widely distributed along the whole natural shore (740 north, 1,200 to 1,410 north, 1,650 to 1,750 north and 1,970 to 2,070 north). Usually it is found among Spartina patens, but it is sometimes mingled with Solidago sempervirens near the 8-foot level, and it is absent from soils saturated with fresh water. On the south side of the Spit, Atriplex patula has the same wide but sparse distribution that we have noted elsewhere. It is found scattered in the dense turfs of S. patens (800 to 1,000 west), or close to the upper margin of S. glabra (840 east at 6.5 feet). The more usual range of this Atriplex is from 6.5 to 7.5 feet, but at 400 to 480 north on the eastern shore it gets down below 6 feet, while on the well-drained shore at 320 north on the east side, it goes above 8 feet. On the west shore, near 1,800 north, and on the north shore of the Spit, between 400 east and 400 west, it is often found at 8.5 feet. Iris versicolor, while really to be regarded as a denizen of the next higher belt, may form dense clumps of vigorous, abundantly fruiting plants in the upper littoral belt, on firm soil that is protected by neighboring springs and rivulets from saturation by salt water (plates 1vB and x11). Thus, on the west shore (1,350 north, 1,400 north) Jris gets down to 8 feet or just below, while on the east shore it grows in soil at 7.5 feet, or even, at one point, at 7 feet. In the latter locality (10 north by 1,192 east) the soil-water at this level, and the sap of the Jris roots growing in it, are not at all salt to the taste. The soil, however, is covered with salt water twice daily, except during two or three neap tides of each fortnight. Jris forms a very striking example of the way in which the shoots of some inland plants can withstand immersion in salt water, if only the soil-water be fresh. The general occurrence of this species about the harbor is indicated on plate x11 and will be discussed in speaking of the vegetation of the next higher belt. Linonium carolinianum is one of the most widely distributed species of this upper littoral belt in soils free from the influence of fresh water. ‘This has often been suggested above in speaking incidentally of its occurrence in stands of other species. It is a broad-leafed, thick-rooted perennial found on all four sides of the harbor. On the east side there is a bare sprinkling of it in the better-drained spots from 20 to 450 north and from 960 to 1,150 north, while between 800 and 900 north, at 7.75 to 8 feet, there were 30 plants in 1912. Finally, on the pier at 950 north, is found the densest and most extensive stand about the harbor. There are over 300 plants around the border of this wharf, and where densest there are 20 plants per square meter. On the Marsh, Limonium occurs chiefly along the northern border between 6.5 and 7 feet, usually bordering tide-pools, tide-streams, and ditches (0 north by 880 east), and also on certain artificial, gravelly elevations (10 south by 800 east). The total number of plants on the Marsh is not over 150 or 200, 88 THE RELATION OF PLANTS TO TIDE-LEVELS and the general scattered distribution of the plant is indicated by that shown for a typical area on plate VII B. On the west shore Limonium has been found at only three points, all of which are artificially gravelly areas. A few plants are at 750 north, on a dilapidated boat-landing. About a dozen specimens were found at 1,070 north and the same number at 2,090 north. At the Spit, Zimonium is most abundant on the western quarter of the south shore (plates v, X B, XII, and xv). In the broad band of Spartina patens here between 700 and 900 north several dozens of this species are scattered, sometimes 4 or 5 ina square meter. On the eastern half of the Spit, Lamonium is scattered very sparsely; ¢. g., only 10 plants were found between 0 and 260 east. Beyond this, eastward to 840 east, the plants may be locally somewhat more abundant, but on the whole they are evenly scattered, and not more than 100 plants are present altogether on this half. The large majority of the plants of Iimonium about the whole harbor are found between the 6.75 and 7.75 foot levels. On well-drained peaty soil, such as turfs of Spartina patens, Limonium may get down to 6.5 feet, while on hard, gravelly beaches, out of reach of fresh water, it may go up to 8 or, in one instance, to 8.25 feet. It is found only in sunny situations. Plantago decipiens on the upper littoral belt: This narrow-leafed fleshy perennial is found in this belt at three or four points about the head of the harbor, on gravelly or half-drained peaty soils between the 6.25 and 8.25 foot levels (160 south by 1,090 east, 400 to 480 north by 1,040 east, and 20 south by 730 east, etc.) (plate x11). It is rather surprising that this plant has not been seen on some of the gravelly beaches of the Spit and west side of the harbor, unless it be the abundance of fresh water in the latter case and perhaps the poor drainage of the former, due to humus packed between the pebbles. Samolus has been seen at but one point in the upper littoral belt (200 north - by 1,050 east), where it grows between the 7.5 and 8.25 foot levels associated with Juncus Gerardi and Salicornia, and near its upper limit bordered by Teucrium canadense and Psedera quinquefolia. Scirpus nanus is a diminutive species that occurs in the upper littoral belt somewhat more abundantly than either of the last two species. It usually forms dense turfs, sometimes a meter or more square (122 south by 1,089 east), and grows on fine-grained peaty soils that are often bare, or nearly bare, of other vegetation, except alew such as Rhizoclonium and Vaucheria (plates xx1 and xx11). The seed plants most often found with this Scirpus, when any are present, are Salicornia europea, Distichlis, Atriplex patula, and occasionally Spartina glabra. Scirpus nanus is confined to a half dozen locations on the Marsh (e. g., 500 south by 700 east, 25 north by 1,100 east), one area on the east shore near the mill (400 to 480 north), and two areas on the west shore (660 north at 7.5 feet and 850 north at 7 feet). The soil on which this plant grows is always pretty completely saturated with salt water, the fine texture of the soil enabling it to hold the water well from one high tide to the next. At 6 south by 1,050 east, at 7.33 feet, this plant was growing well at the margin of a tide-pool, the surface of which, for the purpose of killing mosquito larvee, had been kept covered during the summer with crude petroleum. The Scirpus we are discuss- ing occurs chiefly in sunny spots, and between 6.5 and 7.5 feet, although it has been found as low as 6.25 and as high as 8 feet. PLATE XIV, oft. Btt. 2850N cog PLATE XIV, JOHNSON AND YORK. 2800 2850N 2700 50E 6 ft. Tat 8ft. 9 ft. 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Pe = ~ 2M = a0 : Oy = » (ee 2 SSS aa | = SS gion (ae aoe oe oe er ae = Pe ae eeee re Cee oer Miia SON <3 YX \ é ONS: Sores A YS SS VSM ASSIS Sods ORIN WALSALL {i doy YS OP) Fea PUPIPPINNG MAPA Yfppes i eg FPL ALISA IGS NINN Soe PR Se Wy = PY) 7 . en Ze a ae ae MIE: 1 SN TA PP tat wa ZEN, \S38 < Le a « ee RN Scale 10) 10 20 30 40 50 Feet : Beitr TRANsEcT oF AESTUARIAL Marsu 1050 to 1100 Bast os VA Spartina pateris KN \ { Juncus Gerardu il Asptdium thelypterts aes Scurpus americanus ‘ tree 23 Spartina glabra (except near 5008) PLATE XXII JOHNSON AND NU PLATE Xxil JOHNSON AND YORK. oO aN a a =. Qun 2 SS Nad & NBN 2 NS a a % eNO ah Pies > a 3 ms o Se n nA? Hn WD nn NS nm No WY. SECTION IV. 2 a \ Se WS NOS X f a ” Sor es \ a S EX \ Bett TRANSECT OF AESTUARIAL Marsu 1050 to 1100 Easr. 50 Feet 40 20 6. DESCRIPTION AND MAP (PLATES XXI AND XXII) OF BELT TRANSECT OF THE MARSH (FROM 1.5 TO 10 FEET), SHOWING THE DISTRIBUTION OF THE VEGE- TATION EXISTING IN 1909-1910. By Henry S. CONARD, AIDED BY PAUL M. CoLLINS AND CHARLES W. PALMER. We will give at the start a brief explanation of the construction of the map, plates xxr and xx11. Then, after noting the topography of the area studied, will take up the zonation of its vegetation in detail. 1, EXPLANATION OF PLATES XXI AND XXII. This map represents a minute study of a portion of the Marsh at the head of the Inner Harbor, by means of a belt transect (Clements, 1905, pp. 178-179). The belt is 50 feet wide and extends from the wagon-road on the south to the open water of the harbor on the north. It lies on the general map between 1,050 east and 1,100 east, and 525 south and 100 north. This belt was chosen because it represents the greatest diversity of vegetation, together with the most distinct zonation. Stakes were set every 50 feet along each side. Then with tape-lines and graduated rods the exact boundaries of the vegetative areas were plotted in strips 5 feet wide. Every plant was located when isolated or not forming a prominent part of a society. For example, every individual plant is given for the following species: Asclepias incarnata, Atriplex arenaria, Hibiscus mos- cheutos, Hypericum perforatum, Iva oraria, Myrica gale, Oenothera biennis, Prunus serotina, Rubus alleghemensis, Rumex crispus, Sambucus canadensis, Vaccinium pennsylvanicum. Several other species are located where they occur sparsely, or on the margins of their areas, but are put in diagrammatically where plentiful. This serves to show the limits of distribution and the areas of dominance. Such species are: Aspidium thelypterts, Atriplex patula hastata, Distichlis spicata, Juncus gerardi, Salicornia europea, Scirpus americanus, Solidago sempervirens, Spar- tina glabra alterniflora, S. patens, Sueda maritima. Carex tenera, Eleocharis olivacea, and Limonium carolinianum are marked where sparse, but are not designated on the map where more plentiful. They are mentioned in the description of the various belts. In every case the mark on the map is much larger in proportion than is the plant itself. This is a mechanical necessity. Hence also many small gregarious species must be diagrammatically shown. Gregarious species which do not become dominant are: Aster nove-belqu, A. subulatus, Atriplex patula hastata (in favorable places), Distichlis spicata, Gerardia marituma, Impatiens biflora, Juncus gerard: (when outlying), Lileopsis lineata, Lysvmachia terrestris (in favorable places), Plantago decipiens, Polygonum maritimum, Salicornia europea (in places), Scirpus nanus, Spergularia marina, Triglochin maritima. Diagrammatic representation was alone possible for many plants which occur scattered more or less profusely throughout a community. Such are: Aster 113 114 THE RELATION OF PLANTS TO TIDE-LEVELS nove-belgii, Carex tenera, Eleocharis olivacea, Hrechtites hieracifolius, Hypert- cum virginicum, H. canadense, H. mutilum, Impatiens biflora, Limonium carolinianum (in places), Lysimachia terrestris, Spartina patens (in belts of Juncus, Scirpus, or Spartina glabra). Some of the above list are not marked on the map at all. Where a series of parallel lines represents a species (¢. g., Spartina patens), the lines are drawn farther apart where the plant is less plentiful. For symbols not explained on plate xxi see Table F, page 153. 2. DESCRIPTION OF THE STRIP. A. THE LIE OF THE LAND. The wagon-road on the south of the strip is macadamized, and occupies a causeway built about 6 feet above the level of the Marsh. The bank slopes down to the Marsh as steeply as the earth and gravel of which it is made would lie, that is, about 30°. The foot of the bank is about 9 feet above mean low water. Very high winter tides wash much débris as far as this bank. Thus beds of dead stems of Spartina glabra and occasional timbers 6 inches in diameter may be found anywhere over our area. From the foot of the bank to the %-foot contour the Marsh forms a smooth plain. The only irregularities are the occasional tide-pools and mud-flats marked on the map. The pools are flat-bottomed depressions of 4 to 6 inches depth. The margins are usually vertical, but sometimes the bottom of a narrow arm of such a pool rises gently to the level of the surrounding sod, forming a mud-flat. Other mud-flats of this region are not connected with any depression. At about the 7-foot contour, in our area, the ground falls off rapidly, or even abruptly. This contour marks the beginning of the dominant and pure growths of Spartina glabra. B. THE PLANT COVERING IN DETAIL. The vegetation of this strip shows several well-marked zones, or belts, which may be designated along the east side of the strip as follows: i. Wmoadside-graga «Belt: 2.5 eecce Oe ee 516 south to 497 south. Dy *ECOTT “BGIL, vote ok ee a ihe a aie oie eee 497 south to 450 south. 33 RCW DUS OMeTICUNUS Hell... 2.07. seen 450 south to 340 south. 4. :Jduncas-Snarting’ Belt. 500.23 ore eee 340 south to 93 south. 5. Spartina patens Belt. aia. aele ae 93 south to 18 north. Se Distichiis ( Belt’, e754 a aineereee cae: 18 north to 28 north. 7. Spartina glabra Muhl. var. alternifiora (Lidisel) Merr. te. cars, Agee ees eee ee 28 north to 70 north. 1. THE ROADSIDE GRASS BELT OR BELT OF AGRICULTURAL GRASSES. This area presents a uniform appearance as of a rather sterile and neglected grassy meadow (fig. 1). The grasses are denser and taller on the 2 feet of level ground at the edge of the roadbed. This area is at once seeded and fertilized by washings of manure from the road. The dominant species is Agrostis alba, which grows about 20 inches tall. With it occur: pS tay ae } subdominant. Dactylis glomerata Agropyron repens sparse. Panicum sp. « All measurements of height of vegetation were made after July 15, 1910. BELT TRANSECT OF THE MARSH Tas Agropyron attains a height of 30 inches. Dotted here and there occur: Acalypha virginica. Hypericum perforatum. Rhus toxicodendron. Ambrosia artemisiifolia. Juncus tenuis. Rubus allegheniensis. Aster sp.? Lactuca sp. Rumex acetosella. Barbarea vulgaris. Melilotus atba. crispus. Carex, 2 spp. Oenothera biennis. Solidago canadensis. Cerastium vulgatum. Oxalis stricta. Taraxacum officinale. Chrysanthemum tleucanthe- Plantago lanceolata. Trifolium agrarium. mum. Potentilla argentea. pratense, Daucus carota. Prunus serotina (2 plants). Vaccinium pennsylwani- Dianthus armeria. Pyrus malus (1 small cum. Erigeron canadense. plant). Various mosses. So far as these species are indicated on the map, every individual is noted. At the foot of the bank where moisture is plentiful we find also: Asclepias incarnata (3.3 feet tall). Lysimachia terrestris. Hupatorium perfoliatum. Myrica gale (3.8 feet tall). Hibiscus moscheutos (3.4 feet tall). Polygonum sagittatum. Impatiens bijfiora. Scirpus americanus. Lycopus americanus. The most peculiar feature of this belt, perhaps, is the group of Scirpus americanus which is found 3 feet up the bank, among the grasses. This, together with Hibiscus and Myrica, owes its presence to the nearness of the salt sea-water. The other plants are such as might be expected on any roadside bank in the Piedmont region of the northeastern United States. The total number of species in Belt I is 45. 2..THE FERN BELT. Associated with a seepage of fresh water which comes in at the southeast corner of the Marsh, there is a large bed of Aspidiwm thelypterts of dense and luxuriant growth. Overtopping the fern is a sparse but (in our area) universal fringe of Scirpus americanus. The ferns are about 2 feet tall, and easily domi- nate their area (plates XIX A and x1xB). Their border is very sharply defined. They stop off suddenly both south and north without diminution in size or fre- quency. Outside of this belt only 4 plants of this species occur, namely, at 398 south by 1,072 east, 403 south by 1,081 east, 448 south by 1,098 east, 449 south by 1,089 east. This is doubtless due to the fact that the fern usually spreads by rhizomes, and only rarely by spores. The fern area does not extend quite across the belt. At the middle of the belt there is a narrow strip of marsh between the foot of the road-bank and the ferns. This strip is occupied by a dense and luxuriant growth of Lysimachia terrestris, Aster nove-belgu, and Impatiens biflora, the first being dominant and the last least numerous. With these, Myrica gale and Hupatorium perfoliatum occur as noted on the map. At 492 south and about 1,095 east are two telegraph poles. Between them is a strong bush of Sambucus canadensis. 'This doubtless sprang from a seed dropped by a bird which perched on one of the poles. Seeds dropped in this way are frequent on the marsh. One bird excrement was found containing 11 cherry seeds (probably Prunus serotina). Other plants found among the ferns are: 116 THE RELATION OF PLANTS TO TIDE-LEVELS Scirpus americanus (subdominant, Aster nove-belgii f t averaging 3.2 feet tall, with an occa- Impatiens biflora } kage sional maximum of 5.3 feet). Panicum sp. (scattered Agropyron repens (beside the tele- RHoeron Dis as picket: poles). Galium claytoni pias incarnata June d i Eupatorium perfoliatum -as charted. PO ice cna etie Myrica gale Selaginell (gumantss ; : nine elaginelia apus plants). Erechtites hieracifolius. A liverwort (Pallavicinia). abundant. near southeast corner only. Hypericum canadense mutilum virginicum Atriplex patula hastata occurs frequently, but the plants are slender and etiolated, with narrow, erect leaves. They are hopelessly overshadowed by other plants. Total number of spermatophytic species 19; of pteridophytes 2. 