33 r. S. DEPARTMENT OF AGRICULTURE, BUREAU OF PLANT INDUSTRY BULLETINS. 193. li. T. GALLOWAY, I hi*) ■■( Bureau. EXPERIMENTS IN BLUEBERRY CULTURE. BY FREDERICK Y. GOV1LLE, Botanist in Charge op Taxonomic and Range In Issued November 1">. 1910. r OOCUMpNTskfaj U.S. OEPOSITORY WASHINGTON: GOVERNMENT PRINTING OFFICE. 1910. BULLETINS OF THE BUREAU OF PLANT INDUSTRY. Th'' scientific and technical publications of the Bureau of riant Industry, which was organized July 1, 1901, are issued in a single scries of bulletins, a list of which follows. Attention is directed to the fact that the publications in this series are not for general distribution. The Superintendent of Documents, Government I'rinting Office. Washington, 1). ('.. is authorized by law to sell them at cost, and to him all applications for these bul- letins should be made, accompanied by a postal money order for the required amount or by cash. Numbers omitted from this list can not be furnished. No. 2. Spermatogenesis and Fecundation of Zamia. 1901. Price. 20 cents. .'!. Macaroni Wheats. 1901. Price, 20 cents-. 4. Range Improvement in Arizona. Idol. Price, 10 cents. X. A Collection of Fungi Prepared for Distribution. 1!)02. Price, 10 cents. !). The North American Species of Spartina. 1902. Price. 10 cents. Id. Records' of Seed Distribution, etc. 1902, Price, 10 cents. 11. Johnson Grass! 1902. Price, 10 cents. 13. Range Improvement in Central Texas. 1902. Price, 10 cents. 14. The Decay of Timber and Method's of Preventing It. 1902, Price, 55 cents. 1.">. Forage Conditions on Northern Border of Great Basin. 1902. Price, 15 cents. 17. Some Diseases .it the Cowpea. 1902. Price. 10 cents. 20. .Manufacture of Semolina and Macaroni. 1902. Price, 15 cents. 22. Injurious Effects of Premature Pollination. 1902. Price, 10 cents. 23. Berseem : The Great Forage and Soiling Crop of Nile Valley. 1902. Price, 15 cents. 24. Fnfennented Grape Must. 1902. Price, lo cents. 25. Miscellaneous Papers. 19(1.",. Price, 15 cents. 27. Letters on Agriculture in the West Indies. Spain, etc. 1902. Price, 10 cents. 20. Tlie Effect of Black-Rot on Turnips. 1903. Price. 15 cents. 31. Cultivated Fotage Crops of the Northwestern States. 1902. Price, 10 ceuts. 32.. A Disease of the White Ash. 1903. Price. II) cents. 33. North American Specii s of Leptochloa'i 1903. Price. 15 cents. 35. Recent Foreign Explorations. 1903. Price, 15 cents. HO. The "Bluing"' of the Western Yellow Pine. etc-. 1903. Price. 30 cents. 37. Formation of Spores in Sporangia of Rhizopus Nigricans, etc. 1903. Price, 15 ceuts. MS. Forage Conditions in Eastern Washington, etc. 1903. Price, 15 cents. :;i). The Propagation of the Faster Lily from Seed." 1903. Price, 10 ceuts. 11. The Commercial Grading of Com. 1903. Price, in cents. 42. Three New Plant Introductions from Japan. ""3.903. Price, 10 ceuts. 47. The Description of Wheat Varieties. 1903. Price, id cents. 48. The Apple in Cold Storage. 1903. Price. 15 cents. 40. Culture of the Central American Rubber Trees 1903. Price. 25 cents. 50. Wild Rice: its Cses and Propagation. loo::. Price, 10 cents. 51. .Miscellaneous Papers. 1905. Price. 5 cents. 54. Persian Gulf Dates.. 1903. Price. 10 cents. 59. Pasture, Meadow, and Forage Crops in Nebraska. 1904. Price, 10 cents. 60. A Soft Rot of the Calla Lily. 1004. Price, 10 .-cuts. 01. The Avocado in Florida. 1004. Price. 5 cents. 62. Notes on Egyptian Agriculture. 1904. Price, 10 cents. 67. Range Investigations in Arizona. 1904. Price. 15 cents. 68. North American Species of Agrostis. 1905. Price, 10 cents'. 00. American Varieties of Lettuce. 1904: Price. 15 cents. 70. The Commercial Status of Durum Wheat. 1004. Price. 10 cents. 71. Soil Inoculation for Legumes. 1005. Price. 15 cents. 72. Miscellaneous Papers. 1005. Price. 5 cents. 7:!. The Development of Single-* lerm P.eet Seed, 1905. Price. 10 cents. 74. Prickly Pear and Other Cacti as Food for Stock. 1905. Price, 5 cents. 75. Range' Management in the Slate of Washington. 1905. Price. 5 cents. 76. Copper as tin Algicide and Disinfectant in Water Supplies. 1905. Price, 5 cents. 77. The Avocado : A Salad Fruit from the Tropics. 1005. Price. 5 ceuts. 70. Variability of Wheat Varieties in Resistance to Toxic Salts, p.iij.j. Price, 5 cents. so. Agricultural Explorations in Algeria. 1-9051 Price, lo cents. 81. Evolution of Cellular Structures: 1905. Price. 5 cents. .XL'. Crass Lands of I lie South Alaska Coast. 1905. Price, 10 cenls. 83. The Vitality of Buried Seeds. 1905. Price. 5 cents. 84. The Seeds of the Bluegrasses. 1005. Price, 5 cents. 85. Principles of Musbroom Crowing and Spawn Making. 1905. Price, 10 cents. Si;. Agriculture without Irrigation in the Sahara Desert. 1905. Price. 5 cents. 88 Weevil Resisting Ada pi al ions of the Cotton Plant. 1900. Price. 10 cents. SO. Wild Medicinal Plants of (be 1 idled States. 1906. Price, 5 cents. 00. Miscellaneous Papers, 1006. Price. 5 cents. 01. Varieties of Tobacco Seed I list ribnted. etc. 1900. Price. 5 cents. 94. farm Practice with Forage Crops in Western Oregon, etc. 1900. Price, 10 cents. 95. A New Type of Red Clover. 1906. Price. 10 cents, oo. Tobacco Breeding. 1907: Price, 15 cents. 97. Seeds and Plants Imported. Inventory No. 1 1 . 1907. Price, 15 cents. 0,s. Soy Lean Varieties. 1907. Price. 15 cenls. oo. Quick Melboii for Determination of Moisture in Grain. 1907. Price, 5 cents, loi. Contents of and Index to Bulletins Nos: I to loo. 100,. Price, 15 cents. 102. Miscellaneous Papers. 1007. Price. 15 cents. 103. Dry farming in the Grout Basin. 1907. Price, 10 cents. 104. The I'se of Foldspalhic Rocks as Fertilizers. 1007. Price, 5 cents. 105. Relation of Composition of Leaf to Burning of Tobacco. 1907. Price. 10 cents. 106. Seeds and Plants Imported. Inventory No. 12. 1907. Price, 15 cenls. [Continued on page 3 of cover.] 1 9:; U. S. DEPARTMENT ( >F AGRIC1 fLTURE, BUREAU OF PLANT INDUSTRY BULLETIN NO. 193. B. I GA1 LOWAY, Chief qf Bureau. EXPERIMENTS IN l!LI LltllltltY CULTURE. FREDERICK V. COVILLE, Botanist in Charge of Taxon< >mi« vnd Range Investigations. [SSUBD \< IVEMBKR 15, 1910. WASHINGTON: GOVERNMENT PRINTING < >l I ! C E. L910. BUREAU OF PLANT INDUSTRY. 193 2 Chief of Bureau, Bevekly T. Galloway. Assistant Chief of Bureau, G. Harold Powell. Editor, J. E. Rockwell. Chief Clerk, James E. Jones. Taxonomic and Range Investigations. scientific staff. Frederick V. Coville, Botanist in Charge. A. S. Hitchcock, Systematic Agrostologist. W. F. Wight, Botanist. A. II. Moore and P. L. Ricker, Assistant Botanists. W. E. Safford, Assistant Curator. Agnes Chase. Assistant. E. L. Greene, Expert. LETTER OF TRANSMITTAL. U. S. Depaei \h \ t of Agriculti re, Bi reai or Plant I ndi stry, < )i i H e of the Chief, Washington, IK C.,July 19, 1910. Sib: I have the honor to transmit herewith and to recommend for publication as Bulletin No. L93 of the series of this Bureau a manu- script by Mr. Frederick V. Coville, Botanist in Charge of Taxonomic and Range Investigations, entitled " Experiments in Blueberry Cul- ture." Mr. Coville has found by experiment how blueberries differ from ordinary plants in their method of nutrition and in their soil requirements, and by means of this knowledge he has worked out a system of pot culture under which these plants attain a development beyond all previous expectations. There is good prospect that the application of the knowledge thus gained will establish the blue- berry in field culture and that ultimately improved varieties of these plants will be grown successfully on a commercial scale. A particularly interesting and significant feature of these experi- ments is the light they shed on the possible utilization of the natu- rally acid lands that occupy extensive area- in the eastern United States. These land- are generally valued at a low price, and the chief expense involved in their utilization for ordinary agricultural crops is the cost of correcting their acidity and it- effects by limine-. fertilizing, ami cultural manipulation. The question presents itself, - May we not i v effectively utilize such land.