3. THE SCIRPUS AMERICANUS BELT. Scirpus americanus occurs from the foot of the road-bank to about 345 south, being plentiful throughout this area, and of an average height of about 1 meter. Its inner margin is determined by the road-bank. The outer margin, however, is hardly less distinct. For though the plants become fewer and shorter (2.5 feet), they greatly overtop their companion species. The outlying individuals were easily plotted (plate x1x B). This plant has already been noted as subdominant in the fern area. In the middle of its range it is clearly dominant. Toward its outer borders it is dominant only in appearance. In number of individuals it is greatly exceeded by Spartina patens. This grass, beginning at the margin of the ferns in some places, becomes more plentiful by imperceptible gradations, until it becomes dominant, and finally pure (345 south, Belt IV). In the south and east half of Belt III, Lysimachia terrestris and Hypericum virginicum are frequent at the southeast, becoming sparse toward north and west. Hrechtites hieractfolius is abundant (about every 4 or 5 feet in August 1909) over the southern two-thirds of the belt. The limits of these plants are shown on the map. Impatiens biflora has two outlying representatives at 450 by 1,075 and 445 by 1,050. Single plants occur of Asclepias incarnata, Aspidium thelypterts (as already noted), Carex lurida, Epilobium coloratum, Hibiscus moscheutos, Hypericum canadense, H. mutilum, Myrica gale. Trifolium agrarium and Rumezx crispus occur at the foot of the road-bank on the south. Carex tenera and Eleocharts olwacea are frequent in the north and northwest portions, the latter species extending as far south as 450 feet and 1,077 east. Eleocharis becomes subdominant about 350 south to 360 south and 1,050 east to 1,062 east. Another bed of it occurs at 400 south and 1,075 east. Carex tenera is abundant about 350 south to 355 south, where Scirpus is becoming decidedly sparse. It grows about 2 feet tall. Panicum is sparse throughout this zone. Lycopus americanus is represented by 2 or 3 plants near 400 south. Oscillatoria was noted on the moist ground at 340 south. * One square foot near the middle of our third belt was occupied (August 4, 1911) by 48 Scirpus americanus, 31 Carex tenera, 6 Aster, 1 Erechtites, 234 Hleocharis olivacea, 128 Spartina patens. One square foot in the densest patch of Scirpus ameri- canus contained 88 stalks of that species, and 32 Spartina patens, 1 Carex, 2 unidenti fied grasses, 1 Acer rubrum (first year seedling). BELT TRANSECT OF THE MARSH 117 A boardwalk runs obliquely across the northern border of the Scirpus belt. It is built partly on a low ridge of gravel, hauled in for the purpose, and partly on posts. The gravel forms a strip about 4 inches above the level of the Marsh, and about 5 feet wide. The boards occupy a width of about 2 feet, and the plants for 2 feet on either side of them are kept mowed off with a scythe to a height of about 3 inches. These conditions have greatly affected the adjacent vegetation. Asclepias incarnata is especially abundant on the south side of the barrier. Juncus gerard is scattered about in the Scirpus belt north of the walk. Between the boards and on the gravel occur: Agropyron resens. Distichlis spicata. Rhus toxicodendron. Ambrosia artemisiifolia. Erechtites hieracifolius. Rumesx acetosella. Anaphalis margaritacea. Fragaria virginiana. crispus seedlings. Asclepias incarnata. Lactuca sp. Scirpus americanus. Aspidium thelypteris. Lycopus virginicus. Solidago sempervirens. Aster nove-belgii. Myrica gale. Spartina patens. Atriplex patula hastata. Plantago lanceolata. - Paraxacum officinale. Bidens frondosa. major. Verbascum thapsus. Carex tenera. Prunus serotina. Dactylis glomerata. Rubus allegheniensis. Total number of spermatophytes aside from boardwalk area, 20; pterido- phytes, 1; additional species along boardwalk, 21; total, 42, 4, JUNCUS-SPARTINA BELT, The fourth belt is in every way much broken and diversified. It extends from the limits of Scirpus americanus to the pure growth of Spartina patens at 95 to 150 south. The 8-foot contour cuts its northern border. Many small tide- pools and naked mud-flats break the continuity of the spermatophytic vegeta- tion. With these exceptions, nearly all of the area is covered with Spartina patens. In places this is pure, but other large areas are distinctly dominated by Juncus Gerardi. So dense is the Juncus as to give the impression of a pure growth.* Its brown fruits, over-topping Spartina patens by 1.5 to 2 dm., give it a characteristic appearance which is noticeable a hundred yards away. But except in some few patches, Spartina is always mingled with Juncus. On the southern border of our belt, Juncus is scattered through the Scirpus zone as far as the boardwalk. Juncus also occurs scattered in the Spartina areas in several places. But the boundaries of the Juncus patches are usually very sharp and easily recorded. At 150 south and 1,100 east is a mixture of Juncus and Spartina which it seemed best to describe as Juncus with a mingling of Spar- tina (see plate xx11). There is a distinct tendency for the tide-pools to be bordered by Spartina rather than by Juncus. But in several cases one plant borders one side and the other borders the opposite side of the same pool. The average height of Juncus is 4.5 to 5 dm.; of Spartina 2 to 3.5 dm. or rarely 4.5 dm. In three places (150 south and 1,050 east, 200 to 250 south, 295 to 300 2 On 5 different plots of 4 square inches each there were counted (August 1911): SUNCUS QETATAT . dane. tbs cn ee i's 30 12 5 20 Sporting patens. 05 «sie as sees 3 0 0 1 2 Aster. eu bulatis.. ives + 2eees2 0 0 0 0 1 This gives an average of 604.8 Juncus per square foot. In pure growths, Spartina patens averages about 1,400 stalks per square foot. Actual counts gave on 4 square inches, 40 and 43 stalks, and on 16 square inches, 151 stalks. 118 THE RELATION OF PLANTS TO TIDE-LEVELS south, and 1,100 east) Spartina glabra occurs scattered among the Juncus. It seems to have extended, probably by rhizomes, from denser areas outside the belt. In all such cases it looks starved, and is not over 3 dm. tall. Between 200 and 250 south, Spartina patens patches also contain Spartina glabra. There is no evidence of antagonism between the two. In smaller numbers and more restricted areas several interesting maritime plants occur in this belt. Gerardia maritima forms distinct beds. Where it occurs, the grass or rush is of very short stature, not over a decimeter, or may be wholly absent. Mud, often containing small pebbles, is visible between the plants. As the grass or rush gradually becomes taller around the Gerardia patch, the Gerardias become less numerous, taller (up to 2 dm.), and later in flowering. This is evidently due to shading of Gerardia by the competitor, reduction of light inducing taller growth, and reduction of temperature causing later germination and slower maturation. At 150 to 160 south, Gerardia is accompanied by the much rarer T'riglochin marituma. ‘This plant occurs only in the midst of the spots where competition is least. It never, in this belt transect, exceeds 1.5 dm. in height. The indi- viduals are numerous — a hundred or more in each patch. They seem healthy, and flower and fruit freely. At one place about a dozen plants of Plantago decipiens are mingled with Gerardia and Triglochin (160 south and 1,090 east). These were observed in two successive years. They seem healthy, but are of only medium size, about a decimeter tall. In other parts of the Marsh this species attains a height of 1.5 dm. with many leaves and inflorescences to each plant, and T'riglochin reaches a height of 2 or 2.5 dm. Spergularia marina was first met at 298 south and 1,075 east—an isolated plant. It is established on the mud-flats about 100 south, in this zone, and on the margins of the next. There were in 1909 about a dozen individuals, 0.6 to -0.8 dm. tall, flowering and fruiting freely. This species and Plantago decipiens occur in greater luxuriance outside our belt transect on the inner margins of the Spartina glabra zone, where the mud is very sparsely settled by other plants. Spergularia was observed in our strip in these places and only in these, both in 1909 and 1910. Scirpus nanus, miniature but full grown, forms a bed at 122 south and 1,089 east. It is in the edge of a mud-flat, along with Distichlhs, Salicornia europea, and Atriplex patula hastata. This is much more exposed to sun and wind than the place it occupies in the inner border of the seventh belt. The scattering plants named above are all essentially gregarious, and not found everywhere. The following are very common members of the vegetation of protected shores, but occur often as isolated individuals: Salicorma europea makes its first appearance in the edge of the first large tide-pool (315 south by 1,075 east). In the area from 250 to 300 south many Salicornias were dead in 1909, apparently eaten by grasshoppers. Other individuals gave evidence of “ damping-off” at the base. The first healthy plants were 282 south and 1,085 east. Between 150 and 100 south many Salicornias were large and bushy—excellent specimens of the species. But others were dying at the tips, and some were quite dead. Even the best condi- tions south of 100 feet are evidently unfavorable to this species. BELT TRANSECT OF THE MARSH 119 Atriplex patula hastata was found in a starved condition in the shade of the ferns of the second belt. In the fourth belt it occurs with Salicornia in the edge of tide-pools and on mud-flats. The leaves spread out in the normal posi- tion and are of normal shape. At 250 to 275 south they were badly eaten by insects in 1909. The first healthy, bushy individuals in our strip, plants 3 dm. high and 2 to 3 dm. across, were in the edges of mud-flats between 100 and 150 south. But just east of our strip fine specimens occur at about 225 south. Inmonium carolinanum was first observed at 300 south and 1,070 east and again at 259 south by 1,068 east. These were small, feeble plants, not flowering. A group of stronger plants occurs at 215 south by 1,075 east. From this point northward the species becomes more frequent and more vigorous. In other places around the harbor it is quite able to hold its own in dense growths of Spartina patens and Distichls spicata. It is not hurt by such competition. Polygonum maritimum seedlings also occur around tide-pools and mud- flats, sometimes in great numbers. Only at 300 south by 1,075 east were they found flowering, and then as slender and weak plants, not over a decimeter tall. In other places on the Marsh a single plant of this species may be 1.5 or 2 dm. tall and as large in diameter. Distichlis spicata, though occurring along the boardwalk, may be said properly to begin with the tide-pools. It never looks starved, but occurs only in isolated stalks or small groups from 325 to 100 south. In the tide-pools at 100 south and 1,075 east and 110 south by 1,080 east it first shows itself as a real invader, spreading by vigorous straight rhizomes. It is nowhere dominant in this zone. Eleocharis olivacea does not come farther north than 313 south. Carex tenera was not noted outside the Scirpus belt, though it was frequent there. A single seedling of Iva oraria was recorded at 300 south and 1,075 east. It was not found in 1911. One small plant of Atriplex arenaria was observed on the edge of a mud-flat at 250 south and 1,079 east. Seedlings of Aster subulatus occur around the mud-flats and beds of Gerardia. Sueda maritima was noted along with Polygonum maritimum at 300 south by 1,075 east. This is our only record of this species in this belt. In a tide-pool in this belt were found seeds of Prunus and Rubus in bird droppings, and a walnut, a pine cone, and a fruit of Gleditsia, doubtless carried by water. In a pool at 320 south various Cyanophycee were noted. A bare spot shaded by grass at 315 south was covered with Vaucheria. In a pool at 200 south, and again at 125 south, Beggiatoa was found. Rhizocloniwm was seen partly covered with silt at 225 south, and abundant on the ground among Spartina patens at 115 south. The total number of species in this belt (20) is still considerable, but less than in any of the preceding belts. All of the phanerogams are such as inhabit only saline or brackish soils. 5. SPARTINA PATENS BELT. A nearly pure growth of Spartina patens extends from 100 south to 10+ north, being from the 8-foot contour nearly or quite to the 7-foot. This might be regarded as a large patch from the preceding zone. But its location and 120 THE RELATION OF PLANTS TO TIDE-LEVELS appearance in the whole Marsh mark it off as a distinct area. The grass is very dense and luxuriant, falling over late in the season into irregular hollows and ridges like “ licks ” on the hair of a cow. Its even, light-green color is especially pleasing to the eye. At 40 north and 1,050 east it reaches a height of 7 dm., 6 dm. at 25 north, and 5.2 dm. at 0 north. Outliers of Juncus gerard: extend only as far north as 81 south. Here the Spartina is only 3 to 4.5 dm. tall, and at 25 south it drops to 2 or 3dm. Aériplex patula hastata, Limonium carolin- anum, Solidago sempervirens, and Distichlis spicata are scattered about irregu- larly. Spartina glabra is scattered plentifully in one place, 0 north by 1,050 to 1,075 east. The southern border of the belt is exactly like the borders of patches in the preceding belt. At 110 south a large bed of Gerardia occurs, overlapping the border. On the east side the Spartina glabra belt projects into this. The north and west margins of the indentation are formed by the precipitous banks of a tide-creek, and the change of vegetation is correspond- ingly abrupt. The south margin isa sloping mud-flat. Here Distichlis spicata is established, and is vigorously invading. An isolated patch of Distichlis east of this may be a relic of an old mud-flat captured by the invading species and then cut off by a later advance of Spartina patens across the narrow isthmus. Will Spartina finally possess the patch and Distichhis withdraw? Atriplex patula hastata, Salicorma europea, and Spergularia marina occur in full development around this lobe of Spartina glabra. 'Total numbers of spermato- phytes, 10. In this belt Beggiatoa, both white and pink species, were noted in a pool at 40 south, on the contour of 6 feet 6 inches, together with Anabena and mats of Rhizoclomum. About the zero-line the grasses grow shorter and other plants are more numerous among the Spartina patens. Distichlis spicata in particular appears in rapidly increasing numbers and Spartina patens disappears by equal steps, giving way to the Distichlis belt. 6. THE DISTICHLIS BELT. For a short space Distichlis spicata is clearly dominant, but it is not sharply demarcated from the preceding belt. On the north, however, it stops with an abrupt but very irregular border at the edge of the tall Spartina glabra. The margin is fringed by runners of Distichlis advancing northward in the mud, and Spartina glabra has numerous outliers of one-half to one-fourth normal height in the borders of Distichlis. The narrow strip of soft brown mud (1 to 5 or 6 feet wide) which is not closely occupied by either grass is copiously overgrown with Salicorma europea, together with numerous Sueda maritima, Atriplex patula hastata, and an occasional Atriplex arenaria. Scirpus nanus forms dense mats beneath everything else at several places on the border; at the east edge of the belt this species is quite exposed, forming the sole vegetation over 1 or 2 square feet. Total number of Spermatophyta, 8. At 25 feet north Vaucheria thuretu forms dense tufts on the contour of 6 feet 4 inches, and Rhizoclonium was found on a block of wood at the level of 6 feet 6 inches at 25 north. BELT TRANSECT OF THE MARSH Tog. 7. SPARTINA GLABRA BELT. At 25 to 50 feet north, a tall growth (1 meter high) of Spartina glabra becomes the dominant vegetation. Nothing else is apparent. Its inner border has been described above; its outer border is the open water. The ground consists of a soft, brown, oozy mud, whose surface slopes decidedly toward the north. It is cut by many tide-channels from 3 to 18 inches deep. On close examination we find isolated shoots of Spartina patens as far as 10 or 15 feet north of the boundary of this zone. They are represented diagram- matically on the map, actually occurring much closer together than marked. Within 2 or 3 feet of the south margin, Distichlis spicata and Salicornia europea are plentiful. Scirpus nanus makes a dense growth on the west, just within the border of this zone. The most notable secondary species, however, is the tiny umbellifer Lileopsis lineata. Not over 0.4 dm. in height, it forms a dense sod on the west side of our belt, growing luxuriantly and flowering and fruiting freely. The shade of Spartina glabra and two daily baths with salt water seem to furnish the necessary conditions for its existence. It occurs here only, on our strip. Beyond this the seventh belt is a pure growth of Spartina glabra. It reaches a height of 9 dm. at 50 north and 13 dm. at 70 north. No other spermatophyte apparently can meet the conditions here. Total number of spermatophytes, 6. As this belt is the most constantly wet with salt water, it supports the smallest number of species. Are they the most specialized ? a Fifty stalks per square foot (33 on one, 68 on another sample foot). IV. FACTORS INFLUENCING THE DISTRIBUTION OF LITTORAL PLANTS. The factors which most directly condition the distribution of littoral plants in this harbor are: the character of the substratum, water-currents, tidal changes in level, salinity of the water, and (probably) the temperature of the water. We will consider these in the order mentioned. 