- by growing on them crops which, like the blueberry, thrive in acid soil-? '" Some of the experimental methods and equipment utilized by Mr. Coville are commended to other plant experimenters, especially the f darkened and drained glass pots for the intimate observation of the behavior of root-, and the plunging of pots in moist .-and to maintain equable moisture and aeration conditions. Respectfully, W VI. A . T VYI.OK. Acting Ck'u i of Bun (10) Aeration conditions satisfactory for the swamp blueberry are prevalent in s Is 36 (11) Aeration condition- satisfactory for the swamp blueberry are found in drained fibrous peat 37 deration conditions satisfactory for the swamp blueberry are found in masses of live, moist, hut nol submerged, sphagnum.. 38 Peculiarities of nutrition 40 13) The swamp is devoid of root hairs, tic minuti through which the ordinary planl ulture absorb their moisture and f 1 40 (14) Tlr of healthy plant- of the swamp blueberry are in- habited by a fungus, of the sort known technically as an endo- trophic mycorrhiza 42 ( 15) The mycorrhiza] fungus of the swamp blueberry appears to have no injurious effect, hut rather a beneficial effect, upon the blueberry plant 44 The acid peaty soils in which the swamp blueberry thrives are deficient in "available" nitrogen, although containing lar^e amount- of "nonavailable" nitrogen 45 (17) The deficienc} oi available nitrogen in the acid peaty -oil in which the swamp blueberry grows besl is d ie to tl e inability of the nitrifying ba< teria to thrive in such a -oil because of it- acidity 46 193 CONTENTS. Peculiarities of growth in the blueberry plant- Peculiarities of nutrition — Continued . -Continued. (18 (19 A method of (20 (21 (22 (23 (24 (25 (26 (27 (28 (29 (30 (31 (32 (33 (34 (35 (36 l!.:; Page. From the e\ idence at hand the presumption is that the mycor- rliizal fungus of the swamp blueberry transforms the nonavail- able nitrogen of peaty soils into a form of nitrogen available for the nourishment of the blueberry plant 48 It is possible that the mycorrhizal fungus of the swamp blue- berry transforms the free nitrogen of the atmosphere into a form of nitrogen suited to the use of the blueberry plant 48 pot culture 51 Seeds of the swamp blueberry sown in August from fresh berries germinate in about 5 weeks 51 The seedlings are first transplanted at the age of about 6 weeks, when they are approaching an inch in height 54 When about 10 weeks old and nearly 2 inches in height the seedlings 1 legin to send out basal branches 57 When the seedlings are about 4 months old and about 3 inches in height the growth of the original stem terminates 58 When the plants are about 5 months old and 4 to 6 inches in height they are potted in 4-inch pots in the best peat or prat mixture 59 Blueberry plants potted in peat may be made to grow more rap- idly if they are watered occasionally during the growing season with water from a manure pit 62 Pots containing blueberry plants should be plunged in sand or other material that will furnish constant moisture and gi ol aeration 65 Plants of the swamp blueberry sometimes lay down flowering buds at the age of 7 months 67 In the spring after the danger of frost was past the plants were repotted and placed out of doors, in half shade, plunged in sand 67 By the use of the cultural methods already described, seedlings of the swamp blueberry have been grown into robusl plants of a maximum heighl of 27 inches at 12 months from germi- nation 68 The (lowering buds of the blueberry are produced by the trans- formation of dormant leaf buds in the latter pari of the season. 71 At the end of their first year 70 per cent of the blueberry plants had laid down flowering buds for the next spring's blossoming. 73 Plants of the swamp blueberry are exceedingly hardy and pass the winter in good condition outdoors when the soil is covered merely with an oak-leaf mulch, but when not exposed to out- door ei i ml it ions they do not begin their growth in spring in a normal manner 74 Dormant plants make their early spring twig growth before new roots begin to develop 76 Unless pollinated by an outside agency, such as insects, the Sowers produce little or no fruit 76 The f i nit matures aboul 2 months after the flowering 78 So far as observed, the swamp blueberry when grown in acid soils is little subject to fungous diseases or insect pests 79 C0N1 ENTS. 7 Improvement and propagation 80 .•hi plant of the swainp blueberry seedlings, the culture of which has been described, bore berries over hall' an inch in diameter 80 There is every reason to believe that the blueberry can bi improved by breeding and l>y selection 82 The swamp blueberry bas been propagated by grafting, by bud- ding, by layering, by twig cuttings, and by root cuttings 83 sirable method of propagating the swamp blueberry is by cuttings 84 Field culture 36 ; leriments have been begun in the field culture of the swamp blueberry ^ 86 Conclusion 38 Index 9] ILLUSTRATIONS PLATES. Page Plate I. Fig. 1. — Rool growth of a blueberry plant in clay mulched with leavi 2 Ri o1 growth of a blueberry plant in peat lM 1 1. Blueberry Beedlings in prat and leaf mold 26 III. Fig I Formation of kalmia prat, top layer. Fig. 2. — Formation of kalmia prat, second layer IV. Fig. L. — Formation of kalmia peat, third layer. Fig. 2. Formation of kalmia peat, fourth layer 34 Y. Fig. 1. — Formation of kalmia peat, fifth layer. Fie. 2. — Formation of Kalmia pi 'at, sixth lay it 34 VI. Fig. 1. — Swamp blueberries from the parent bush of the seedlings < 1908. Fig. 2. Seeds of the swamp blueberry 52 VII. Blueberry seedling four and a half months old 60 VIII. Cold frames containing one-year-old blueberry seedlings 68 1 \. Large one-year-old seedlings of the swamp blueberry 70 X. Fig. 1. Flowering buds and leaf buds on blueberry twigs. Fig. 2. Flowering buds <>n a blueberry cutting. Fig. :>. — Flowering buds on blueberr} cuttings ~i. XI. Yearling blueberry plant with -1'-' flowering buds 74 XII. I"i(.. l. Blueberry plant which wan wintered indoors beginning growth in the spring. Fig. 2. — Blueberry plant which was win- ten. 1 outdoors beginning growth in the sprint: 76 \1II I : i Blueberry plant which was wintered indoors continuing growth in the spring. Fig. 2. — Blueberry plant which was win- tered outdoors continuing growth in the spring 7'> XIV. Irregular flowering ol a blueberry plant wintered indoors 78 X V. I Jerry ripened on a blueberry seedling at the age of 19 months s " XVI. Fig. l. Grafted blueberry. Fig. -. Blueberry seedling success- fully budded 84 XVII. Blueberry plants from twig cuttings 86 XVIII. Blueberry plant from a twig cutting ^ [•EXT lie lie i . Rose cutting in rich garden soil 16 Rose cutting in peat mixture Alfalfa seedlings in rich garden soil 17 i Alfalfa seedlings in peal mixture 17 5 Blueberr) seedling in rich garden soil 18 ng in peat mixture 18 7. Blueberry seedling in peat mixture limed 23 - Blu< berry seedling in peat mixture tin lime. I 23 9. Blueberry seedling fed with alkaline nutrient solution 10. Blueberry seedling fed with acid nutrient solution :il 193 ., 10 ILLUSTRATIONS. Page. Fig. 11. Root of a wheat plant, showing the root hairs 40 12. Portion of a wheat root, with root hairs 40 13. Tip of the root hair of a