1. SUBSTRATA. The substrata supporting plants of the shore and harbor bottom may be: (A) living plants or animals; (B) non-living substrata. A. LIVING SUBSTRATA (PLANTS OR ANIMALS). The only animal of great importance in serving as an attaching place for plants is the abundant black mussel, Mytilus edulis. This has become increas- ingly abundant in recent years and now nearly covers the bottom over some acres, in the region between 1,600 and 2,000 north by 200 to 1,000 east, and the region between 1,200 and 1,800 north by 200 and 400 west. As we stated in Chapter III, the young mussels become attached to the large sheets of Ulva by thousands, so as to make the bottom covered by the Ulva and its burden look black. The erectly standing mussels serve to catch the silt and organic débris that is drifting along near the bottom and thus the mussels become partially buried. As the shells of the mussels become larger, firmer, and rougher, the spores of Ulva and Hnteromorpha clathrata, settling upon them, give rise to numberless young sheets or threads of these alge, which wave back and forth above the upturned edges of the shells of this mollusk. It thus, in turn, becomes a substratum for more plants of the species on which the mussel itself first settled. The Ulva and EHnteromorpha then serve to still further retard the movement of the water near the bottom and thus increase the rate of silting up, until large areas may thus become covered with fine black mud to a depth of 2 feet or more. Other animal substrata supporting plants are the oyster Ostrea virginica, and the various gasteropod shells inhabited by hermit crabs. The oysters of the Inlet, for example, often bear plants of A gardhiella, Polysiphonia, or Ceramium in addition to the green alge found on the mussels. The plants that are most important in serving as substrata for other plants are Spartina glabra, Zostera, and Ulva. Most of the species found on Spartina, like the Lyngbyas, Microcoleus, Rhizoclonwum, and Vaucheria, are seldom attached by definite holdfasts, but simply tangled about each other over the stalks of this grass in mats. Rarely a few small plants of Ulva or Enteromorpha are found actually attached by holdfasts. Zostera really bears a more definitely specialized epiphytic flora than any other plant serving as a substratum. Any of the Zostera below mean low water, especially that subjected to the swifter tidal currents, may bear epiphytic tufts 122 SUBSTRATA 123 of the diatoms Melosira and Navicula, of Enteromorpha clathrata, and still more frequent tufts of the red alge Ceramiuwm rubrum and C. strictum. A single leaf of Zostera may often bear two or three dozen tufts of these various alow, and the leaves are often broken off by the weight of this load, to be finally stranded on the beach. The two Ceramiums are practically confined to the Zostera. Aside from an occasional plant, on a pebble or shell in the Inlet, these Floridez find no other resting-place in this mud-bottomed harbor. In addition to these larger forms, Zostera may bear thousands of small, sedentary diatoms, like Cocconeis, and sometimes many square feet of a stand of Zostera may have the leaves fastened together and weighted down by the gelatinous colonies of a Spirulina. Ulva serves not merely for the attachment of Cocconeis and other diatoms occurring singly or in very small colonies, but may occasionally bear young plants of Enteromorpha clathrata and may also be weighted down by the gelat- inous colonies of Spartina just mentioned. Besides the three important species above mentioned that may serve as sub- strata for epiphytes, many seed plants of the upper littoral belt, such as Sali- cornia, Sueda, and especially Spartina patens, may, like Spartina glabra, have felts of Rhizoclonwwm and various blue-green alge tangled about their stems. Finally, any alga in the harbor, if of considerable size, may bear epiphytic diatoms of various species. B. NON-LIVING SUBSTRATA. By far the larger number of species found in the Inner Harbor, aside perhaps from the diatoms, grow on a non-living substratum of either purely inorganic or partly organic origin. These non-living substrata may be grouped as follows: (1) soils, including gravel, sand, mud, humus, and peat, among the constituent particles of which the holdfasts, 7. ¢., roots and rhizomes, of the seed plants are embedded; (2) solid substrata, including rock, stones, pebbles, shells, and wood. ‘To the surfaces of these the holdfasts of the various alge are attached without penetrating appreciably into their substance. Of course, it is evident that felt-forming alge like Lyngbya, Rhizoclonwum, etc., may grow on the surface of peat, sand, or gravel. But to these alge, since they do not penetrate these substrata, the latter are the equivalent of solid substrata. The pebble of the south shore of the Spit is to a Calothrix what a stone of the wharf is to a Fucus or Ascophyllum. 1. Sorts AS SUBSTRATA (GRAVEL, SAND, Mup, HUMUS, OR PEAT). The soils about the harbor differ in fineness from fine silt or mud up to sand, or even pretty coarse gravel. They differ largely also in the proportion of organic content from nearly pure sand or gravel to humus and peat with a very large proportion of material of organic origin. _ There is a very distinct horizontal zonation evident in the general distribution of soils about the natural shores of the Inner Harbor from the bottom up to the 10 or 12-foot level. As has been mentioned in speaking of the distribution of Zostera, the portions of the bottom lying below 1 foot are chiefly of a sandy, shelly, or pebbly character. The deep hole near 1,400 north by 600 east, and the deeper parts of the channel leading to the Outer Harbor, have a bottom of 14 THE RELATION OF PLANTS TO TIDE-LEVELS sand and shell fragments which are shifted about by the swift current at each ebb and flow of the tide. The only plants discovered here are those of Ulva, Polysiphonia, Agardhiella, etc., which are drifting along and dragging with them the pebbles or shells to which they are attached. To the south and the east of this deep hole there is a considerable area of bottom below the 1-foot level that is covered with a decimeter or more of mud overlying the gravel and which is occupied pretty completely by Zostera. (See plate 1.) To the west of this depression lies the tide-channel that starts at the Research Laboratory. This channel has a bottom somewhat below —1 foot, with a mud bottom, which also bears more or less scattered Zostera. From the —1 foot level up to the lower margin of the Spartina at 1.5 feet practically the whole bottom is of soft brown or black mud. The only exceptions to this are the gravelly east shore of the Inlet, from 1,600 to 2,400 north, and the bed of the Creek, from 100 south to 400 or 500 north. The depth of the mud over the gravelly bottom which underlies the whole Inner Harbor, varies from a decimeter or two up to 1.5 or even 2 meters. The only plants really growing on or in this mud, aside from the diatoms coating certain areas, are Zostera, which gets above mean low water near 600 north by 500 east, and Ruppia, which ranges from mean low water up to +1 foot. The alge found growing here on scattered shells, pebbles, or sunken stakes, or on the living mussels, are really rendered thus quite independent of the nature of the bottom. The same thing is true of the floating tangles of Hnteromorpha and sheets of Ulwa. The character of the bottom from +1.5 feet up to about 6.5 feet is pretty constant about the whole harbor, except where changed by entering streams or artificially modified. These levels of the shore consist of a fine-grained, peat- like mud that is more or less firmly bound together by the living and dead rhizomes and roots of Spartina glabra, which forms a nearly continuous belt on all natural shores at these levels. The distribution of the Spartina, shown in plate 1, indicates that of this type of bottom. Only on recently formed gravelly shoals (e. g., near 200 north by 600 east) or at points where smaller entering streams have cut away this peat down to the underlying gravel, or where bathing beaches have been constructed, is this type of bottom wanting about the whole harbor. Along the south shore of the Spit from 800 west to 400 east, it is true, as was noted earlier in the paper, that this peaty bottom does not reach quite down to the 1.5-foot level. The depth of this peat, which usually tapers out to nothing between the 6-foot and 7-foot levels, may be as much as from 3 to 7 dm. in the lower half of the Spartina belt. A series of soundings with an iron rod, along a north-and-south line at 10 west, showed a thickness of this layer which at first increased and then decreased in going shoreward from the 2-foot level, in the way indicated in plate v. Essentially the same thickness of peat covers the gravelly bottom on the east and west shores, as is shown by the actual sections of the peat cut by the rivulets entering the harbor over the upper beach (e. g., that at 1,650 north by 800 west). This layer of peat or peaty mud on which the Spartina flourishes is not of the same consistency throughout its thickness. The upper 2 or 3 dm. are firm and fibrous, while the portion below this is far more liquid, so that the upper layer shakes or quakes with the stamp of the foot. The living rhizomes never penetrate far into this less-solid lower layer, which is but little more firm than SUBSTRATA 1D the mud covering the bottom of the harbor. The upper, 7. e., inshore, edge of the peat belt becomes fairly well drained at low water, due largely to the number of burrows of the fiddler crab Gelasumus pugilator. Toward the middle and lower edge of the Spartina belt the soil is less firm and is poorly drained, except close to the edge of stream-channels and, in some places, along its own abrupt lower border, at the 1.5-foot level. In these places only do the fiddler-crab burrows, and an occasional muskrat burrow, afford some drainage and an opportunity for aeration. The only plants usually occurring on this peaty soil besides Spartina glabra are the alge Rhizoclonium, Enteromorpha clathrata, Fucus vesiculosus spiralis, and occasionally Lyngbyas, which are matted about the Spartina stalks or over the mud. Near the upper margin of this zone of soil, however, occasional inwandering seed plants from the higher levels may be encountered. Of these the most often found are Solidago sempervirens and Sueda. | On the gravelly soils of the stream-beds there occur Lileopsis at 3 to 5 feet Triglochin and Plantago decipiens near 6 feet, and the alge Hnteromorpha intestinalis, Monostroma, Ilea, and Hildenbrandia. The soil of the zone above the 6.5-foot level differs much more at different parts of the boundary of the harbor than that below this level, the character at each point depending apparently on the supply of fresh water and on the plant- covering of the same part of the shore just above high-tide level. On the Spit, e. g., the soils above 8 feet are sandy and dry. In correlation with this we often find between 6.5 and 8 feet a sandy or gravelly soil, with little humus, occupied by felts of alge or by Salicornia and Sueda. Trese gravelly and sandy stretches are perhaps due primarily to wave-action, for when the dead Spartina stalks have been broken off in the fall, the waves raised by the strong winter winds beat with considerable force against this south shore of the Spit. Alternating with these areas of gravelly soil stretches containing more humus are found, which are occupied chiefly by Spartina patens and INstichlis. On the shaded west shore, and on the east shore south of the mill, we find these levels, except for the narrow stream-beds, furnished with a damp, humus- containing soil that is sometimes very peat-like in character. This usually grades off insensibly below into the peaty substratum of the Spartina glabra. Above this there is often a sharp cliff-like drop at the boundary between the soil of this belt and the soil of the supra-littoral belt, near the 7.5-foot or 8-foot level. At the bottom of this little escarpment, of a decimeter or two in height, the gravelly or sandy subsoil is often nearly bare of mud. The vegeta- tion of this soil of the upper littoral belt on the east and west shores consists in the better-drained areas, chiefly of Spartina patens, and where fresh water is present chiefly of Scirpus americanus. In with these are scattered Scirpus robustus (near fresh water), Solidago sempervirens, and, on more sandy areas, Spergularia (plates x1r and x111). Along the rivulets and streams plants of the supra-littoral belt may push down below the 8-foot level. Along the southern boundary of the harbor, at the north edge of the Marsh, the most marked change in the character of the soil in passing upward from the 6.5-foot level is in the greater firmness and probably larger percentage of organic content of the soil, as it rises abruptly from the 6-foot to the 7-foot level and then slopes up very gradually to the 8-foot or 9-foot level. The upper layer of 126 THE RELATION OF PLANTS TO TIDE-LEVELS soil on this gently sloping portion consists of 2 or 3 dm. of tough, black, fibrous peat, bound together by the dead and living rhizomes and roots of the Spartina patens, of Distichlis, and of Scirpus americanus, by which this part of the Marsh is chiefly covered. A study of the subsoil of this Marsh, by the aid of the section cut out by the Creek, as well as by several series of soundings made with an iron sounding-rod, shows that the firm superficial layer of the peat is under- laid by one of soft, black, peaty mud, of a thickness varying from 1 to 10 or 15 dm. Beneath this is a layer of firm sand or gravel, with a very uneven upper surface, perhaps due to the covering up with the soft muck, of a delta cut by many channels. (See fig. 3, p. 111, which gives a north-and-south section at 1,100 east, as reconstructed from soundings by Professor York and Mr. Paul Collins.) The muck below the surface here is, in consistency, much like that at the bottom of the harbor, and that underlying the firm surface peat of the Spartina border about the barbor. The soil of levels above high-water mark differs very greatly on different sides of the harbor. On the Spit, e. g., there are large areas where the surface layers, at least, are of nearly pure sand, only partially fixed by the tufts of Ammophila and occasional clumps of Solidago sempervirens. In depressions near the top of the Spit, however, e. g., near 500 east and 800 west, there are patches of firmer soil, rich in humus, and supporting a considerable variety of plants. In fact, wherever a tree or a group of bushes becomes established on the Spit humus accumulates and the soil 1s held together, so that such areas may be left standing considerably above the rest of the surface, which is lowered by the removal or sand by winds and waves. This is true, e. g., of the area about the Robinia near 600 west, of that about the group of Ailanthus near 100 east, and of that about the group of hus at 540 east. The soil above the 8-foot level on the east and west shores of the harbor, aside from the gravelly artificial surfaces of the wharves, is not much affected by the proximity of the sea. In many places it is springy, wet, and shaded, and most of the plants on it are species found in inland wooded swamps, though Scirpus americanus does push up the streams to 9 or 10 feet. In drier, sunny places, beach-plants, such as Solidago and Atriplex patula hastata, may crowd up among the upland forms to as high as the 8.5 or 9 foot level. On the Marsh, as we have seen in Section III, the character of the soil and the vegetation changes rather gradually in going southward from the middle of the Marsh at 8 feet to the foot of the causeway embankment at 9.5 feet. These changes in soil and in plant-covering are indicated more precisely in the detailed maps of the Marsh (plates x1, xx1, and xx11). The relation of the vegetation to the substratum is too complex and the causes of its detailed distribution too incompletely understood to make it worth while to take it up in any detail again here, after what has been said earlier in this paper. In general summary of the relation of the distribution of plants to soils in the harbor, it must be considered as evident: (1) That the sparsity of attached algee on the bottom of the harbor must be due chiefly to the lack of larger particles in the soft mud to which plants like the rockweeds and red alge can become attached. Similar tidal basins in the neighborhood, having stony bottoms, show a much more varied algal flora (e. g., Center Island and Lloyd’s Point). (2) The peaty mud, commonly found between the 1.5 and 6.5 foot levels, is dominated by Spratina glabra, with only a subordinate ground-covering SUBSTRATA LAT of green and blue-green alge. Since, however, this Spartina grows luxuriantly in this neighborhood in nearly pure sand, it seems more probable that the Spar- tina determines the character of the soil rather than that the latter conditions the occurrence of the grass at these levels in our harbor, that is, the thick stand of salt reed-grass, between the tidal limits endured by it, favors the deposit of organic as well as inorganic sediment on the surface and also adds considerable organic material by the decay of its own roots and rhizomes within the soil. (3) In the case of the higher levels of the Marsh there seems to be a definite dependence of the character of the plant-covering on the salinity of the soil- water and on the depth of the peat-like layer of top soil. (See fig. 3.) While Spartina patens may grow from the 7.5-foot to the 8-foot level, in peat with soil-water of a salinity or specific gravity of 1.017+- at this same level, and in soil of otherwise the same character, except that the soil-water has a shghtly lower specific gravity, the plant-covering consists primarily of Distichlis. If near the higher level mentioned the salinity of the soil-water gets below 1.006, these two grasses are often replaced by Scirpus americanus. (4) The soil differences of most importance in their effect on plant distribution in the two belts between the 6.5-foot and the 12-foot levels on the north, east, and west sides of the Harbor are those in salinity of soil-water, and, especially on the Spit, differences in the amount of humus in the soil. 2. SoLIp SUBSTRATA (STONES, PEBBLES, SHELLS, PILES, AND Logs). The most important of the solid substrata in our harbor are the pebbles of the natural bottom of the Inlet and the stone walls and wooden piles and docklogs of the wharves. The scattered stakes and the shells and occasional stones of the bottom are far less important as plant substrata, the one exception to this latter statement being the shells of living mussels mentioned earlier, with their hundreds or thousands of young plants of Ulva and Cladophora. The pebbles of the Inlet consist of well-rounded bits of quartz, granite, gneiss, sandstone, or conglomerate, of all sizes up to 1 or 2 dm. in diameter (plate xviIr). No adequate evidence was obtained of a marked preference of any of the algee for one material among these pebbles rather than another. The Chlorophy- cee, Hnteromorpha clathrata and Ulva, and red alge, such as Agardhiella, Chon- drus, Gracilaria, Hildenbrandia, and Polysiphomia, are found more commonly on the smaller, smooth, quartz pebbles, which make up the larger portion of the possible attaching surface on the bottom of the Inlet. The Phzophycee, Ascophyllum and Fucus, on the contrary, are usually found on the larger, rough- surfaced bits of granite or sandstone. It is probable that with the growth of the plants of the rockweeds that happen to start on smaller pebbles the supports are ultimately dragged away by these plants and thus either washed upon the beach or buried in the mud of the bottom of the harbor. This may account for the few quartz pebbles found bearing Fucus or Ascophyllum. Ulva starting on these smaller pebbles may likewise grow and finally drag off the latter. In other cases if the pebble is firmly fixed among its fellows or is too large to be dragged away by the plant, the growing sheet of Ulva may be torn loose and float or drift about over the bottom. In fact, the incrusting alge, such as Calothriz, Ralfsia, and Hildenbrandia, which grow on the large stones as well as the small, the rough as well as the smooth ones, are the only species which may not finally drag off their supports if the latter happen to be small. 