wheat plant 40 14. Root of a blueberry plant 41 15. Root of a blueberry plant, enlarged 41 16. Blueberry rootlet 41 17. Mycorrhizal fungus of a blueberry plant densely crowded in two epidermal cells of the root 43 18. Mycorrhizal fungus of Kalmia latifolia in an epidermal cell of the root. 44 19. Section of a blueberry seed 53 20. Blueberry seedlings in the cotyledon stage 53 21. Blueberry seedling about 6 weeks old, with five foliage leaves 54 22. Normal tip of stem in a blueberry seedling 57 23. Bract and young leaf at the end of the original stem in a blueberry seedling 58 24. Blueberry seedling with diffuse type of branching 59 25. Blueberry seedling of the type with few branches 59 26. Spores of a supposedly injurious fungus in the epidermal cells of blue- berry roots 64 27. Flowers of the blueberry, from 1908 seedlings of the large-berried New Hampshire bush of Vaccinium corymbosum 77 28. Stamens of the blueberry 77 29. Compound pollen grain of the blueberry 78 30. Pistil and calyx of the blueberry, showing the style and stigma 78 31. Blueberry plant grown from a root cutting 86 193 B. r i EXPERIMENTS IN BLUEBERRY CULTURE. INTRODUCTION. Iii the grounds of the Smithsonian [nstitution at Washington are two blueberry bushes of large size and great age. The taller is about 9 feel high. The largesl stem is nearly 3 indies in diameter. It is known that these bushes v\ ere growing prior to L871, thirty-nine years ago, and all the evidence indicates that they were planted at a much earlier date. They are probably over 50 years old." In the Arnold Arboretum, near Boston, are many blueberry bushes 30 years old or more, grown from the ^^l by Mr. Jackson Dawson or trans- planted from their wild habitats prior to L880. The two cases here cited demonstrate the fallacy of the popular idea that the blueberry can not lie transplanted or cultivated. This idea rot- on the unsuccessful experience id' those who have taken up wild bushes and -et them in a rich, well-manured garden soil. These air exactly the condition-, as shown by experiment- described in this publication, under which blueberry plant- become feeble and unpro- ductive. four agricultural experiment stations, those of Maine. Rhode [sland, New York, and Michigan, have attempted to grow the blue- berry a- a fruit, hut none of these attempts ha- resulted in the com- mercial success "f blueberry culture, and the experimental results have boen chiefly of a negative character. This outcome appear- to have been *\\\r to a misunderstanding of the soil requirements of the blueberry, which, as will be shown later, are radically different from those of our common cultivated plan-. " The plants are i actinium atrococcum, n species closely related to Vactinium corymbosum, the well-known swamp or high hush blueberry of the Northern Stales, lu a list of the trees ami shruhs of the Smithsonian grounds prepared by Arthur Schotl in ls~l. these bushes are included, but identified, ho\ ■ i as Vavcinium fuscatum. The hue Mr. George II. Brown, for mere than a gen- eration the superintendent of planting in the parks of Washington, also as- sured the waiter that these plants were not set out since he first became responsible for the Smithsonian grounds, in 1871. The present plan of the grounds was made by Mr. Andrew J. Downing, bul the actual planting was not done until after his death, in 1852. It is possible thai the blueberry hushes may have been set eat as early as 1848, in whicb year a partial planting of the Smithsonian grounds was made by Mr. John I glass. L93 11 12 EXPERIMENTS IN BLUEBERRY CULTURE. In the Boston market there is a wide variation in the wholesale price of blueberries. Shipments begin in early June from North Carolina, followed in the hitter part of the month by blueberries from Pennsylvania, New Jersey, and New York. In early July, or in some years in the last days of June, Massachusetts and New Hamp- shire shipments begin to arrive, succeeded in late July or early August by berries from Maine, Nova Scotia, and New Brunswick. Receipts from these last two localities continue until late September. The blueberries that bring the highest price are those from Massa- chusetts and New Hampshire. At the time when other berries are selling at 8 to 15 cents per quart wholesale, the first shipments of New Hampshire berries often bring 20 to 23 cents. The owner of a blueberry pasture in southern New Hampshire who superintended the picking of his own berries and shipped them to one of the secondary New England cities has courteously shown his shij^ment records, from which the following data have been compiled : Records of shipments from n blueberry pasture in southern New Hampshire, 1905-1909. Year. Date of shipment. Total ship- ments. Highest iuhI lowest price per quart." Average price per quart, a 1905 July 1 to Aug. 14 July 20 to Aug. 15.... June 29 to Aug. 15 July 15 to Aug. 16 Quarts. 2,233 2,756 2,538 3, 602 l , .'. B Cents. 12i to 8 15 to 8 14J to 11 16 to 9± 11 to 9 i 'eats. 10.7 1906 9.6 1907... 12.2 1908 10.8 1909 10.7 a This is the net price that the shipper received after deducting express charges. The average net price for the five years was 10.8 cents per quart. The record indicates the substantial returns that arc secured from ordinary wild berries picked and sent to market in rather better than ordinary condition. That the market would gladly pay a high price for a cultivated blueberry of superior quality there can be no doubt. From the market standpoint the featui'es of superiority in a blueberry are large size; light-blue color, due to the presence of a dense bloom over the dark-purple or almost black skin: "dryness," or freedom from super- ficial moisture, especially the fermenting juice of broken berries; and plumpness, that is. freedom from the withered or wrinkled ap- pearance that the berries begin to acquire several days after picking. While the connoisseur in blueberries who picks his own fruit knows the widely varying flavors in the berries of different bushes, the buyer in the city market is content to select his fruit according to its ap- pearance, knowing that the flavor will be good enough in any event. 193 I 111. PICKING "l l.l.i il-.i RKIES. 13 The size of the seed gives the buyer in Xew England markets verj little concern, for there the name bluebern is restricted to plant- of the genus Vaccinium, all of \\ hich have seeds so small as to be unno- ticeablewhen the berry is eaten, while the name huckleberry is applied with nearly the same precision to the species of the genus Gaylus- sacia, in which the seed is surrounded by a bonj covering like a minute peach pit, which crackles between the teeth. In -out hern cities the fruits of both Vaccinium and Gaylussacia arc called huckleberries, and it is probable that the low estimation in which the fruit of Vac- cinium is there held is largely due to the lack of a distinctive popular name. To distinguish the two berries by their appearance is difficult for any but an expert, for while huckleberries are mostly black and blueberries mostly blue, some of the blueberries, or species of Vac- cinium, are black, and -nine of the huckleberries are blue, notably frondosa, a species often abundant in the sandy soils of the Atlantic Coastal Plain, which has a large, handsome berry of a beautiful light-blue color and passable flavor, but with the disagree- ably crackling seed pit- characteristic of the other true huckleberries. The blueberry withstands the rough treatment incident to ship- ment so much better than most other berries that with proper han- dling it should always reach the market in first-class condition. Bui ii- good shipping