9 128 THE RELATION OF PLANTS TO TIDE-LEVELS The stone of the wharves about the harbor is chiefly a brown sandstone. There are, however, numbers of large blocks of granite and gneiss scattered among the brownstones of the wharf on the east side, from 1,000 north to 1,600 north. Certain yellowish blocks of this granite and gneiss are constantly bare of Ascophyllum and Fucus, though all the surrounding stones of otherwise similar character and the brownstone blocks are densely covered by these alge (plate 111). As no differences could be discovered in the chemical or physical charac- ters of the barren and the alga-covered rocks (see p. 70), we have no explanation to suggest for the striking difference in their alga population. In speaking of the gravelly soils above the 6.5-foot level, we have mentioned that Calothriz, Lyngbya, or Microcoleus are attached to the surfaces of the pebbles of the upper littoral beach, forming “ Phycochromaceta ” of Warming (1909, p.175). These simple forms are attached to the surfaces of these fine pebbles and sand grains just as the larger alge of lower levels grow on the larger pebbles of the Inlet, or of the channels of fresh-water rivulets along the shore (plate x). The wooden channel-stakes of the middle of the harbor form, as was noted just above, a restricted but often densely populated substratum for numerous alge. Thus a single stake may bear, attached to its bark, or, in older stakes, to the bared wood, groups of tufts of Melosira, Navicula, Ulva, Enteromorpha clathrata, Ralfsia, Dasya, Grinnellia, and Porphyra, besides felts or tangles of Rhizoclonium mingled with various blue-green alge. On the larger piles and wharf-logs and on bits of heavy wreckage along the shore, the algal population may be much richer in both individuals and species. Thus, e. g., the vertical chestnut piles of the wharf of the Research Laboratory may bear a dense drapery of rockweeds, any gaps in which are largely occupied by felts of Lyngbyas and Rhizocloniums, by warty incrustations of Ralfsia, by an occasional Porphyra, or by dense colonies of Bostrychia. In the winter Ulothrix flacca becomes prominent on these same piles. Near high-water level occur bands of felted ' Lyngbyas and tufts of Calothriz. All of these alge, except the finer-felted ones, are attached to the firmer parts of the wood, and careful study of sections of the holdfasts of Ascophyllum and Fucus, of Bostrychia and Porphyra, show that these do not really penetrate into the tissue of the wood, but simply spread over the surface and into the furrows between the harder strands of the wood. The wooden wharf-logs are generally too near high-water level to bear much rock- weed, but they often have an abundant felt or tangle of Rhizocloniwm even at the 8-foot level when on the north side or where the log is kept moist. At the 8-foot level on logs and stones of the Research Wharf grew the only species of lichen found near high-water mark. This lichen, Lecanora subfusca, occurs also at this same level on stakes on the Marsh. 2. THE INFLUENCE OF WATER-CURRENTS. Under this head are included the effects of water-movement in streams, tidal currents, and waves. Such water-currents may affect the distribution of plants directly, as by wafting about the plankton of the surface and the drifting plants of the bottom, or by the dispersal of the spores or seeds when shed. They may also cause injury or even the total destruction of plants on shores or wharves by carrying ice against them or dropping flood-trash upon them. On the other hand, these currents may affect plants secondarily, by determining either the character of the substratum, the different degrees of aeration of the water over different areas, and finally by a favorable or unfavorable effect on competitors. WATER-CURRENTS 129 The plankton organisms, such as the Diatomacee and Peridinee, are often drifted together in certain corners of the harbor by tidal currents and winds till they color the water deeply, while other parts of the harbor are comparatively free from these plants. The distribution of many Chlorophycee and Floridee that are free or attached to small supports is changing constantly and they drift with the tide. The ultimate results of this drifting is often the stranding of these plants so high up on the bottom or shore of the harbor that they are killed by exposure. We have mentioned in detail in Section III (pp. 18, 21), the repeated redistribution of plants or fragments of Ulva and E'nteromorpha clathrata, and the same process must be very active in the case of Fucus vesi- culosus spiralts in late winter and early spring, when the wearing off of the dead stalks of Spartina by ice and waves has left the Fucus free. It is evident that spores or seeds discharged into moving water may be carried to very considerable distances by it. The seeds or spores of plants, e. g., those living in the tidal channels, must thus be distributed widely over most or all of the habitats suitable for them, as well as over many others. We suggested above (p. 32) that certain Floridex, of sporadic occurrence in the Inner Harbor, probably arise from spores which are brought in by the tide from neighboring areas in the Outer Harbor, where they are present year after year. A very interesting question that arises here, which can be answered by experiment only, is whether these spores can become attached to surfaces of stone, shell, or wood while the tidal currents are still running, or whether it is only for a short time at slack-water that an effective holdfast can be developed. The cases of alge like [lea and Monostroma, in streams near high-water level, are of especial interest in this connection, since the only period of slack-water in these habitats is that at high water, and then the pebbles on which the spores are to start are surrounded by salt water. The fresh water of the streams at this time, as was shown by Miss Streeter, runs out on the surface of the harbor, leaving salt water next the bottom.* It may prove true that the spores of these plants, which are to live most of the time in fresh water, do, and perhaps can, germinate only in salt water. If this is the case it would offer an interesting explanation of the fact that these alge do not spread up the streams beyond the high-water mark. In winter, when ice is abundant in the harbor, the plants of the shore, and especially the alge on the piles and walls of the wharves, are subjected to pretty serious grinding by the cakes of ice and may even be frozen into the ice during very cold weather and then torn off. Tufts of Spartina glabra, a meter square, were found in July 1910, many yards away from the nearest Spartina. In 1910, e. g., the small tuft at 2,200 north by 750 west was a newcomer. The only plausible explanation we can offer of the appearance of this tuft in an area which in 1909 was totally bare of Spartina is that ice froze about the stalks of the plant at high tide, in early winter, and that later, with a higher tide, the clump of the grass, with the peat-mass on which it grew, was lifted bodily and floated by the ice to its present position. In this case the grass has persisted for two (or three) seasons. In other cases, where the turf is dropped in the middle of the harbor, 1. e., in deeper water, it does not flourish, probably because of too 8 Our tests of the Creek at high water of an 8-foot tide showed the presence, just above the bottom, of a stratum of water about 1 foot thick with a density of 1.020 which extended upstream to 600 south. A layer about 2 feet in thickness next above this had a density varying from 1.020 to 1.014. The water at the surface upstream from 450 south is entirely fresh, while from this point northward it increases in salinity to a density of 1.010 at 50 north. 130 THE RELATION OF PLANTS TO TIDE-LEVELS great a proportionate submergence. The alge on the mud among the Spartina, such as Fucus vesiculosus spiralis (plate xv1), Rhizoclonium, etc., apparently suffer also from the winter waves, aided by the ice. At least they are relatively scarce in the early spring. On the banks of tide channels, e. g., on the west side of the Inlet, or on the concave banks of the Creek (near 100 south) the turfs of grasses are often under- mined by the swift current and many pieces fall into the water to be carried away. Large numbers of plants and very considerable areas of soil are thus destroyed. Another way in which tidal currents and waves may injure plants is by covering them with tide-trash so deeply as to smother them out. Instances in which Spartina glabra, S. patens, Salicornia, and other species are thus destroyed over areas of several square meters are mentioned in Section ITI. Of the secondary effects of water-currents on submerged plants, the most important is probably the effect of this movement on the concentration, in the water about the plant, of solutions of useful and injurious gases or solids, and on the rate of interchange between the plant and the immediately surrounding water. It is a well-known fact that the hard bottoms of swift-flowing tide- creeks, or bottoms just below low-tide mark on wave-beaten shores, have an unusually luxuriant algal flora. While this is partly due to the stony bottom found under swiftly moving water, yet it is evidently attributable partly to the effect of the agitation of the water on the plants themselves. It is probable that all of the effects above mentioned are of importance. But no one, so far as we know, has yet proved experimentally whether the movement of the water is more important in simply increasing the rate of interchange of material between the plant and the surrounding water, or in bringing to the plant solutions of substances needed by it and removing waste substances cast off from it. The action of the waves in floating out the tangles of rockweed of the mid-littoral ‘belt, and of then keeping them in almost constant motion, indicates that both a better aeration of the water and a higher rate of interchange of nutrient and waste substances between water and plant must result. These would be very interesting points to settle definitely by carefully checked physiological experiments. The influence of water-movement on a plant may also be exercised second- arily through the favorable or unfavorable effect of this movement on its competitors. For example, it is evident that the inability of large sheets of Ulva to withstand the strong current in the Inlet prevents the huge sheets of this species from covering large areas of the bottom here, as it does in the quieter parts of the Inner Harbor, and thus prevents it from smothering out many of the species that now find congenial conditions in the Inlet. On the other hand, the drifting by the tide of the rolls of Ulva mentioned on page 20, and the final settling of these on patches of Zostera and Ruppia, may smother these latter out in the same way that the masses of Ulva, Enteromorpha clath- rata, or of other tide-trash, have been shown to smother Spartina glabra, and the algal felts with it, in the mid-littoral belt. It is probable that it is the inability of other brackish-water alge to gain, or maintain, a foothold in such a swift current that gives Ilea fulvescens such undisputed sway on the steeper pebbly bottoms of the Creek between 150 south and 500 south. TIDAL CHANGES Fel 3. THE CHARACTER OF TIDAL CHANGES AND THEIR INFLUENCE ON PLANT DISTRIBUTION. In the earlier sections we have repeatedly referred to various effects of the tidal changes in water-level on individual species of plants. We may now look more closely into the magnitude of the tidal changes in water-level and the ways in which the latter may affect the growth, and other physiological activities, of littoral plants, and thus aid in determining their distribution. These peculiari- ties and effects of the semi-daily rise and fall of the tide may be discussed under the following heads: (A) Characters of the Tides; (B) Effect of Tidal changes on Evaporation; (C) Effect on Aeration; (D) Effect on Salinity of Soil-Water at High Levels; (EK) Effect on Exposure to Rain; (F) Effect on Light Supply. In addition to the effects just enumerated the tides cause part of the water- currents that are referred to above and also have an influence on the salinity and the temperature of the water of the harbor in general, which are to be discussed below. A. CHARACTER AND MAGNITUDE OF THE TIDES. The predicted, semi-diurnal range in water-level, due to tides, varied during the growing season of 1911 from 4.2 feet to 10.8 feet. (See plate xxiv, and Tittman, 1910.) The “mean range” during this season was 7.63 feet. This mean range varies from year to year, and the one here given for the growing season of 1911 is about 0.1 foot below the “ corrected mean range” for three or four decades. The smaller or “ neap range” occurs just after the first and third quarters of the moon in each month. This neap range varied, during the months from May to October 1911, from 4.2 feet on October 1 to 7.0 feet on June 20. The greater or “ spring range” occurs just after the new moon and the full moon. This varied in 1911 from 8.5 feet on July 14 (and 8.6 feet on June 10) to 10.8 feet on May 27. (It was 10.7 feet on October 10 and even 11 feet on April 30, the day before the beginning of our somewhat arbitrarily fixed growing season.) These various facts are indicated graphically in plate xx1tv. The chart there shown was constructed from data given in the U.S. Tide Tables above referred to. (See also tables A, B, and C, pp. 135, 136.) Of course, the high water actually occurring at Cold Spring Harbor may sometimes be higher than that predicted, because of a northerly wind blowing the water into this long, narrow harbor. Or on another day high water may be lowered by a southerly wind retarding the inward flow of the water at flood-tide. On the other hand, the height of a low tide may be lowered: by a strong southerly wind or kept above the predicted height by the retarding effect of a northerly wind during ebb tide. In the long run, however, this influence of the wind in modifying the water-level at high and at low tide would prove about equal in both directions, and so the actual tides would show an average or mean range corresponding closely with that of the predicted tides. It must be remembered that any effect of a general prevalence of winds from one direction, é. g., from the southwest in summer, is one of the factors included in the actual tides observed at Cold Spring Harbor in 1894, on which observations the prediction of tides for this station is based. The general effect of the semi-diurnal variation of water-level, with high and low tides, on the vegetation of the shores, is probably dependent (see p. 14 1382 THE RELATION OF PLANTS TO TIDE-LEVELS above) chiefly on the average or mean range of the tides from end to end of the growing season. For plants growing just below mean low water or just above mean high water it is probable that the occasional extremely. low tides or extremely high tides may be of great, possibly of preponderating or critical, im- portance (see p. 15 above). We shall look into this latter question in more detail later on. It is evident that the direct primary effect of this oscillation of the water- level, twice each “lunar day” of 24.9 hours, will be the twice repeated sub- mergence by the water and exposure to the air of all plants growing between tide-marks. While the roots and submerged portions of the shoot are under water they are wholly or partially shut off from the light and completely shut off from a supply of air, except as this may be conveyed to them from the exposed portions or absorbed from the submerging water. ‘The possible secondary effects of this submergence and exposure we shall attempt to analyze later on. The determination of the exact time of submergence and exposure of soils and plants at the various levels necessitates carefully made and recorded observations of the rate of rise and fall of the tide. Since no such data for the Inner Harbor at Cold Spring Harbor were available, measurements were made in the manner described on pages 12 to 14 above. These measurements are expressed in the curve shown in plate v1, which was briefly described earlier in this paper (p. 13), in order that the data embodied in it might be used in the discussions in Section III. The chart referred to gives the curve for two successive tides of a single lunar day. ‘The tides chosen are of about mean range. From this chart the sub- mergence and exposure, by an average tide, of all levels of the shore between mean low water and +-7 feet, might be determined. But in order that the aver- age submergence and exposure during the growing season of these levels, and of levels lower and higher than these, might be determined, records of all tides, ‘from May to October, were needed. Since we were unable to make these by actual measurement at Cold Spring Harbor, recourse was had to the records of actual tides, and especially to the predicted tide curves, for Willet’s Point, New York. This is the nearest tide-recording station of the U.S. Coast and Geodetic Survey and is the “ standard port for reference ” for Cold Spring Harbor. An actual recorded curve for Willet’s Point for July 18, 1894, is shown in the chart in figure 4.° This shows the form of curve for a tide of mean range. This curve has the general form of that for the tide of mean range at Cold Spring Harbor, though it shows a slight flattening at the top, and a striking retardation in the rate of fall of the water-level just before mean low water is reached. Plate xx11I shows a portion of the “ predicted tide curve ” for May 1911, made by the tide- predicting machine of the Coast and Geodetic Survey. In these predicted curves for tides at Willet’s Point those for mean tides show a close resemblance to the curve of the actual mean tide at Cold Spring Harbor. We may, then, assume, what is highly probable, that the curves of actual tides of neap range and of spring range at Cold Spring Harbor would resemble in general those for the same tides at Willet’s Point, just as the curves *The writers are greatly indebted to Mr. O. H. Tittman, Superintendent of the Survey, for his kindness in having the curves of actual tides traced and in having the predicted curves, for the season from May 1 to October 31, 1911, made anew for us, by the new tide-predicting machine of the Survey. JOHNSON AND YOR PLATE XXIII. Feet ; 9 Predicted tide q 4 May Ist-5th.19 7 2 Mean sea level. ay 3rd. iSe20 21 19bL the day JOHNSON AND YORK. PLATE XXIll. Feet . : 9 Predicted tide curve 3 May Ist-Sth. 1911. / 7 / LEE as 6 5 ib 4\— Mean sea level May1,ISI! ___Mean sea level. 