qualities are often abused, and the fruit not infrequently is exposed for sale partly crushed and the berries cov- ered with soured juice and made further offensive by the presence of flies. This is the prevailing condition of blueberries and huckle- berries in the market- of Washington, in striking contrast with the dry, plump berries of the Boston market. This had condition i- due usually to improper picking. The small size of the blueberry, compared with other berries, ren- ders the picking of it expensive. The owner- of blueberry pastures commonly pay two-third- the net price of the berries to their pickers. In order to reduce the cost of picking, various devices have b< employed. The mosl widely \\-^^\ of these is an implement known as a blueberry rake, a scoop shaped somewhat like a deep dustpan, provided in front with a series of long, pointed fingers of heavy wire. With this implement an ordinary picker in the blueberry canning districts of Maine, for example, gathers •"> to ■> bushels a day. for which he receives l . to •_' cent- per quart. Blueberries can he picked with a rake at about a fourth the cost of picking by hand. For this reason many of the berries that go to market are picked with a rake, and it i- these berries which, broken and fermenting, make up the greater part of the low-grade stock so offensive to the eye and the ta-te. Blueberries intended for the market should never he picked with a rake. 193 14 EXPERIMENTS IN BLUEBERRY CULTURE. What has been said regarding the high cost of picking ordinary blueberries by hand indicates the importance of securing a berry of large size if the plant is to be cultivated. Large size and abundance mean a great reduction in the cost of picking. Large size mean- also a higher market price, and when taken in connection with good color and good market condition it means a much higher price. The writer's interest was attracted to the subject of blueberry cul- ture in 1906. In the autumn of that year some experiments were made for him by Mr. George W. Oliver to ascertain a suitable method of germinating the seeds. In the autumn of 1907 special cultural ex- periments were taken up. In 1908 experiments were begun in the propagation of bushes bearing berries of large size, the most satis- factory of these being a New Hampshire bush of the swamp blueberry {Vaccinium corymbosum) having berries a little more than half an inch in diameter. The largest berries tried, a little more than five- eighths of an inch in diameter, were from Oregon bushes of Vac- cinium membranaceum. Except where otherwise stated, the experi- ments described in this paper were made with Vaccinium corym- bosum: The principal results of the experiments are given under brief numbered statements, each followed by a detailed explanation. PECULIARITIES OF GROWTH IN THE BLUEBERRY PLANT. soil requirements. (1) The swamp blueberry does not thrive in a rich garden soil of the ordinary type. Although the statement just made might well rest on the direct observation of experimenters who have failed to make blueberries grow luxuriantly, or sometimes even remain alive, in rich garden soils, nevertheless the citation of one of the writer's experiments may serve to accentuate the fact. The soil chosen for the purpose was the one used at the United States Department of Agriculture for grow- ing roses. A sample of this soil, as mixed by the rose gardener, con- sisted, according to his specifications, of " five shovelfuls of loam, one shovelful of cow manure, and a handful of lime." The loam used was a rotted grass turf grown on a rather clayey soil. The cow manure was well rotted, having lain in the pile for several months, with almost no admixture of straw. The lime was of the ordinary air-slaked sort. The pots used in the experiment were of glass, small 5-ounce drink- ing glasses, about 2 inches in diameter at the bottom, 2.1 at the top, and L ;: ; inches dee]). A small hole bored through the bottom gave the necessary drainage t<> the -nil in the pot. Since the walls of these pots were transparent, the normal growth of the roots and the pre- THE USE OF GLASS POl 3. 15 vention of an obscuring green growth of microscopic algse required some arrangement for keeping the light away. This was accom- plished cither by sinking, or, as gardeners say, " plunging," the pots nearly to the rim in sand, moss, or soil, or, when the pots were nol plunged, by fitting closely to the outside of each a removable cuff, as it were, made of the opaque gray blotting paper used in pressing specimens of plant-. The use of a pot with transparent walls was found to l>e of \ ery great importance in the st udy of these plants - , for plant- identical in appearance SO far a- the parts above ground were concerned sometimes showed the most pronounced differences in the growth ami behavior of the rout-, differences which otherwise would not have been observed but which were in reality responsible for the conspicuous changes that later took place in the growth of the -tem< and leave-. The use of such glass pot-, drained and darkened, t- strongly recommended to plant experimenters who use pot cultures, as they afford a mean- of acquiring easily an intimate knowledge of _reat variation- in the behavior of the feeding organs, the roots, under di fferent condit ions. On December •_'•_'. L908, six glass pot- were tilled with the garden -oil described above, and a seedling blueberry about an inch in height was transplanted into each. The -fn\ bed from which, the seedlings were taken had been allowed to become partially dry before the transplanting was done. In this condition there was no difficulty in removing all of the sandy -oil adhering to the roots of a seedlii that after it wa- transplanted it must derive it- -oil nourishment from the new soil exclusively. In potting, the root- of the plant were laid against the jilass on one side of the pot -o that their behavior could he observed from the very first. \ transplanting of six other plant- was then made, similar in all respects to the first except that the soil used was a peat mixture known from earlier experiment- to he productive of rigorous growth in blueberry plant.-. The exact character of this -oil will he discussed later in this publication. Tin- peaty blueberry -oil i- ill suited to the growth of ordinary plant.-, while in the garden soil ordinary plants flourish luxuriantly. I n order to bring out this fact clearly by an experiment six glass pots containing this garden -oil were planted with live alfalfa -ceil- each. and six more with one rooted rose cutting each. An identical planting was made in twelve pots of blueberry soil. A.verage example- of the growth that took place in these plantings arc shown in figures I to 6, reproduced from drawings carefully made from actual photographs. In the garden soil the rooted rose cut- ting, which wa- of the variety known a- Cardinal, made vigorous growth of both root and stem, and in forty-four day-, when the I a:; 16 EXPERIMENTS IN BLUEBERRY CULTURE. photograph was taken, had about quadrupled its leaf surface. In the blueberry soil the cutting was barely alive 1 , the roots it had at the time it was potted were nearly all dead, no new stem growth had been made and the leaflets it bore were only those still persisting from the parent plant. The alfalfa seeds began to germinate in both soils in three days. At the end of a week a distinct difference in the color of the plants was discernible. In the blueberry soil the seed leaves were darker green in color, the midrib, which shows on the back of the leaf, was ! [g. I.