3 Ruretio 2. Asp RTS 96 oy © 6) & io “I 12-213 me ies Jame 8 19 aD Wie tan eee is 19 20 2 22 2 ip y * 0 Mean low water ee * os a _ Sa =F Feet 9 8 7 —— I 6 ~ ee E : * aA : \ ye \ 4 eee , May! 4th. ig h Mean sea level / : May 5th. 3 : Soe eat] ai Ea ae eae 7 ps) DE GE | Mac SG Wee cs on i chee eo a PEN 0) Eee Gulia oS, 9> 10 Me > / SS , Mean low water Ss 25 we Curve Suowrne Portion oF THE PREDICTED TIDE CURVE FOR WILLET’s Point, N.Y, For May 1911. Made by the tide predicting machine of the U. 8. Coast and Geodetic Survey, on March ikfi, TSB This curve shows the form of the curve for tides of different range, also the marked difference in range of the day and night tides of the same lunar day. SUBMERGENCE AND EXPOSURE ino of actual mean tides at the former station were found to resemble those for the same tides at the latter station.* If, then, we allow for the 0.4 foot greater height of high water at Cold Spring Harbor, we can, from this predicted curve for Willet’s Point, determine with sufficient accuracy the probable duration of submergence and of exposure of any level between tide-marks at Cold Spring Harbor. That is, we can determine by measurement, between the points of intersection of the horizontal line representing any level with the curve, the submergence and exposure of that level per lunar day per month, and so the total for the whole season of six months. Table A, page 135, gives the duration of submergence and emergence, per lunar day and per average calendar month, for various levels from —1.25 feet to +9.00 feet measured from this predicted curve. This table shows in the second and third columns the average total submergence in hours per month of each level. The emergence of levels below mean low water and the submergence N00 RC SO - ON Ae ee a a a ee Na INEM TR Gs RG A Pe Se mmm tL Oe a EE a SC a 2 Ve EET SS 7 Fe TE 0 Time IZPM. 1AM. 24M. 3AM. 4AM. SAM. 6AM. 7A.M. BA.M. 9AM, IOA.M, A.M. 12M. 12M. 2PM. 32M. 4PM. SPM. 6PM. 72M. SPM. OPM. IORM, HRM, 122M. Fic. 4.—Chart of tidal-curve of two successive mean tides, recorded at Willet’s Point, New York, on July 18, 1894 (supplied by the U. S. Coast and Geodetic Survey). (In comparing this curve with that in plate XIV note that the horizontal unit of the scale, representing an hour of time, is 20 per cent greater than the vertical unit, representing a foot in height, instead of equal to it, as in plate XIV. This accounts in part for the greater flattening of the crest and hollow of the curve.) of levels above 6.5 feet was measured on the predicted curve for Willet’s Point for all tides of the season. In determining the submergence and exposure of levels from 5 feet upward, allowance was made for the greater height of high water at Cold Spring Harbor, by measuring the submergence for each level at 0.4 feet lower down from the crest of the curve of the tide for that day, or by measuring it on the curve of a tide of proper height, though it happened to be on another day. The durations so obtained when divided by 6 give the average durations of submergence or emergence for each month of the growing season. The submergence of the lower levels was obtained by subtracting the total * Actual records of the tides of the Inner Harbor at Cold Spring Harbor were made with a tide-gage loaned by the U. S. Coast and Geodetic Survey, in July, August, and September, 1913. The form of this curve corresponds very closely with the con- structed curve shown in plate v1 and with the predicted tide-curve for Willet’s Point. The most striking peculiarity of the curve recorded at Cold Spring Harbor in 1913 is the sharpness of the trough at low water. This probably means that the times of “ihe given on page 136, for plants growing near mean low water are slightly too large. 134 THE RELATION OF PLANTS TO TIDE-LEVELS monthly emergence from 736.5, the average total number of hours in each month. The emergence for the higher levels was obtained by subtracting the monthly submergence from the average number of hours in a month. The exposure of any level varies greatly, of course, from month to month. Thus, e. g., the —1-foot level was not exposed at all in August 1911, while its probable emergence for May was 9.5 hours. Again, the probable submergence of the 8.75- foot level for August 1911 was 0.0 hours, while for May it was 11.25 hours. The average monthly emergence of levels between mean low water and 3 feet was obtained by measurement on the predicted tide-curve for Willet’s Point for August, since the mean low water for this month (0.038 foot) was closest to that for the whole six months of the growing season (0.006 foot). The submergence of levels between 4 feet and 6.5 feet was obtained by measurement on the predicted curve for June 1911, since the average high water for this month was exactly that for the season (7.63 feet). The fourth and fifth columns of Table A show respectively the average emergence and submergence per lunar day of 24.88 hours, there being 29.6 lunar days per month, or 177.5 lunar days per growing-season. From these data, or those for the month, the total emergence or submergence for each of the 59 tides per month (average) or 355 tides per season can be obtained. The sixth column of Table A gives the ratio of emergence to submergence for each level. These figures will be of value when discussing the upper and lower limits of plant distribution (see Section VI), since from them we can see the proportion of submergence to emergence endured by any plant at its upper or at its lower limit. Another series of tidal data of interest in connection with plant distribution is that concerning the frequency of submergence or emergence respectively of levels near the upper margin and the lower margin of the littoral region. From - the predicted heights of the low waters and of the high waters for each tide of the season, given in the United States Tide Tables for Cold Spring Harbor, it is possible to determine exactly the number of tides each month, or the total num- ber per season, in which any level near high-water mark will probably be submerged, or any level near low-water mark will probably be exposed, the only uncertainty in these cases being the possible effect of the wind in making the level attained higher or lower than that predicted. Table B (p. 186) shows the number of submergences per month and per season (May to October) of levels from 6 to 9 feet. These numbers were obtained directly from the Tide Tables by adding the 0.4-foot correction to the predicted high waters for Willet’s Point for each tide of the growing season. In connection with these numbers it should be recalled that there are 355 tides per season, which includes 58 each for June and September, 59 for October, and 60 each for May, July, and August. From this table of infrequent submergences can be deduced the duration of the longer continuous emergences of these high | levels. Table C (p. 186) shows the number of emergences per month and per season of levels between —1.25 feet and +1.75 feet. These figures, like those in Table B, are taken from the heights of predicted low waters for Willet’s Point, which are in this case identical with those for Cold Spring Harbor. From the SUBMERGENCE AND EXPOSURE 185 frequency of emergence of each level here given the duration of the longer submergences of these low levels can be obtained. From Tables B and C it is evident that the — 1-foot level and all below it may be continuously submerged for a month at a time, e. g., during August. Even the 0-foot level may, as can be seen from the Tide Tables, be submerged con- tinuously for from 4 days at a time, in May, to 7 days in June or August. On the other hand, the higher levels may be exposed continuously, never being wet by the tides, for many days together. Thus, e. g., in 1911, the 8-foot level was continuously exposed for 10 days in June, or even 12 days in July. Even the 7.5-foot level may be exposed continuously for 4 days at a time, in June, or even 7 days, as from August 30 to September 6, 1911. For levels above 8 feet the duration of continuous exposure would evidently be markedly greater. These unusual tides which submerge the higher levels and expose the lower ones are grouped in two series each month, 1. e., at the two periods of spring tides. This fact is of great importance to the plants growing at these levels. It means that plants at the —1-foot level, e. g., may be constantly submerged for a month at a time and then, after three or four periods of exposure, of from half an hour to an hour per tide, they may again remain submerged for a fortnight or a month. So far as enduring submergence is concerned, this is probably equivalent for the plant to constant submergence. The plant is, however, obliged occasionally to withstand the exposure to sun and wind. In fact, even such a brief exposure may be of critical importance in limiting the upward extension of a delicate species. With so much of general discussion of the tidal changes themselves, we may now turn to take up their effect on plants. TABLE A.—Duration of submergence and exposure, from May 1 to October $1, 1911. 1 Max, 5.5; min. 0.0. 2 This means that this level is exposed only z}, as long as it is submerged. 3 Max. 9.5; min, 5.0. 4 Max. 34.50; min. 12.5. 5 This means that this level is exposed 353 time as long as it is submerged. 6 June. 7 Season. - AON Sabo pear owe Average Average Ratio. Level. Average per cal-| Average per cal: eed Se ob ae Sale Emergence. endar month. | endar month. | P&* *U24 Gay. | per lunar day. Submergence. Feet Hours. Hours Hours. Hours. —1.25 1.66 1 734.84 0.06 24.82 1.66/734.84= 0.0023 2 —1.00 3.70 3 732.80 0.12 24.76 Bat MponOE= OUD tL —0.50 23.50 4 713.00 0.79 24.09 23.0 /113.0 = .0816 0.00 53.70 682.80 1.82 23 .06 ~53.7 /682.8 = .0788 +0.50 112.75 623.75 3.80 21.08 112..75/624.0 = .1791 +1.00 180.40 556.10 6.10 18.79 180.4 /556.0 = .38244 1.50 239 .25 497 .25 8.08 16.80 239).2/497.2°= .4807 2.00 261.25 475 .25 8.83 15.95 261.2 /475.2 = .65500 3.00 338.75 397.75 11.07 13.81 338.7 /397.7 = .852 4.00 397.50 339.00 6 13.43 11.45 397°5°/339.0 =" 1.172 5.00 461.50 275.00 15.59 9.29 461.5 /275.0 = 1.674 6.00 533 .62 202.88 18.03 6.85 533 .62/202.88= 2.625 6.25 559.50 177.00 18.55 6.33 559.5. /177.0 = 93.161 6.50 575.50 161.00 19.44 5.44 575.5 /161.0 = 3.574 6.75 601.50 135.00 20.32 4.56 601.5 /185.0 = 4.455 7.00 639.50 97.00 7A UB f 2.67 639.5 / 97.0 = 6.593 7.50 689.30 47.20 23 .28 1.60 689.3 / 47.2 = 14.60 8.00 706.14 80.367 23 .86 1.02 706.1 / 30.4 = 23.26 8.25 719.70 16.83 24.31 57 719.7:-/ 16.88= 42.76 8.50 727.80 8.70 24.59 .29 127-8: fe Sal == 8S..65 8.75 731.86 4.64 24.78 -16 731.86/ 4.64=157 51 9.00 734.42 2.08 24.81 .07 734.42/ 2.08=853.09 5 136 THE RELATION OF PLANTS TO TIDE-LEVELS TABLE B.—Number of submergences per calendar month and for the season, from May 1 to October 31, 1911. {In each column, under the name of the month (or the season), the figures give the number of times that the level in question is submerged during that month or during the season.] Lével May. June. July. Aug. Sept. Oct. Season. * | (60 tides.) (58 tides.) (60 tides.) (60 tides.) (58 tides.) (59 tides.) | (355 tides.) Feet Times. Times. Times. Times. Times. Times. Times. 6.00 60 58 60 60 55 58 351 6.25 60 58 60 56 52 57 343 6.50 60 58 60 54 52 53 337 6.75 59 58 54 51 43 46 3ll 7.00 52 54 52 44 43 39 284 7.25 39 39 44 37 87 33 229 7.50 33 33 38 34 So 30 200 7.75 26 24 28 28 26 23 165 8.00 23 14 21 22 21 20 121 8.25 11 7 6 12 15 14 65 8.50 8 5 3 2 5 ff 30 8.75 7 4 0 0 3 4 18 9.00 5 0 0 0 1 4 10 TABLE C.—Number of exposures per calendar month and for the season, from May 1 to October 31, 1911, of levels from—1.25 feet to 1.75 feet. May. June. July. Aug. Sept. Oct. Season. (60 tides.) (58 tides.) (60 tides.) (60 tides.) (58 tides.) (59 tides.) | (355 tides.) Times. Times. Times. Times. Times. Times. 1 0 0 0 3 9 3 2 0 3 4 17 9 6 14 17 17 79 26 27 28 28 27 165 48 52 43 40 36 264 58 60 55 48 46 323 58 60 59 53 53 343 58 60 60 56 55 348 58 60 60 58 59 355 .B. EFFECT OF TIDAL CHANGES IN WATER-LEVEL ON EVAPORATION OR TRANSPIRATION FROM THE PLANT. It is, in the first place, clear that when delicate, thin-cuticled plants like Zostera or Ulva are exposed at low tide during a warm, sunny day, they may be subjected to a dangerous desiccation. This desiccation, to which plants grow- ing above mean low water are liable, is undoubtedly concerned with determining the upper limit of distribution of such species. As has been mentioned in Section III, many plants of Cladophora, Entero- morpha, and Ulva, of various red seaweeds, and the leaves of Zostera, are often killed off by drying out on hot days in summer. The Ulva is oftenest destroyed by being floated to the higher levels of the beach by the air bubbles that collect under it on a hot day. We have spoken also (p. 91) of the drying out, and cracking to polygonal, tile-like blocks, of the felts of Schizophyceew and Chlorophycee occurring on the south shore of the Spit, between the 6.5 and 7.5 foot levels. At slightly higher levels these felts are usually wanting, probably chiefly because they and the soil bearing them are less frequently wet by the high tides, but are exposed to desiccation for a longer time. That the relative dryness of these higher levels really determines the absence of these algal felts seems clearly indicated by the fact that these felts may occur above their usual level when on the north or shady side of tufts of grasses, e. g., at 7.5 to 8 feet, on the top of the stone pier on the eastern shore. PLATE XXIV, A ie) 2 Gl re ee) oe oe be oo od ee) oe me aeun AAA AA ae BaRe MA COO 436 MANA NAN oe VV VVVV VV y Say AHHH Nua VVVVVVVV VV" | PLATE XXIV, JOHNSON AND YORK. | 249m 2: OMe 2 7 28 fn 29 30 if is 4a ey Ge eS oh als Tey 12 13] 14015 lef 7 rey. [he] fe, 22 2 3 ee 24 5 a 26m 27 2S 29 U CR Go OE + TV SEPTEMBER Site NAT AA A i fi A) AKA AAA 8FT, i) ” Crart SHOWING THE VARIATION IN RANGE oF TIDES THROUGHOUT THE GRowING SEason, CoLp SPRING HARBOR, FROM May 1 to OcrosBer 31, 1911. Tables, for Cold Spring Harbor. In the cases of May and June the varying degrees of coincidence of low tide with the hours of darkness and daylight are indicated by black bands for night and light ones for daytime. From this can be of time during daylight that plants at any level are above water. Oo MLW MLW TIDES AND EVAPORATION 137 For the alge growing on the vertical stone walls and piles of the wharves, also, the upper limit of distribution is evidently determined by the amount of desicca- tion the plants can withstand. We have seen, e. g., (pp. 65 and 67) that Rhizoclonium and Fucus go highest in crevices in the wharf, or on the north sides of piles, where not reached by the sun and by winds. In like manner, for erect-growing seed plants between tide-marks, like Spartina glabra, the elevation attained is evidently conditioned, at least in part, by the desiccation it is subjected to. That is, by the length of time at each tide that its leaves are exposed to the dry air. A clear indication that this is the case is found in the fact that on certain shaded areas with moist soil on the western shore, this grass grows at a level much above its usual upper limit. It displaces here its sun-loving competitor Scirpus americanus, which as usual holds sway at these higher levels on adjoining dry and sunny portions of the shore. That a grass with rather thick-cuticled, rolling leaves should be en- dangered by the amount of transpiration it can be subjected to just above the 6.5-foot level, while its rhizomes and roots are em- bedded in a practically saturated soil, seems surprising at first thought. But it is to be remembered that the humidity of the air about the upper half of the plant, which includes most of the well-developed leaves, may be quite low. This is especially true of the south shore of the Spit, which is just where the upper boundary of the Spartina is strikingly definite. That attempt was made to determine the evaporating power of the air in this habitat of Spartina on the Spit, and in several other typical habitats by means of a porous-cup atmometer. For this purpose three atmometers were used, whose coefficients of correction had been determined by comparison with a Livingston standard atmometer. All the readings here given are corrected readings, and may therefore be directly compared with the Liv- ingston standard. For use at levels where, because of the danger of submergence by the tides, exposures can be made for only a few hours at a time, except occasionally during a series of neap-tides, an atmometer is = Fi. 5. required which will indicate very small losses of water. For this i tetera purpose the porous cup was attached to the shorter arm of a tige-marks. U-tube, the other arm of which was graduated to tenths of a centimeter by filling from a burette. The resulting instrument (fig. 5) is a simplified form of that described by Livingston 1906. Three instruments of this kind, which we will designate as Nos. 1, 2, and 3, were run simultaneously for a week in an instrument shelter, to discover possible leaks and to check up their relative rates. _ For three days in August 1909, during a series of neap tides, the three atmometers were exposed in different places and simultaneous readings made at the beginning and the end of each of the following periods: August 6, 11°00" a. m. to 12°40" p. m.; August 7, 7°20" a. m. to 12°20” p. m., and August 7, 12°20” p. m. to August 8, 7°30" a.m. The total exposure for each instrument was 25.8 hours. The days on which the exposures were made were clear. The temperature recorded by a Friez thermograph in the shelter ranged from 18° 188 THE RELATION OF PLANTS TO TIDE-LEVELS to 30° C., while the humidity recorded by a Friez hygrograph in the same place varied from 50 to 95 per cent. Atmometer No. 1, in the shelter, showed an average corrected rate of loss of 0.43 ¢.