- Roso cutting in rich garden soil. 1 1 >ne ba 1 1 na i ura I size, i Fn 2 Rose cutting in peal mix- ture. (One half natural size. purple, the stem was purple, and in some of the seed leaves the whole under surface was purple. In the garden soil the seed leave- were lighter green in color, and in only a few were the stems, and in -till fewer the midribs, some\* hat purplish. At the end of forty-four days, when the photographs reproduced in figures 3 and A were taken, the alfalfa plants in the garden soil were 3 inches in height and vigorous, while lie -oil was crowded with roots on which nitrogen tubercles had already begun to develop. In the blueberry -oil the plant- were small leaved and sickly, about a third the height of the other-, and 193 I N.I I RI01 - EFFEl is OF lilCIl GARDEN SOIL. IT the roots though long were slender and otherwise weak and bore no tubercles. In the case of the blueberry plants the relative growth in the two -nil- took exactly the opposite course. At the end of the first week new root growth had begun in all the pots containing blueberry soil, while in those containing garden -oil new root growth was apparenl in only one. At the end of forty-four days vigorous rool growth had taken place in the blueberry soil pots, and stem growth, which had been interrupted at the time of transplanting, was well under way again. In the garden soil, however, almost no root growth was discernible, il Id leaves were strongly put-pled and stem and leaf growth had nol been resumed. Little attention was paid to these culture- during the summer of L909, but the relative condition of the two is fairly Fig. 3. — Alfalfn seedlings In rich garden soli. Fio. 4. — Alfalfa seedlings In peat mixture. I natural size, i (One-hall natural size, i illustrated in figures 5 and 6, from photographs taken November 22, 1909, after the leaves had fallen. The garden-soil pot contained only .i f< \ stray roots, and the -lender stems were only 2 inches high. The pot containing blueberry soil was filled with a dense mass of roots, and although the plant had not been repotted when it needed repotting, the largest stem was nevertheless 11 inches long and the weight of that part of the plant above ground was fifty-one times that of the corresponding part of the garden-soil plant. (2) THE SWAMP BLUEBERRY Hers NOT THRIVE IN \ 111 w II Y MANURED SOIL. Iii May. 1909, two healthy and vigorous blueberry seedlings were sent for trial to one of the agricultural experi n1 stations. They were set out in a soil that was known to be suitable for these plant-. for old blueberry bushes had been growing there for several years. 54708 Bull. 193 10 2 18 EXPERIMENTS IN BLUEBERRY CULTURE. The man who put the blueberry seedlings in the ground, however, misunderstanding the directions sent him, filled in the holes in which he set the plants with alternate layers of soil and well-rotted stable manure. The writer ex- amined the plants on August "27. 1909, when they should have been either growing vigor- ously or, with mature foliage, ripening their wood for the winter. Instead they had lost nearly all their older leaves (hough still main- taining a feeble and spindling growth at the ends of the larger stems. The adjacent old bushes growing in precisely the same soil, ex- cept that it had not received the heavy appli- cation of manure, bore at the same time vigor- ous dark-green foliage and were ripening the wood of their stout twigs and laying down their flowering buds for the following year. The manured plants when dug up and exam- ined showed no new root growth whatever in the manured soil outside the old earth ball, and most of the roots on the surface of the ball itself were dead. Another experiment may be cited to show the injurious effect of heavy manuring. On December 22, 1908, six blueberry seedlings were transplanted into as many glass pots in a good blueberry soil, ami six other seedlings were potted in the same manner, except that to each 1 wo parts of blue- berry soil one part of well-rotted but un- leached cow manure was added. At first the manured plants appeared, superficially, to he doing better than those not manured, for in the former the pro- duction of new leaves a n d t h e continued growth of the stem tip L93 Pig. 5. Blueberry seedling in rich panlcn soil, i < >nc hiilf natural size, i Fig. 6. Blueberry seedling in peat mixture. (One- half natural slz6.) BLUEBERRIES WANTING ! N LIMESTONE SOILS. 19 were not interrupted by the potting, while in the plants nol manured there was a temporary 1 > 1 1 1 definite stopping of stem growth imme- diately after the potting. The apparent superiority of growth in the manured plants, above ground, continued for about three weeks. Be- liiw ground, the roots of the two cultures showed directly opposite results. In the plants without manure, new root growth began a few days after potting. At the end of three week- the development of an extensive tern was well under way and the plants were nearly ready for a period of \ igorous stem growth. In the manured plants. however, either do root growth took place or only a slight amount. the new rootlets being fewer, shorter, and stouter than in normal plant-. The old rootlets tinned brown and appeared to be dead or dying. (See p. 64.) At the end of live week- the growth of the tops was N'-ry slow. About ten day- later, on February 6, a bright warm day, the lower leaves on three plants withered, and within a few week- all six of the manured plants were dead. I .". I Till SWAMP BLUEBEBIH S KOI THRIVE IN \. SOIL MADE SWEET B1 LIME. Iii its natural distribution the blueberry, like almosl all plants of this and the heather family, avoids limestone soils. The fertile limestone areas of western New York, of Ohio, of Kentucky, and of Tennessee lack the blueberry, the huckleberry, the laurel {Kalmia Jatifolia), and the trailing arbutus (Epigaea repens). The State of Alabama, as described by Charles Mohr in volume 6 of Contri- butions from the United States National Herbarium, is traversed from east to west in the general latitude of Montgomery by a strip of dark calcareous soil, 35 to r> miles in width, the so-called "black belt," which constitutes the great agricultural region of the State. The noncalcareous area- north and south of this strip have in their i- a characteristic undergrowth of blueberries and closelj re- lated plant-, including huckleberries, farkleberries, and deerberries. In the intermediate belt of Mack limestone soil, just described, the plant- of blueberry relationship are almost wholly wanting. In an article entitled "The Soil Preference- of Certain Alpine and Subalpine Plants," Mr. M. L. Fernald discusses the natural distribution of over 250 species of plants found in the cold parts of the northeastern United Mate- and Canada. All the blueberries umerates, five species, avoided calcareous -oil-, ami the other plants of the blueberry and heather families almost without excep- tion occurred likewise on noncalcareous formation-. The writer'- own experiments in growing blueberries in limed -ml- have not proceeded with the same -inoothne- of his other experiments, but the results, though at first misleading, have uniformly been exceedingly instructive, though not always in the Rhodora, vol. 0, mo?, pp. L49 L93. 193 20 EXPERIMENTS IN BLUEBERRY CULTURE. direction originally contemplated, and in the end have been fully conclusive. On May l ; <'>. 