¢. per hour. It showed a minimum rate of 0.37 c.c. per hour in the period from 12"20™ p. m. August 7, to 7°30" a. m. on August 8, when the temperature ranged from 18° to 30° C., averaging 23.5° C., and the humidity ranged from 50 to 95 per cent, averaging 79 per cent. The maximum rate for this instrument of 0.75 c. c. per hour was shown on August 7 from 7°20" a. m. to 12°20” p. m., when the temperature ranged from 21° to 27° C., averaging 22.2°, and the humidity varied from 53 to 75 per cent, averaging 69 per cent. Atmometer No. 2, placed in a dense stand of Spartina glabra at 2,750 north by 290 east, with its cup at the 7.5-foot level and about 1.5 feet above the soil, gave an average corrected rate for the whole 25.8 hours of 0.79 c. c. per hour. The minimum rate at this station was shown for the period from August 7, 12°20” p. m. to August 8, 7°30" a. m., the temperature and humidity in the shelter for this period being those given above. This corrected minimum rate was 0.67 c.c. per hour. The maximum rate for No. 2 of 1.1 c. c. per hour was also shown in the same period and under the same conditions as the maximum for No. 1,7. e., on August 7, from 7°20” a. m. to 12°20™ p. m. Atmometer No. 3 was placed 10 feet south of No. 2 among the stems of Spartina, in a reclining position, with its cup 4 inches above the soil and at about the 6.3-foot level. The corrected rate of this instrument varied from 0.36 c.c. per hour to 0.63 c.c. It is interesting to note that the relative rate of this instrument varied from 0.5 to 1.7 times that of No. 1. This wide difference in rate of two instruments exposed simultaneously is probably due to the differences at the station for No. 3 in the direction and strength of the wind, and especially to the different amounts of water, from the preceding high tide, left clinging to _ the Spartina stalks at the beginning of the exposure. The amount of this adhering water would depend on the length of time since the tide receded from that level; also on the temperature and on the direction and strength of the wind, which might dry it off. It must be borne in mind, however, that the variations in evaporating power of the air here mentioned are entirely characteristic of locations between tide-marks, and are therefore real © factors in the environment of plants, which, like the alge on the mud and on stalks of the Spartina, live in these habitats.. Another series of records was made in which atmometer No. 1 was placed in the shelter, No. 2 was placed on the vertical stone wall, facing east, at 200 north by 80 west, near the 6.5-foot level, and thus near the upper edge of the rockweed belt, and No. 3 was placed at this same level on the north-facing wall at 10 south by 40 east. The three atmometers were exposed simultaneously during a total of 32.7 hours of daylight from July 27 to 30, 1909, in clear weather, while the temperature ranged from 22.8° to 34.4° C. (averaging 28° C.), and the humidity varied from 39 to 87 per cent (averaging 60 per cent). The record of No. 1 under these conditions showed an average corrected rate of 1.08 c. c. per hour (ranging from 0.89 to 1.56 c.c. per hour) ; No. 2 gave an average rate of 0.9 c.c. per hour (ranging from 0.5 to 1.16 ¢.c. per hour) ; while in No. 3 the rate averaged 0.72 c.c. per hour (ranging from 0.59 to 1.14 ¢e.c. per hour). TIDES AND EVAPORATION 1389 Other series of atmometer records were started, but, because of accidents or lack of time, were not made complete enough to be of significance. From what has been said it is evident that the maximum rate of evaporation of 1.1 c.c. per hour recorded in the middle of a moderately warm day, by an atmometer among the leaves of the Spartina glabra, indicates that these plants are at times subjected to a relatively high rate of evaporation. If we multiply this hourly rate by 168 we get a weekly rate, 185, that closely ap- proaches the highest average weekly evaporation-rate, for the growing-season, in the United States east of the Mississippi, given by Livingston (1911, p. 219). Kven the average hourly rate for atmometer No. 2 in the Spartina, which included one night in the total exposure of 25.8 hours, was 0.79 c.c. per hour, or 133 c. c. per week. This considerably exceeds the average weekly evaporation for the summer at New York City, as given by Livingston (1911, p. 213), and the weekly rate of 95.5 c.c. at 2 meters above the soil found by Fuller (1912, p. 426) in a mesophytic beech-maple forest of Indiana. In fact, it very closely approaches that given for Salt Lake City (Livingston, p. 210). It nearly equals also the average rate of 0.83 c.c. per hour given by Transeau (1908, p. 219) for his standard instrument, established in an open garden at Cold Spring Harbor. The rate of atmometer No. 2 in the Spartina for the period that included the afternoon and the night of August 7, was 0.67 c.c. per hour or 113 c.c. per week. This indicates the correctness of Transeau’s suggestion (1908, p. 227) that the low average rate of evaporation from his atmometer, placed at the 12-foot level, on top of the Spit, in 1907, was due to the very slight evaporation occurring there at night. | The rate of instrument No. 2, when placed on the wall of the wharf, amid the rockweed, against stones saturated by water, and only 5 feet above the muddy bottom, with its trickling rivulets, averaged 1.08 c.c. per hour, or 181.5 c.c. per week, while its maximum rate reached 195 c.c. per week. This indicates the high rate of evaporation to which the rockweeds, Rhizoclonium, Bostrychia, and the Schizophycee of the wharves may be subjected, during low tide. These _ rates in fact approach the rate for the area about Lake Erie (200 c. c. per week), which is the highest average weekly evaporation-rate given by Livingston (1911, p. 219) for any part of the United States east of Texas or the Dakotas. It is, of course, realized that the few atmometer records here given can be con- sidered adequate to do little more than indicate the importance of this evapora- tion-rate as a feature of the environment of shore-plants living between tide- marks. To get a really adequate idea of the importance of this factor in the environment of plants growing at any level, we must have records by quick-regis- tering atmometers exposed at that level from the moment it is bared by the fall- ing tide until it is just about to be covered by the rising tide. Moreover, readings must be made each hour or half hour of all exposures, night and day, from end to end of the season. When this is done, as it is hoped it may be soon at Cold Spring Harbor, it is believed that both the average rate, and, in some cases especially, the maximum rate of evaporation in their habitats will be found to be intimately concerned in determining the upper limit of distribution attained by many of the species growing between tide-marks. 140 THE RELATION OF PLANTS TO TIDE-LEVELS C. EFFECT OF TIDAL CHANGES ON AERATION. It is pretty certain that for thick-cuticled plants like the Spartina, Distichlis, Salicornia, Sueda, etc., the period of submergence at high tide is one during which there can be little interchange of gases between these plants and the sur- rounding medium. At this time the stomata of the shoot are closed by water and, during the whole time of submergence, the only supply of O and CO, available for the plant is probably that held in the air-canals of the shoot. In the case of Spartina glabra this stored supply occupies a considerable portion of the bulk of the shoot. The whole system of subterranean rhizomes and roots of these plants is dependent chiefly on the shoot for its supply of gases, since the heavy, fine-grained mud in which the rhizomes and roots, e. g., of Spartina glabra are embedded is practically impenetrable to gases, except along burrows of the fiddler crab (Gelastmus pugilator) or those of the muskrat (Fiber zbethicus). Of course, except at spring tides, the upper portions of the leaves of the higher plants of Spartina glabra will still be exposed at high water, and it is possible that, by means of the abundant air-canals, gases may be exchanged between all parts of the plant and the outside air. For the other species mentioned above, since they grow higher up on the shore, the air-supply is not cut off for so considerable a time as for Spartina glabra, though this deprivation must still be of some consequence, since such a plant, e. g., as Salicormia, will, on the average, be more or less completely submerged for from one-fifth to one-third the daylight hours of an average summer day. The effect of submergence on the physiological activities of such plants could probably best be determined by growing them in a tide-pond the level of which could be maintained at a constant level for any time desired. For seed plants like Zostera and Ruppia, whose upper limit is not far above mean low water, it is probable that the necessary gaseous interchange is accom- _ plished during submergence, through the thin-walled epidermal cells. The same thing is perhaps largely true for the alge growing between tide-marks. Most of these, e. g., the rockweeds, Rhizoclonium, and the Schizophycee, have more or less gelatinous cell-walls, which quickly dry on exposure and so form a nearly impermeable membrane over the surface. On many days, it is true, only the outer exposed branches of Fucus or Ascophyllum and perhaps of other alge become really dry on the surface. Hence there may be a considerable gaseous interchange occurring even during low tide, a point which can be certainly determined only by experiment. D. EFFECT OF TIDAL CHANGES ON SALINITY OF SOIL-WATER AT HIGHER LEVELS. One of the effects of tidal changes may be that of periodically increasing the salinity of the soil-water. Near the 8-foot level, e. g., are certain areas where, during neap tides, the soil is barely moistened by slowly seeping fresh water, but at the fortnightly spring tides the salinity of the soil-water of these areas is increased by the salt brought up by the high tides. The effect in these cases is _ probably not large. In the case of the fresh-water tributaries of the harbor, the change in salt-content with tides of varying height is probably much more important. For example, there are growing in the larger streams, between the 6-foot and 8-foot levels, alge such as Ilea and Hnteromorpha, which may be TIDES AND LIGHT SUPPLY 141 surrounded by pure fresh water continuously for 10 days and then, during 5 or 6 days of spring tides, be subjected to strongly saline water for from 1 to 2 hours at each high tide. As was suggested earlier, the effect of this submergence is probably not great, except on soils that are comparatively dry in the intervals between series of spring tides, since in wet soils the salt water occasionally flood- ing them probably does not penetrate far. On dry shores, however, there is a strip of soil between the 7.5 and 8.5 foot levels where the salt-content is probably increased during each series of neap tides. This may be brought about by the constant movement upward of the water in the soil by capillarity to levels above that of the high water of the neap tides. By the evaporation of the water from the soil the salt will continue to accumulate at the levels mentioned until the soil is flushed out by the high waters of the spring tides, or by rains. E, EFFECT OF TIDAL CHANGES IN EXPOSING PLANTS TO RAIN. On the effect of tidal changes in exposing plants to rain there are but few observations to record. It is evident that all shore and bottom plants above —1 foot may be subjected to a pretty thorough washing with fresh water by any heavy rain of the growing season that occurs during low tide. Many of these plants, like Spartina and the rockweeds, may be drenched with rain for 6 or 8 hours at a time and not suffer from it. We have noted above that Fucus and Ascophyllum may lie for several hours in pure fresh water at low tide. In the case of certain of the red seaweeds, however, such as the Ceramiums on the Zostera, and plants of Agardhiella, Chondria, and Polysiphonia, a drenching of this sort, especially if followed by exposure to a hot sun, may cause the death of the plant. Large portions of the great sheets of Ulva are frequently found dead after exposure to such conditions. In general, all observations thus far made seem to show that nearly all the plants found above mean low water may withstand a more or less protracted wetting with fresh water, though only a few like lea, Hnteromorpha intes- _ tinalis, and Ectocarpus do, as we have seen in Section III, actually live where subjected to this every day. F. EFFECT OF TIDAL CHANGES ON THE LIGHT-REACHING PLANTS. It is evident that even in clear water the effective solar energy reaching sub- merged plants or parts of plants is markedly lessened by each foot of water it must pass through. In water of the turbidity of that often found along the shores of our harbor it is probable that submergence of a plant in 2 feet or, some- times, even in 1 foot of water will practically put a stop to photosynthetic activity. In the middle of the harbor the water is usually less turbid. In fact, on real quiet days it may be very clear at and near low water. From what has just been said it is evident that plants growing below high- water mark must do most of their photosynthesis during low tide. A reference to plate xxiv will show that since, on half the days of each month, high water occurs near the middle of the day (1. e., between 9 a. m. and 3 p. m.), it is evident that the most effective sunlight is, on these days, cut off from plants below high- water level for a longer or shorter time. This would be most markedly true of plants nearer low-water mark, but still true in some degree of all plants below 142 THE RELATION OF PLANTS TO TIDE-LEVELS high-water mark. All these facts taken together show that for a plant growing, say, at the 4-foot level (7. ¢., near mean sea-level), the time for the most effective photosynthetic work, that is, the total duration per month of emergence during brightest daylight (9 a. m. to 3 p. m.) is reduced to about one-half that for a plant growing in the open, above high-tide level. In other words, while the exposure of an upland plant would be 6 hours in the middle of the day, that for plants at mean sea-level will vary from 0.25 to 6 hours per day, averaging 3 hours per day for the month or season. Since the 4-foot level mentioned is about the average level of the photosynthetically active leaves of the lowest plants of Spartina glabra we have, in the 3 hours’ exposure mentioned, the approximate light minimum endured by this grass. Just what part this re- duced lighting may play in determining the lower limit of distribution is uncertain. Plants which are left submerged for a longer time than this by planting them at mean low water on the harbor bottom die out in one season. The effects of the various factors that are changed by this longer submergence can only be distinguished and determined by more prolonged experimental work than we have yet been able to carry out. The above given proportions, of light-reaching plants at different levels, were determined from the predicted tide-curves for Willet’s Point, New York, from May 1 to October 31, 1911, which are described on page 131 above. This curve for Willet’s Point is the closest approximation to that for Cold Spring Harbor that can be obtained, the chief difference in the two being the 0.4 foot greater height of high water, which would tend to slightly decrease the time of lighting of levels from mean sea-level upward. ‘Table D gives the times of exposure per day of four selected levels to total daylight, 1. e., from sunrise to sunset, and to brightest light, 7. e., from 9 a. m. to 3 p. m., for the month of May 1911, deter- mined from the above-mentioned predicted tide-curve. TABLE D.—Daily exposure of various tide-levels to daylight. Exposure to total daylight. Exposure between 9 a. m. and 8 p. m. Level. Hae aayoe ee Average ex- mit, 7 i Average ex- posure per |e 52 ee eee ee posure mer Minimum. | Maximum. day. Minimum. | Maximum. day. Hours. Hours. Hours. Hours. Hours. Hours. 9 feet (and above).. 13.96 14.93 14.50 6.00 6.00 6.00 i LOC Se cae scareelets 12.35 14.68 14.02 4.00 6.00 5.54 Big6i LECT. 56,0: /Beisverauers 6 9.15 t 0.15 6.00 8.00 O20 TO0tis fetes 0.0 5.60 1.5 0.0 1.25 0.12 It is interesting to note here that the 0.0-foot level may not be exposed at all to daylight for 8 days at a time, and not be exposed at all between 9 a. m. and 3 p. m. for 25 days out of the month. In this connection, however, we must recall again the often great clearness of the water in the center of the harbor at low tide, which allows plants at and below this level to get rather intense light © at low water, even though submerged by a foot or more of water. Since in the case of extreme spring tides high water always occurs in the middle of the day, the 9-foot level, if submerged at all, is covered between 9 a. m. and 3 p. m., the hours of brightest daylight. SALINITY OF WATER 143 It is evident that the habitat of the lower plants of Spartina glabra really resembles that of shade plants, so far as light supply and moisture conditions are concerned. Though they do not show very striking differences in structure when compared with plants of the same species growing near its upper limit, some differences are discoverable. For example, the plants at the 2-foot level have weaker stalks, thinner and narrower leaves, thinner cuticle and _ less- developed photosynthetic tissue than plants at the 6-foot level. Of course, many plants growing at and below mean low-water level are decidedly like shade plants in many respects, as has been suggested by Warming (1909, p. 150). For example, Zostera and Ruppia have the attenuated form characteristic of plants etiolated by shade. In the case of the alge Ulva, Enteromorpha, Cladophora, etc., found near low-water mark the structure is not markedly different, so far as was noted, from that of the same species at the highest levels these attain, except that the latter are smaller (perhaps we may say more stunted in growth). This is probably due to the fact that plants on piles and wharves at higher levels are more likely to be torn with the fall of the tide than are plants that lie on the bottom. A careful statistical study of the size of plants, of their cells, or the thickness of their cell-walls, might show constant differences in plants at different levels not hitherto detected. On the other hand, plants at the 7-foot level may get the maximum exposure of 6 hours per day to brightest daylight on 24 days of the month and lose an hour and a half or more of this light on only 4 days per month. Thus plants like Spartina patens, Distichlis, Salicormia, and Sueda, growing between 6.5 and 7.5 feet, are probably not much affected » by the relatively small proportion of total daylight lost by submergence. The general conclusion must be, then, that the shortened light supply of plants subject to daily submergence must affect their physiology, their structure, and hence their possible vertical range, in a very considerable degree, especially if they grow at or below mean sea-level. The exact effect of different exposures to light on different species of these plants has yet to be determined experi- mentally. In summary of the various effects of tidal changes on plants, we find that these are of most general importance in affecting, first, the amount of transpiration ; second, the time available for gaseous interchange between the shoots and the air ; and, finally in limiting the light-supply and hence the effective photospnthetic activity of littoral plants. Of secondary and only occasional importance are the effects on concentration of the soil-water at high levels, and the exposure of plants near mean low water to rains during low tides. 