1008, six blueberry seedlings were potted in six 14- ounce drinking glasses in a good peaty blueberry soil, in which, however, 1 per cent of air-slaked lime " had been mixed immediately before the potting was done. Six other plants were similarly potted, but without the addition of lime. The unlimed plants grew normally. The younger leaves of the limed plants, however, began to wilt the same day on which they were potted. On June 1 all the leaves on all six plants were withered, though parts of the steins were still green and plump. The leaves did not turn purplish or yellowish, as is usual with sickly blueberry plants, but either re- tained their green color after withering or turned brown. No new root growth took place in any of the limed pots, and by July 10 all the plants were dead. Another series of six plants, also potted on May 26, 11)08. but m a sterile soil containing no peat, by accident received a very small amount of lime. Most of the leaves on these plants withered during the first few days, but the plants subsequently recovered and made as good growth as could have been expected from the general char- acter of their soil. From these experiments the writer concluded that the blueberry was exceedingly sensitive to lime and that the slightest admixture of it in the soil would be immediately fatal to the life or at least the health of a blueberry plant. This conclusion, however, was erroneous, as subsequent experience showed. This first experiment may therefore be dismissed with the explanation that in all proba- bility the immediate collapse of the plants was due to a caustic effect of the lime used. In none of the later iime experiments did this immediate collapse occur and in none was the lime so applied that it came into contact with the blueberry roots while in a caustic condition. Still laboring under an erroneous conception of the supersensi- tiveness of the blueberry plant to minute quantities of lime, the writer, desiring to produce fresh examples of this phenomenon, in November, 1008, placed a very small quantity, a few milligrams, of air-slaked lime on the surface of the soil in each of three '-'-inch pots containing a small blueberry plant. No effect was produced either at first or for several weeks. On December 19, L908, a large surface application of carbonate of lime was made to the same three plants, a gram to each pot. and the lime was washed down with water. The expected collapse did not occur. The limed plants con- tinued to grow as luxuriantly as their unlimed neighbors. The coh- Computed en (lie dry weight of the soil. i !>:: >l,<>\\ PERI OLATION M I. CHROUGH PEAT. 21 elusion \\ as reached that the reason why the growth of the plants had not been affected was because the lime had nol penetrated sufficiently ititD the soil. Another and more drastic experiment was therefore determined upon. On March LO, L909, sis blueberry plants in Pinch pots containing :: good blueberry soil were sel apart from their fellows and watered with ordinary limewater, a saturated solution of calcium oxid, 1.25 grams per liter of water. The applications made were of such an amount that the soil in the pot was thoroughly wetted cadi time, and usually a small excess quantity ran through the hole in the bottom of the pot. For more than seven months, until October 22, 1909, these pots received no other water than limewater. During this period the plants continued to grow in a normal manner, their average height increasing from I' to II inches. The lime appeared to have no deterrenl effeel whatever on the growth of the plant-. A computation based on the total amount of limewater used showed that each pot must have received about 18 grams of lime. An analysis of the -nil in one of the puts after the limewater applications had ceased gave II grams. This amount was enormous, considered from the stand- point of agricultural usage. The soil, which had about one-third the weight of an ordinary soil, was over 8 per cent lime. This is the equivalent of aboul 25 ton- of lime per acre mixed into the upper »'. inches of the -oil. Now.it was already known from the experiment described on page '_'•"> that in this soil when containing as much as 1 per cent of lime blueberry plants should either die or barely remain alive. A- a matter of fact these limewater plant- were making excellent growth. A careful examinati f the contents of one of the pot- vva- then made. The surface of the -oil was covered with a hard gray crust of lime. Immediately underneath for a depth of about half an inch the oil was black and contained no live blueberry root-. There was a zone of the same black rootless -oil along the wooden label that reached from the top to the bottom of the pot. In all other parts of the dark-brown peaty -oil there was a dense mas- of healthy roots, which reached down also into the open -pace- among the broken rocks in the bottom of the pot. The lime appeared to have penetrated only into the superficial portions of the -oil. A chei howed that the Mack rootle-- layer was densely impregnated with lime, while the brown peatj portion containing the growing root- -till gave the acid reaction thai vvas characteristic of the whole potful of soil he I ore t he limewater applications began. Since all the water that the limeless root-bearing portion of the soil had received during the preceding seven month- had come from the limewater applications, it was evident that the lime contained 193 22 EXPERIMENTS IN BLUEBERRY CULTURE. in the limewater had been deposited in the upper layer- of the soil. The following laboratory experiment confirmed this. A small quan- tity of the acid peaty soil used in growing blueberries was placed in a glass vessel and moistened. Then dilute limewater reddened by the addition of phenolphthalein. a substance giving a delicate color test for alkalies such as lime, was stirred into the soil and the mixture poured into an ordinary paper filter. The water came through the filter without a trace of red color, showed none after boiling, to drive off any possible carbonic acid, and when tested with ammonia and ammonium oxalate showed not a trace of lime. The precipitation of the lime had been complete and practically instantaneous. Only ten seconds had elapsed between the time when the limewater was added to the soil and the time when the liquid entirely free from lime began to drop through the filter. In order to ascertain whether a large part of the lime in the lime- water used on the plants may not have passed through the pots by running down the partially open channel along the label, some lime- water was poured upon the surface of one of the pots. The excess water that soon began to drip through the bottom of the pot was tested for lime. It was found that while the limewater poured into the pot contained 0.1014 per cent of lime, the water that came through contained only 0.0046 per cent. In other words a pot of soil that for over seven months had been used essentially as a limewater filter still continued to extract over 95 per cent of the lime contained in the limewater that was passed through it. notwithstanding the fact that there was a partially open channel down one side of the pot. It is believed that had the soil been evenly compacted in the pot no lime whatever would have been able to pass through, hut that all would have been precipitated in the uppermosl layers. While the experiment ha- no important bearing on the subject of blueberry culture it is of very great significance in its bearing on the method of applying lime to acid soils in ordinary agricultural prac- tice. A surface application id' lime would have no appreciable effed in neutralizing the acidity of a soil unless the -oil was so sandy or gravelly or otherwise open that the rain water containing the dis- solved lime could run down through it practically without obstruc- tion. A surface dressing of lime would have little effecl in neutraliz- ing the