4. THE SALINITY OF THE WATER OF THE HARBOR. The normal specific gravity of the water near the surface of the harbor, at high water, was found to be 1.022 (at 15° C.). The salinity, and so the specific gravity, varies somewhat with the state of the tide, and may become much lower than 1.022 at low water. This lowering of the specific gravity is evidently due to the large admixture of fresh water from tributary streams and springs. The inflow of this fresh water remains constant, except that from springs between tide-marks, while the volume of water in the harbor with which this is mixed decreases very rapidly with the falling of the tide. The cubic contents of the harbor at high water is about 42,000,000 cubic feet, while at mean low water 10 ( TABLE E.—Vertical distri COMPOSITION OF Tide Levels. 12 feet. Thallophytes. Vegetational Belts. Supra-Littoral Beach. Supra-Littoral Mar Species. Range.* Species. R 11 feet. 10 feet. 9 feet. 8 feet. Cladonia sp. | 9 to 12 s Lyngbya sp. 8 s Nostoc sp. 8.£ | | Supra-Littoral Belt. | 8 to 12 feet. (Storm Beach and Supra- Littoral Marsh.) 7 feet. 6.5 feet. ¢c Rhizoclonium tortuosum.........ee.ee0. ae coments S$. Calothrix,(4:sp3) <2\0cce sanescceure alviare lato cualeve ofalere ae 8 Microcoleus cht onoplastes rain sere UiAaisis Se aera s . CO ViAUCHETIR AED caictsls ow inw cc chats cy mee orelatereictarels ainiatetsiote e Enteromorpha intestinalis Esinieataperateratarciaioiate aeveictiers 8 Lyngbya (8 sp.)..... aisiaice shefaisie eteuatae einai @ Flea. fulveseens..... 0.56 2ss0008 Sipiasite mesiterers tee c Monostroma latissimum.........0...-2000. Rh we'eee $ Spirulina tenuissima sac css. sceeen eee ee Upper Littoral Belt. 6.5 to 8 feet. (On all shores.) CONrNOCUr SY Sion 6 feet. 5 feet. 4 feet. 3 feet. 2 feet. 1.5 feet. 1 foot. 0 foot=M. L.W. 2 foot. —2 feet. —83 feet. * The two numbers given under ‘‘range’’ indicate the levels (above mean low water) between which the on e Rhizoclonium tortuosum..............cceseeeeees ¢ Rhizoclonium riparium...........ccecsseessseses f Bostrychia rivularigs....ctecces cee eee None cM lothrix aeca., Acdses se os bis Saeiste se sipnte comnts S$ Anahena tortiloge 1.4.54. 0s assur easeneckas tore $s Lyngbya MOSUUALUL cies 'cc cease Set eeaicke oe eee eee s Microcoleus chthonoplastes.... gia tetas Slgisvelecebornn ents p Ralfsia clavata........... ee Sialetess niciatetckensratatataierors arcs r Hildenbrandia prototypus..............s00. Abt ce Enteromorpha intestinalis..............- a aelcicisinte euMonostroma. latissimum......,.200-cene ves eee e Ilea fulvescens.......... oa ciate crefavele eis sterss civ ate. ere esis O Vauch6ria :p; «shechande cco sansorreeacee ani n ees ‘ ce Cladophora expansa...... m siviole ais Sieve rersielsreiclelayenyeters = p Pylaiella littoralis robustus....... b sgieiddeseitaies ¢ ‘ ¢ Delesseria leprivril.? coco eee use lee tee eee SSRIVAIATIA BELA cicewes vets acces aoe eee ee © Porphyra laciniata... cece ter ee eee eee Abe DUH RAED OM ORR RWWA Om Mid-littoral Belt. 1.5 to 6.5 feet. Mid-littoral Marsh and Mid-littoral Rockweed Association. Gin I wr cr Ulva lactucaslatissining «sts... ess vs. occe cesses —5 ¢ Knteromorpha clathratac.......0.esoeeroueeerrente —1 ce, Hnteromorpha intestinalis..2. .\.;.o.scesseuen aie ee 2 0 p Ascophyllum nodosum,..sc.c...cet cheese ses de nel ~*T pi Fucts vesiculosus.) 2c cad. ecto oe ee arrays Se 0 r Porphyra paeeance siesa'e¢ oxb.0l'e shoves > leaner eet meee etetata oo : : rf Oeramium rubrum. adse- sear alee eee es = _ iti Hag os r Ceramium strictum.......ceccasccscserracessencs —2 (Lower Littoral and Sub- p Pylaiella littoralis robustus .............s0e20e0: —1.5 littoral Belts.) r Ohondrus Crispus... oc oc save dacs ccetentn e's eet ooae ; | p Ectocarpus confervoides. .....6c.sncecccccccccvecs 0 Fl r Hildeabrandia prototypus...........s+06 Misteisie leis —1 | y Agardhiella tenera erates. ste retids. ccc sc cces —1 S$ Spirulina: tentisslmaaioec-remoc eins skis are ea os ¢ 0 rf Delesseria leprieuriist...-..csecccss ccc ces cee cess =1 Melosira nummiloides.\ iesimisinweciss ras sawiciemacres : —1 Navicula grevill@iti... cose fecesenecers tect teats —1I p Ascophyllum nodosum, ss sess sccccdessadisscssvece p Fueus vesiculosus: cect ccke toceep es eee tear ais oe | p Fucus vesiculosus spiralis................ Beara eis | 1 The small letter before the name of each species shows to the eye, in glancing down the column, the phy 8 = Schizophycex, d = Dicotyledonez, and m = Monocotyledonex. ‘ion of more common plants. IGETATIONAL BELTS. | Cormophytes. | | Supra-Littoral Beach of Spit. Supra-Littoral Marsh. ————. | eee eee eee e.* | Species. Range.* | Species. Range.* | || m Ammophila arenaria....... 8.3 to 12 m Scirpus americanus........ 6.5 to 12 d Cakile edentula............ 8.5 11.5 Aspidium thelypteris.......| 8.5 12 d Solidago sempervirens..... 8 11.5 m Juncus Gerardi............. 7.3 8.8 ‘ d Lathyrus maritimus....... 10 11 i aed DALens. aise sees: 6.5 8.7 ? d Euphorbia polygonifolia... 8:5 12 m Eleocharis olivacea........! 8.3 12 d@ Salsola kali....... ae 8.5 12 | m Scirpus robustus........... 6.8 8.7 ? d Xanthium echinatum....... 10 a d Solidago sempervirens..... 6.5 12 d@d Aster tenuifolius........... 9 11 & Eva GOFATIA «LO. S. eee tents 425 8.5 d Atriplex arenaria.......... 6.5 8.7 d Aster subulatus............ 7.3 9 d Rhus toxicodendron........ 9 12 d Hibiscus moscheutos....... 8 12 US UAT IETS EY oy eee Ace eee 11 12 d Gerardia maritima......... 8 8.7 d Polygonum scandens....... 9 12 || m Distichlis spicata.......... 6.5 8.5 d Ailanthus glandulosa....... 9 12 d Lysimachia terrestris...... 9 ? d Verbascum thapsus......... 9 12 d@ Asclepias incarnata pulch.. 8.3 12 m Agropyron repens.......... 8.8 12 m Agropyron repens.......... 8.7 12 ad Galium claytoni............ 8 12 Solaginella apus........... 9 12 d Oenothera biennis.......... 11 12 Pallavicinia lyellii........ 9 12 d Robinia Pseudo-Acacia..... 9 12 Geax anes AIL, ase cde de 18 12 d Polygonella articulata..... 10 12 m Spartina patens.......... aie 6.5 to 8.7 d Atriplex patula hastata.... Gito 8-5 a@ Sueda maritima............ 6.5 8 d Limonium carolinianum.... 7.3 8.3 5 d Salicornia europxa......... 6.5 7.5 d Plantago decipiens......... 6.3 8.3 m Juncus Gerardi............. URE 8.8 MSIL PUA NANUSE sos cb eace ek. 6.3 8 k (is m Scirpus americanus....... - 6.5 12 m Triglochin maritima....... 6.3 7.5 7.5 m Scirpus robustus........... 6.8 8.7 m Typha angustifolia......... 7.8 12 pas m Distichlis spicata.......... 6.5 8.5 Ce @ Salicornia ambigua........ 6 0 i _|| d@ Spergularia marina........ f 8 7 | 7.25 m Spartina glabra alterniflora.................68. Asieideveisiatalarele inlays oh eG as pate cue eet: eon tow Gro 6 8 ie | d@ Lilzopsis lineata............ ey stavetgialsisiala sal ofNales alaivintre ral citis aie aie’ ap s:ciois alsienic s) sléisiainie’seis's 5.5 6.5 6.5 7 7 7.5 | ea a 7.25 ao... 7.5 7 7 4.5 5 6 4 25 | m Zostera Marina,.......ces-06 TOOL RDO Re ACOCS CONDE OCOCCCBOHOL ONE & aoa e OR ORenCE ie <3 tO} 1.5 mBuppia Maritimiars. vs .cccdsss.vetcce ene nVsiel Selatan Ricinie ele tics ices aiainieisisin er neetecietiia cs era 0 1 Rear e e e e usually grows. The species are given in each belt in the order of prevalence. etic relationship of the forms of each belt. Thus: c= Chlorophycee, p = Phxophycex, r = Rhodophycex, 146 THE RELATION OF PLANTS TO TIDE-LEVELS this is reduced to about 2,250,000 cubic feet, and at a low water of —1-foot, during spring tides, the volume may be only 700,000 cubic feet, or one-sixtieth of that at high water. There is no adequate evidence that these variations in salinity are of con- sequence to the plants found established in the harbor. The low salinity at low water, however, may well be an important factor in preventing other red alge, now occurring in the Outer Harbor, from getting a foothold in the Inner Harbor. Of far more importance are the relatively rapid changes from water of a specific gravity of 1.019 to absolutely fresh water, and the reverse, to which plants growing between tide-lines in the fresh-water tributaries are subjected twice each day. We have already spoken of the algew Hnteromorpha intestinahs, Ilea, and Monostroma as occurring in or near fresh-water tributaries, where at high water they are surrounded by salt water, but, with the fall of the tide, are left with fresh water running over them, often for 8 or 10 hours continuously. The transition from one extreme to the other may, in the case of the small rivulets, occur very suddenly, probably in the course of a very few minutes. This is true because where there is but a small flow from a rivulet it may cause little mingling of the fresh and salt water about the alge until the water has fallen almost to their level. Up to this time the fresh water, being lighter, simply spreads out on top of the salt water and leaves the alge, which may be but an inch or two below, surrounded by salt water. Even in the case of larger streams such as that entering the harbor from the ponds of the New York State Fish Hatchery at 600 south by 720 east, Miss Streeter found that the water at the bottom, surrounding the alge, may change from a specific gravity of 1.014 to one of 1.000 in an hour’s time, with a fall of but 1 foot in the tide. From a careful study of the floras of the between-tides portions of fresh-water tributaries, all about the harbor, it is evident that the rapid changes in salinity of the water must prevent many plants found elsewhere from growing in these ‘areas. On the other hand, the ability of the alge mentioned to withstand these conditions make these areas places of refuge for these alge, where they are free from the competition of other species; Ilea, e. g., for example, covers many square meters of the pebbly bottom of the Creek, between 200 and 500 south, practically to the exclusion of other species, except the inconspicuous diatoms. It must also be recalled that these rivulets have another advantage, perhaps the principal one, in that they form habitats where these more delicate alge are not subject to desiccation during low tide, as they would be elsewhere at the same levels. The salinity of the soil-water on various portions of beach and marsh, both at the same and at different levels, is undoubtedly a factor of very great importance in determining the distribution of plants. Reference has been made in the body of the paper to the fact that Lilea subulata, Scirpus americanus, and S. robustus are found chiefly in soils more or less saturated with fresh water, and to the fact that Iris versicolor, and probably Hibiscus moscheutos, push down to their lowest levels in spots where the soil, though below high-water mark, is saturated by running or seeping fresh water. A series of quantitative determinations of the salinity of the soil-water in various of these habitats has been initiated, but determinations are not yet numerous or complete enough to allow of detailed discussion. The method being used is like that used by Harshberger (1909, TEMPERATURE OF WATER 147 1912) in the study of the New Jersey marshes. It is hoped that the results of these determinations may be presented in a later paper by the junior author of this one. 5. THE TEMPERATURE OF THE WATER. On the subject of the temperature of the water also we have no quantitative results to present. A few measurements of the temperature at the bottom and at the surface of the middle of the Inner Harbor at high tide (of 7.5 feet) were taken in July 1909, which showed a difference of but 1° or 1.5° C. In Miss Streeter’s records made in July, the temperature of the stream at 600 south by 720 east was found to vary from 9° C. at low tide to 18° C. at high water. Itis evident of course, that plants like Zostera, Ruppia, Ulva, etc., which lie on the black, heat-absorbing mud in the sun at low water, must often be heated to 30° or 35° C. or higher, in the summer. When, on the contrary, these plants are exposed at night, their temperature must fall at least to 10° C. or lower, since the air temperature may go down to 8° or lower during the growing season. Just what part the seasonal change of water-temperatures plays directly, in determining the seasonal development of the alge of the bottom, can not yet be stated. It is a well-known fact that the algal flora of a given locality varies markedly from winter to summer. In Section III of this paper it has been pointed out that not only are certain of the characteristic summer forms wanting in April and December, but in the former month, at least, Ulva, one species of Ectocarpus, and Porphyra were far more abundant in the Inlet than they have ever been in the summer. The rockweeds all about the harbor, which in summer bear practically no epiphytes, were found densely coated with filaments of Ulothriaz flacca. In just how far the low temperatures of winter are directly responsible for the abundance of these alge in winter, or whether they may be indirectly responsible by affecting the evaporation, has not yet been ascertained. Possibly, as Warming suggests (1909, p. 151), experimental physiological study may show that the larger proportion of dissolved O and CO, held by the water when cold offers the real explanation of the greater abundance of certain species in winter. The whole subject of the winter activities of marine plants is greatly in need of continuous study, such as has now become possible, with our many well-equipped marine laboratories. V. SUMMARY AND CONCLUSIONS. The Inner Harbor of Cold Spring Harbor has an area of 110 acres at high water. At low tide it has an area of 45 acres, with a maximum depth of 7 feet over an area only 100 feet in diameter. The mean range of tides is 7.75 feet. By the aid of two series of perpendicular range-lines, marked with stakes, the positions of tide-lines, or of plants on the shore or in the harbor, could be accurately determined and recorded. A tide-curve was constructed from read- ings made on a tide-stake, and checked by one made later by a self-recording tide-gage. From this tide-curve the times of submergence and exposure of shore-levels, and thus of plants, were determined. The chief vegetational zones or belts distinguished, with their upper and lower tidal limits, are the following: (1) The plankton, of Diatomacez and Peri- dinew. (2) The bottom vegetation (—5 to +1.5 feet), including the “ enhalid formation ” of Ulva, Enteromorpha, Zostera, and Ruppia; the “ lithophilous benthos ” of Enteromorpha, Ulva, Fucus, Pylaiella, Chondrus, Porphyra, etc., attached to stones and shells, and the epiphytic alge on Zostera and Ulva, chiefly diatoms, Enteromorpha and Ceramium. (3) The mid-littoral belt (1.5 to 6.5 feet). This is the most clearly limited belt about the harbor. It in- cludes a Spartina glabra association on sloping shores and a rockweed associa- tion, of Fucus, Ascophyllum, and Bostrychia, on the wharves. (4) The upper littoral belt ( 6.5 to 8 feet), which has a more varied vegetation, including asso- ciations of felted filamentous alge, of Spartina patens, of Salicornia, of Sueda, and of Scirpus, each either pure or mixed with members of one or more of the other associations mentioned, or with more or less scattered individuals of Scir- pus, Distichlis, Atriplex, Limoniwm, or Spergularta. (5) The supra-littoral belt (8 to 12 feet). ‘This is less clearly defined and more varied in make-up than the other belts. It includes associations composed of Ammophila, Solidago, Salsola, Cakile, and Lathyrus, of Scwrpus americanus and 8S. robustus, of Aspidvum thelypteris, and also includes more scattered and mixed groups of Asclepias, Aster, Baccharis, and Hibiscus, besides many upland plants. The external environmental factors which influence the distribution of plants in this harbor are: substratum, water-currents, changes in water-level with the tides, salinity, and temperature of the water. The substrata, aside from living plants, vary from fine silt, humus, or peat, to sand, gravel, rocks, and logs. The plant-covering at any level differs with the type of substratum, depending largely on the drainage possible. The soft, undrained mud of the very bottom of the harbor bears only Zostera, Ruppia, and anchored plants of Ulva and Enteromorpha. Other plants of the bottom, all of . them alge, require a firm substratum, as stone, a shell, or another plant, for attachment. ‘T’he physical character of the soil greatly affects the rate of drainage of salt water from shore between the tide-lines and of fresh water from the upper levels, and thus determines the type of vegetation growing on them. For example, where the soil of the Spit above the 6-foot level is gravelly 148 SUMMARY AND CONCLUSIONS 149 and well-drained, Spartina glabra grows but little above this and is succeeded by Salicornia and Sueda, while on the peaty soil of flatter parts of the shore S. glabra may extend up to the 7.5-foot level and there be succeeded by Spartina patens or Distichlis. If fresh water is present in the fine soil of the upper levels, Spartina glabra is succeeded by Scirpus americanus and sometimes mingled with it up to the 8-foot level. On the Marsh the character of the vegetation of the surface is correlated with the local thickness of the peat above the underlying gravel. The effects of water-currents on the distribution of plants are exercised by the dissemination of spores and seeds and by the breaking off and transportation of the shoots of Zostera, and of alge like Ulva, Enteromorpha, Fucus, etc., which persist and grow in their new lodging-places. In other cases water-currents, by mechanically injuring the plants or by determining the character of the sub- stratum, may favor or retard the further extension of a species. On the other hand, the rapid movement of the water is an evident advantage to some species, perhaps by increasing the interchange of material between the plant and the surrounding water, and possibly also by injuring competitors. Thus Zostera, Cladophora, Pylaella, Chondrus, Polysiphonia, Porphyra, etc., are most abun- dant in or beside the rapid tidal current of the Inlet. Jlea, Monostroma, and Pylatella likewise are abundant only in the rapidly flowing Creek entering the south end of the harbor. A careful study of the vertical distribution of the littoral plants about this harbor shows that this depends primarily and very definitely on the relative time of their submergence and emergence with the rise and fall of the tide. Moreover, the vertical range of littoral species is