acidity of an old meadow or pasture. To secure full action of the lime, as now generally recognized in the best agricultural practice, requires its intimate mixing villi the -oil. such as can be accomplished by thorough harrowing, especially after putting the lime beneath the surface with a drill. A full discussion id' the phys- ical reasons for the deposition of the lime in the upper layer- of the -oil. when not worked into it mechanically. i< given in Bulletin .V_' of Bureau of Soils, published in 1 DOS. [NJUBI01 S II II I I OF LIME Among the experiments with blueberry seedlings in different soil mixtures started on December 22, L908, was one in which six plants set in »lass pots in ;i peaty soil thoroughly intermixed with 1 per eenl of carbonate of lime. The first difference that showed be- tween these and unlimed plants in the same soil was the much feebler root growth of the limed plants. This was followed by an evident tendency toward feebler stem growth. The relative condition of the two cultures on April 13, 1909, is shown by photographs of represent at iw plants reproduced as figures 7 and 8. The later progress of this Bluebern s Illns in peal mixture Fig. 8. Blm tiling In peal mixture limed. (One-naif natural size.) unlimed. (On< uralsize.) experiment was interrupted, however, and its average results vitiated -c the roots of -nine of the limed plants found their way through the holes in the bottom of the pot- and obtained nourishment from the unlimed material in which the pots were plunged. Such plants made nearly as good growth as the unlimed plants. On November 27, 1909, there remained only one of the limed plants whose root? were all inside the pot. This plant was feeble and small, its stem being only •_'! inches high, lis inferiority to the unlimed plant- was almost as conspicuous as that of the garden-soil plant- described on 17 and illustrated in figure 5. 24 EXPERIMENTS IN BLUEBERRY CULTURE. (4) The swamp blueberry does not thrive in a heavy clay soil. In its natural geographic distribution the blueberry shows an aversion to clay soils. Its favorite situations are swamps, sandy lands, or porous, often gravelly loams. When a blueberry plant grows upon a clay soil it is usually found that its finer feeding roots rest in a layer of half-rotted vegetable matter overlying the clay. Often in such situations the dense covering of interwoven rootlets and dark peatlike soil may be ripped from the surface in a layer little thicker than a door mat and of much the same texture. The roots of the blueberry do not penetrate freely into the underlying clay. In greenhouse cultures the blueberry shows the same aversion to clay soils. Various series of blueberry seedlings were potted on May 26, L908, in different soils in ordinary large drinking glasses. For one set of six plants a stiff clayey soil was used, such as is common in the neighborhood of Washington, D. C. The soil in the glass was mulched to the depth of nearly an inch with half-rotted leaves. In another six glasses were set six similar plants in a peat soil, the sur- face mulched in the same way as the others. In other experiments with this clay soil in earthen pots, the growth of the plants had always been poor. The present experiment was no exception. But the feature of greatest interest was the behavior of the roots. Plate I, from photographs taken October 5, 1908. shows the root systems of typical plants in the two soils. In the clay soil almost no root development took place, and in the illustration no routs are visible. The interrupted black lines in the clay are tunnels made by larva; or other animals. In the moist leaf mulch covering the clay, however, the plant developed its roots extensively. Some of the plants, probably because they were set too deeply in the clay when the potting was done, failed to send their roots up into the mulch, and such plants were much inferior in their growth to those that found the rotted leaves. In the other gins- i- shown the normal root growth of a blueberry in a soil suited to it. (5) The swamp blueberry does not thrive in a thoroughly decomposi d leaf mold, such as has a neutral reaction. It had been found in earlier experiments that certain -oil- com- posed in part of imperfectly rotted oak leaves were good for growing blueberries. On the supposition that the more thoroughly rotted this material was the better suited it would be for blueberry growing, a quantity of old leaf mold was secured for an experiment. The mold was black-, mellow, and of fine texture. The mixed oak and maple leaves from which it was derived had been rotting for about five years, until all evidences of leaf structure 1 had disappeared. It had the same appearance a- the black vegetable mold thai form- in rich woods where trilliums. spring beauty, and bloodroot delight to grow. 193 Bui. 193, Bureau of Plant Indjstty. U. S. Dep: Plate I. £ ■ 1 1 i m IN. i [JRIOUS Mil.' I OF l.l \l MOLD. 25 On February 20, L909, 25 blueberry seedlings were potted in ".-inch earthenware pots in a mixture consisting of eight part- by bulk oi the leaf mold just described, one part of clean sand, and one pari of clayej loam derived from rotted grass turf. Fifty other plant- were potted in the same manner except that in place of the mold a peat was used known from earlier experiments to be well suited to blui berrj growing. The plant- were kept in the greenhouse until warm weather when they were placed outdoor-. All were given the same treatment, a treatmenl favorable to good growth. It had been expected that the plant- in the leaf mold would -how a vigorous growth, and it was hoped that the mold might prove even superior to the peat for blueberry soil mixture-. The experiment as ii progressed, however, showed that such was not the case. The leal* mold proved to be not merely not a good soil for blueberries but an extremely pom- one, as the following particular- will -how. When the plants were potted they averaged about •_'! inches in height. On May 29 the peat-soil plant- had an average heighl of ~\ inches, while the leaf-mold plant- averaged 1] inches. At this time the herbage of the leaf-mold plant- was decidedly purpled and yel- lowish, a coloration which they had taken on SOOn after they were polled and from which they never fully recovered. At the end of the season, after the leaves were shed, the peat-soil plants averaged \'-\\ inches in height and the lea f-mold plant- 7 | inches. < )n November 29, 1909, five average plant- from each lot were cut oil' at the surface of the ground and weighed. The weight of the stems from the lea f-mold plant- was less than one-fifth that from the plants in the good blue- berry -oil. When these plant- were removed from their original seed bed to he transplanted to the 3-inch pots, such of the original -oil as clung i" their i""' was not shaken off. It ; - believed that the leaf-mold plant- U->\ in part on this original -oil in making their new growth, and that without it they would have shown -till less increase in height than tiny did. The peat-soil plant-, moreover, were badly in need of repotting, even in early summer, and had they been placed in larger pots the difference in the growth of the plant- in the two soils would have been much greater than it was. That the influence of the leaf mold wa- directly deleterious and thai the i r growth of the blueberry plants in it wa- not due t < . the lack of some element that might have Keen furnished by the addition ■ I a -mall amount of the good blueberry -oil i- shown by certain inter mediate experiment-. A.long with the culture- described above were carried two other- in which the -oil