strictly, sometimes very narrowly, limited. There are no species here, except two or three alge, that are distributed “between tide-marks” (1. e., from low water up to high water), as is so often reported. The nearest approach to this range found for any seed plant is that of Spartina glabra, whose vertical range of 5 feet (from 1.5 to 6.5 feet above mean low water) lies midway between the limits of the average (8-foot) tide. The range of this salt reed-grass covers but five-eighths of the mean tide- range and only half the range of many spring tides of the growing season (10 to 11 feet). This Spartina never gets below 1.5 feet and only in exceptionally moist and shaded areas does it grow at any appreciable distance above 6.5 feet. The alga Fucus ranges from just below mean low water up to 7.25 feet and Enteromorpha intestinalis has a similar range on shores where fresh-water rivulets flow in over the upper beach. The other seed plants of the shore range down to but 1.5 or 2 feet below mean high-water level (7.75 feet), with the exception of Lilgopsis, which is found between 5 and 6.5 feet. Zostera and Ruppia range upward for only 1 or 1.5 feet above mean low water. The essential feature, for our purpose, of the tidal oscillation of water-level is the relative times of submergence and exposure experienced by the various shore-plants. For the sake of comparison this relation is most significantly expressed in a fraction for the upper limit and one for the lower limit of distri- bution of each species (p. 135). The influence of this change in water-level on the plant is effected through differences, at different levels, in evaporation rate ; in aeration; in salinity of soil-water at higher levels; in exposure to rain and in light supply. It seems evident, for example, that Spartina glabra 150 THE RELATION OF PLANTS TO TIDE-LEVELS and the rockweeds do not grow at levels above 6.5 feet, because they can not endure a greater evaporation than that experienced here. Zostera and many alge for the same reason are confined to levels below mean low water, except where washed by tidal streams during low tide. It seems probable also that the too brilliant light or the exposure to rains during low tide prevents certain algee from growing above mean low water. On the other hand, certain plants are stopped in their spread downward because they can not endure the longer sub- mergence, with the lessened aeration and light supply, at lower levels. Spartina glabra, for example, as has been shown experimentally, is undble to persist more than a few months at levels even slightly below 1.5 feet. The rockweeds also seem unable to persist below the level just mentioned in the usually quiet and turbid water of the Inner Harbor. In the clearer, rapidly moving water of the Inlet, however, and especially in that of the Outer Harbor and Long Island Sound, Fucus grows a foot or more below mean low water. The degree of salinity clearly determines the horizontal distribution of many plants in this harbor. For example, one series of alge, chiefly Chlorophycee, occur only in the less saline south end of the harbor, where they are flooded with fresh water for from 2 to 10 hours each tide. On the other hand, the majority of the Floridee found here grow in the channel to the Outer Harbor, where the water is most saline. In the list of plants of the harbor (pp. 151 to 161), there are indicated for each species the physical characteristics of the habitat which are believed to be concerned with its distribution. In but relatively few instances has the connec- tion between the distribution and external conditions been experimentally shown. Though the attempt has been made in the body of this paper to suggest the external factors determining the distribution of each common species, this must be regarded as a suggestion of the elements entering into the problem rather than as a statement of its definite solution. It is believed that the determination of the relative time of submergence and exposure of a plant at its upper and its lower limit in this harbor, where the range of tide is about 8 feet, will make it possible to predict the vertical range of the same species in any other region, if the range of the tide is known. That is, the vertical range of a littoral plant is exactly proportional to the range of the tide. In this study chief attention is devoted to determining and recording as accurately as possible the present distribution of the plants of this harbor in relation to tide-levels, salinity, and soils. Little has been said of the succession in time of the formations occurring at different levels on the shore. It is believed that this historical aspect of the problem can be solved more satis- factorily by the comparison of the vegetation that will exist here some years hence with that which is here recorded. VI. LIST OF VASCULAR PLANTS OF THE BOTTOM AND SHORE, WITH VERTICAL RANGE AND THE PHYSICAL CHAR- ACTERISTICS OF THE HABITAT OF EACH. EXPLANATION OF TABLE F. The data included in Table F are those listed immediately below, and they are indicated for each species found below the 12-foot level as far as known. Each characteristic of the plant or its environment is indicated in the proper column by a word or phrase, or, for the sake of brevity, by the symbol indicated in this list of data. The 12 data noted for each species in Table F are arranged, in a horizontal line, in the following order: if Symbol: This is used to indicate the species on charts and plates. II. Name of the species: The nomenclature in the case of ferns and seed plants is that of Gray’s New Manual of Botany, seventh edition. III. Habitat and persistence of the species: 1. Annual herb: an. 2. Biennial herb: bi. 3. Perennial herb: per. 4. Shrub or woody vine: sb. 5. Tree: tr. TV. Density of stand or frequency of individuals of the species: A dash separating two symbols indicates that the density varies from the first to the second type. 1. Pure stand: pure. This is used only where a species may cover from several square decimeters to, in other cases (e. g., of larger species), many square meters, with dozens, scores, or hundreds of individuals. 2. Mixed: preponderatingly, or nearly equally, with another species. This will be indicated by the use of the symbol for the second species thus: + Sp. means that the species in question has Spartina patens mixed with it. 3. Seattered: among a second species and less abundantly than it; e. g., Sp. + indicates that the species is mingled with Spartina patens and is outnumbered by the latter. 4. Grouped or clumped: gpd. 5. Seattered, occasional, or isolated: oc. V. Substratum: Of the 9 substrata listed the last 4 will be used only in the list of alge. 1. Mud: md. This is soft, saturated soil, usually sparsely covered. 2. Humus: hu. Used for dry or moist humus-containing soils, except the peaty soil on the Marsh. It includes the very sandy humus of the top of the Spit. 3. Peat: pt. This includes soils, wet or moist, chiefly of organic origin, and bound together by dead and living roots and rhizomes. 4. Sand: sd. This may be dry, as at high levels on the Spit, or nearly saturated when between tide-marks. . Gravel: gv. Chiefly near high-water level. Rock: rk. This includes larger pebbles, the stones of the wharves, and boulders of the bottom or shore. . Shells: sh. The shells of living and dead lamelli branch and gastero- pods. . Wood: wd. Stakes, the logs of wharves, and sunken trunks or stakes on the bottom. . Living substratum: Chiefly Mytilus edulis among animals and Zostera and Spartina glabra among plants. Less commonly Ulva and the stouter red algsze may serve as substrata for certain diatoms and blue- green alge. Thus, e. g., ep./Z. means epiphytic on Zostera. 151 ie) co “a 2 Ol 152 THE RELATION OF PLANTS TO TIDE-LEVELS VI. Salinity of the soil water during the growing season: It may be more saline at levels above 8 feet in winter, due to storms, or, even in the growing season, the salinity may temporarily become somewhat greater near the high-water mark from the concentration due to evapo- ration. It may again be less saline at these upper levels after rains. 1. Salt: sa. By this is meant water of the density of that usually found at the surface of the harbor at high tide, which has a specific gravity of 1.019. 2. Brackish: br. Distinctly less dense than the above. 3. Fresh: fr. VII. Light demands: That is, the light conditions under which the species usually grows. 1. Sun plants: su. 2. Shade plants: sd. VIII. Upper limit of vertical distribution: The average upper limit of distribution of the species is given in feet above mean low water (indicated by the plus sign) or below mean low water (indicated by the minus sign). Where 12 feet + is used in this column it indicates that the plant may grow at this level, which is the highest level reached by winter tides, and at any level above this. That is, the plant is not confined to sea-coasts. In all other cases the upper limit given is the highest level at which the plant has been found about this harbor. Where but few individuals have been seen, and so the possible vertical range could not be determined with certainty, the one level at which it was found is indicated in this column and the column for the lower limit is left vacant. IX. Lower limit of vertical distribution: The average recorded lower limit of dis- tribution is given in feet, above or below mean low-water level for the soil upon which the plant grows at this limit. The extremes of distribution are given in Section III. The plus and minus signs are used as in column VIII to indicate levels above and below. X. Emergence or exposure: This is given, in the average number of hours per lunar day, for the soil which bears the plants at the upper limit of the species. It thus indicates the greatest average exposure endured by any plants of the species, aside from the few exceptional indi- viduals that may occur at slightly higher levels in habitats where the shade or moisture conditions are especially favorable. The data for emergence are taken from Table A (p. 135). Additional infor- mation concerning the occasional exposure of low levels and the duration of continuous exposure of higher levels may be obtained from Tables B and C (p. 136). The exposures during the hours of daylight may be seen from Table D, on page 142. Of course, the exposure of the soil on which a plant is growing indicates merely the exposure of the shoot above the soil. The subterranean por- tions are still immersed in a soil that may be practically satu- rated with salt water, e. g., Spartina glabra, or with fresh water, e. g., Sagittaria latifolia. XI. Submergence: This is given for the soil on which the plant grows at the usual lower limit of distribution of the species, as indicated in column IX of Table F. The submergence given thus indicates in hours per lunar day of 24.9 hours, the average submergence endured by the lowest plants of the species in question during the growing season. The duration of submergence here given is taken from Table A (p. 185) and is calculated in the manner mentioned in the explana- tion of that table. The number of submergences per month or per growing season for plants near the high-water level, or the duration of continuous submergence of plants near mean low water, can be learned from Table B and Table C (p. 136). The occasional sub- mergence of levels between 9 feet and 10 feet by storm tides is sug- gested in the cases of plants growing at these levels. Only winter — storm tides ever cover levels much above 10 feet. XII. Ratio of emergence to submergence: This is given for plants at the lower limit of vertical distribution of the species and at the upper limit. The two figures thus indicate the range in conditions, so far as the latter are affected by the tides, under which each species shows itself capable of growing here at Cold Spring Harbor. 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"YM013 Jo -4s1s.ia ; BVEvOG iad painpua | iad paasnpua| samo | reddy | -qns jo be dete gh Ayisued 10 RIMEN SUTMOIZ BULINP) gnuaZ1auiqns| aoueS.10ura syrurpeg q1qeH “ q rut wove cseUrgne ISBIIAV aSvIIAV 0} sdUaZIEWS Jo o1jey ‘IX ».4 ‘x! ‘TITA | “ITA ‘IA “A “AI ‘III eLt ‘ponulju0g—'saraads yona fo zoRIQDY 2Y2 YRIM ‘sazhydoijpYy2 [0 1817 —"*s) AIAVL DIATOMACE 161 any alga growing between tide-marks may be washed by fresh water during heavy rains at low tide. The stand of any given alga may be pure over several square centimeters, a few decimeters, or, in some species, over some square meters. The vast majority of species, however, are mingled more or less abundantly with others, or occur sparsely, or even rarely as individuals, attached or free, often with no others of their kind within a distance of many meters. The latter is often true, e. g., of Agardhiella, Gracilaria, Porphyra, etc. Where but one or a few collections of a species have been made, and all at one level, this level is given under “ upper limit.” DIATOMACE. Besides the diatoms mentioned in Table G, a number of other species were identified by Dr. Albert Mann, in collections made on November 30, 1912, from the 3-foot level on two stakes in the middle of the harbor and from shells in the Inlet near the 1-foot level. They were not sought elsewhere and therefore their general distribution can not be given, as their colonies are not large enough to be conspicuous among the other alge of their habitats. The following include all the diatoms thus far identified from the Inner Harbor: Achnanthes brevipes Ag. Navicula alternans Schum. hauckii Grun. grevillei (Ag.) Cleve. longipes Ag. Kennedyi W. S. Actinoptychus splendens (Shad.) lyra Ebr. Ralfs. marina Ralfs. Amphora eulensteinii Grun. smithii Breb. Biddulphia aurita ,Lyngb.) Bred. Nitzschia acuminata W. S. Grun. Cocconeis scutellum Ehrb. longissima (Breb.) Ralfs. Coscinodiscus asteromphalus Ehrb. panduriformis (Greg.) decrescens Grun. Grun. excentricus Ehrb. paradoxa (Gmel.) Grun. radiatus Ehrb. sigma W. S. Cyclotella striata (Kg.) Grun. Pleurosigma angulatum W. S. Fragillaria brevistriata Grun. balticum W. S. Fragillaria sp. distortum W. S. Gomphonema curvatum Kg. intermedium W. S. Grammatophora marina Kg. Podosira subtilis (Bail) Mann. Licmophora tincta (Ag.) Grun. Synedra affinis. Lithodesmium undulatum Ehrb. Melosira borrei Grev. nummuloides (Bory.) Ag. VII. LITERATURE REFERRED TO. BAKER, S. M. 1909. The causes of the Zoning of Brown Seaweeds on the Seashore. New Phytologist, vim, p. 196, and 1x, p. 54, 1910. BERTHOLD, G. 1883. Ueber die Verteilung der Algen im Golf v. Neapel, etc. Mitt. aus den zool. Stat. zu Neapel, 3, p. 393. CLEMENTS, F. E. 1905. Research Methods in Ecology. Lincoln, 1905. CoLtutins, F. S. 1905. Phycological Notes of Isaac Holden. Rhodora, 7, pp. 168-172, 222-243. Corton, A.D. 1911. On the Growth of Ulva latissima in Excessive Quantity. Royal Comm. Sewage Disposal, Report 7, App. tv, p. 121. CowLes, H.C. 1899. The Ecological Relations of the Sand Dunes of Lake Michigan. Bot. Gaz., 27, p. 115. Darwin, G. 1910. Tides. Encyclopedia Brittanica, 11th edit., vol. xxv1, p. 940. Davis, B. M. 1913. Bull. Bureau of Fisheries, 31, 1911, Washington, D. C. Davis, C. A. 1910. Salt Marsh Formation near Boston and its Significance. Eco- nomic Geology, 5, p. 631. FARLOw, W. G. 1881. Marine Alge of New England. Report of U. S. Comm. Fish and Fisheries, 1879. FULLER, G. D. 1912. Evaporation and the Stratification of Vegetation. Bot Gaz., 54, p. 424. GRAVES, A. H. 1908. The Morphology of Ruppia maritima. Trans. Conn. Acad. Sc., 14, p. 59. HARSHBERGER, J. W. 1909. The Vegetation of the Salt Marshes, etc., of Northern Coastal New Jersey. Proc. Acad. Nat. Sci. Phila., p. 373. 1912. An Hydrometric investigation of the influence of Sea Water on the Distribution of Salt Marsh and Estuarine Plants. Proc. Amer. Phil. Soc., 50, p. 457. JOHNSON, D. W. 1913. Botanical Phomena and the Problem of Recent Coastal Sub- sidence. Bot. Gaz., 56, p. 449. KEARNEY, T. H. 1904. Are Plants of Sea Beaches and Dunes True Halophytes? Bot. Gaz., 37, p. 424. KJELLMAN, F. R. 1877. Ueber die Algenvegetation des Murmanschen Meeres an der Westktiste von Nowaja Semlja und Wajgatsch. Nova Acta Regie Societat. Scient. Upsaliensis, Volumen Extra Ordinem, 1877. 1878. Ueber Algenregionen u. Algenformationen im Ostlichen Skager Rack. Bihang til Kongl. Vetensk. Ak. Hdl., 5, No. 6. Lewis, I. F. 1914. The Seasonal Life Cycle of some Red Alge at Woods Hole. Plant World, 17, p. 31. Letts, E. A., and E. H. RicHarps. 1911. On Green Seaweeds in relation to the Pol- lution of the Water in which they occur. Roy. Comm. Sewage Disposal, Report 7, App. 1, p. 72. LIVINGSTON, B. E. 1911. A Study of the Relation between Summer Evaporation Intensity and Centers of Plant Distribution. Plant World, 14, p. 205. 1906. Carnegie Inst. Wash. Pub. 50. LORENZ, J. R. 1863. Physicalische Verhdltnisse und Verteilung d. Organismen im Quarnerischen Golfe. Vienna, 1863. OLIVER, F. W. 1912. The Shingle Beach as a Plant Habitat. New Phytol., 11, p. 73. OLTMANNS, F. 1905. Morphologie u. Biologie der Algen, vol. m1, Jena. OSTENFELD, C. H. 1908. On the Ecology and Distribution of the Grass Wrack (Zos- tera marina) in Danish Waters. Report of the Danish Biological Station to the Board of Agriculture, xvi, p. 1. TITTMAN, O. H. 1910. Tide Tables for the Year 1911. U.S. Coast and Geodetic Sur- vey, Washington, 1910. TRANSEAU, E. N. 1908. The Relation of Plant Societies to Evaporation. Bot. Gaz., 45, p. 217. 1913. The Vegetation of Cold Spring Harbor, Long Island. I. The Littoral Successions. Plant World, 16, p. 189. WARMING, E. 1906. Dansk Plantevaekst. 1 Strandvegetation. Copenhagen and Christiania. . 1909. Qicology of Plants. Oxford. Yapp, R.H. 1909. On Stratification in the Vegetation of a Marsh, and Its Relations to Evaporation and Temperature. Ann. of Bot., 23, p. 275. 162 THE RELATION OF PLANTS TO TIDE-LEVELS A STUDY OF FACTORS AFFECTING THE DISTRIBUTION OF MARINE. PLANTS BY DUNCAN S. JOHNSON AND HARLAN H. YORK WASHINGTON, D. C. PUBLISHED BY THE CARNEGIE INSTITUTION OF WASHINGTON 1915 & Se i poy | Value fi io) Ohl Ae eat Atavus AN Ay ay PERL hy he so i 3) sii) | Dee we Lie ee Wt fi CNET tar Hen YY i pe) Hy UNIVERSITY OF ILLINOIS-URBANA tt Siecat Mm 581.15J63R co01 un THE RELATION OF PLANTS TO TIDE-LEVELS$WA WANN ys | i 3.0112 009926350 “ pried : ’ t laa ’ : f ‘ 4 a f t ia iepy ' Pa eee a etsy} oye ; wane } se at a ‘i at F Sane POH OS Fain a ‘ta tee ea Re i ; 4% ; $ih id ; Wee y : 3 178, . Seether dicl edie F) ‘iy jd Hoprenat argh er gee Ree abbey bahay jaged ripen an ' i Beye ded raen Wed Heae | i i ) Hep hed ' . 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