mixture- contained both peat and leaf mold. In the first, in which the proportion wa- peat '>. mold 3. -and 1. and loam 1. the average height of the plants on May 29 26 EXPERIMENTS IN BLUEBERRY CULTURE. was 6 inches, and at the end of the season 124 inches. In the second lot, in which the proportion was peat 3, mold 5, -and 1. and loam 1, the average height on May 29 was 44 inches, and at the end of the season llf inches. It will be observed that these two lots of plants are intermediate in their growth between the first two and that in all four lots the poverty of growth is roughly proportional to the amount of leaf mold used in the soil. That the weak growth of the plants in leaf mold was not caused by a compacting of the soil and a lack of aeration, due to too small a proportion of sand in the mixture, is shown by still another lot of 25 plants which were potted in a soil mixture having the proportion of mold 6, sand 3. and loam 1. These plants averaged only 4 inches in height on May 29 and 6^ inches at the end of the season. They grew even less, therefore, than the plants with only 1 part of sand and 8 parts of mold. In Plate II, from a photograph made in the winter of 1909-10, is shown a flat divided into three parts and set on February 10, 1909, with blueberry seedlings of uniform size. The soil in the middle compartment is a mixture of leaf mold 8 parts, sand 1 part, and loam 1 part. Iii the compartment to the left the soil is in the proportion of kalmia peat 8. sand 1. and loam 1; and in the right diand com- partment, kalniia peat 4, leaf mold 4, sand 1, and loam 1. It will be observed that the greater the amount of leaf mold the poorer the growth of the blueberry plants. The reason for the unexpected deleterious effect of leaf mold, as shown by these experiments, is given on page 29 and further discussed on page 35. (6) The swamp blueberry does not thrive in soils haying a neutral on ALKALINE REACTION, BUT FOR VIGOROUS GROWTH IT REQUIRES AN ACID SOIL. The consideration of this statement requires first an understanding of the means used to determine whether a soil is acid or alkaline. The simplest means is the litmus test. While one may become sufficiently expert in the use of the litmus test to form a fair judgment of the degree of alkalinity or acidity in a soil, an exact determination requires some different method, li was found that for the weak acids prevalent in the peat soils to the examination of which the present experiments led. the phenol- phthalein test was the most satisfactory. II' a few drop-- oi phe- nolphthalein indicator be added to a solution, the solution, if alkaline, turns instantly pink, and if acid or neutral its color does not change. The application of this phenomenon to the determina- tion of the degree of acidity of an acid solution i- as follows: A definite amount of the solution, usually 100 cubic centimeters, is placed in a beaker, a few drops of an alcoholic solution of phenol- 193 Bui. 193, Bu' ry, U. S. Dept. of Agriculture. Plate II HOD OF Ti - OIL v inn i . 27 phthalein are added, and into this is stirred drop by drop from m graduated glass tube provided with a stopcock, known as a burette, a measured amount of some alkaline solution of known strength, commonly a one twentieth normal solution, as ii is known to chem- ists, of sodium hydrate. When a sufficient amount of the sodium- hydrate solution has been dropped into the beaker, the acidity of the acid solution becomes neutralized and ii turns pink. A reading is made on the burette showing the exact amounl of the sodium-hydrate solution used in effecting the neutralization. From this reading is computed the degree of acidity expressed in fractions of a normal acid solution. Now LOO c. c. of a normal acid solution would require for it- neutralizat ion LOO c. c. of a normal solution of sodium hydrate, or 2,000 c. c. of a one-twentieth or 0.05 normal solution. In a test of one of the acid nutrient solutions used in the blueberry cultures, L8 c. c. of :i 0.05 normal solution was required to neutralize the acidity of LOO c. c. of the acid solution. Since L8 c. c. of a 0.05 normal .solution is the equivalent of one-twentieth that amount, or 0.9 c. c. of a normal solution, the degree of acidity of this acid solution is 0.009 normal. It requires an equal amount of a 0.009 normal alkaline solution to neutralize it. In applying this phenolphthalein test to soils the same scale is used. A soil i- regarded as having normal acidity when the acid ex- isting in a gram of the soil if dissolved in 1 c. c. of water gives a nor- mal acid solution. If a soil were described as having an aciditj of 0.02 normal, it would mean that the extract of LOO grams of it in 100 c. c. of water would be a 0.02 normal acid solution; that is. that LOO C c. of the solution would contain -1 c. c. of a normal acid solution. 'The method of extraction followed for all the soil acidity tests given in this paper is a- follow-: The -oil is first air dried at an ordi- nary room temperature. Ten grams are then weighed out. shaken thor- oughly with 2 <■. of hot water, and allowed to stand oxer night. In the morning too c. c. is filtered oil' and boiled to drive away any carbon dioxid present. The solution i- then titrated with a 0.05 mill solution of sodium hydrate, using phenolphthalein a- an indi- cator. All the tests were made by Mr. .1. I-'. Breazeale. of the Bureau of Chemistry, to whom the writer i- greatly indebted for many cour- tesies and suggestions on the chemical side of the experiment-. The expression •■normal solution " used in this paper, it must be understood, i- the normal solution of chemists, not of surg Surgeons use the expression " normal -alt solution '" to describe a cer- tain weak solution'of common salt in water which has the same osmotic pre— ure a- the blood. A normal solution in chemistry is a solution of certain fixed strength, or concentration, based on the molecular weight of the substance under considerat ion. Normal solu- 193 28 EXPERIMENTS IN BLUEBERRY CULTURE. tions of the various acids have the same degree of acidity. Normal solutions of alkaline substances are equal to each other in alkalinity. A measured amount of a normal solution of an acid will exactly neutralize an equal amount of a normal solution of an alkaline sub- stance. In considering the degree of acidity from the standpoint of the sense of taste it is convenient to remember that the juice of an ordi- nary lemon is very nearly a normal solution of citric acid. The juice of the lemon contains usually from 6 to 7 per cent of citric acid. A normal solution of citric acid is 6.4 per cent. When the juice of a lemon is diluted to about ten times its original bulk, as in a large drinking glass, one has approximately a 0.1 normal acid solution. When diluted to 100 times, making about a 0.01 normal solution, there remains only a faint taste of acidity. The acidity of water after standing long in contact with peat in a barrel sometimes reached 0.005 normal. Bog water, or peat water, is sometimes appreciably acid to the taste. Returning now to a consideration of the statement that the swamp blueberry does not thrive in a neutral or alkaline soil an experiment in this direction may first be cited, The experiment was made with twelve small glass pots, each containing a blueberry seedling. The soil in the pots was a clean river sand. The plants had been in these pots for eight weeks, watered with tap water. The amount of nourishment they had received during this time was therefore very small, especially since, when transplanted into the pots, all the soil of the original seed bed had been carefully removed from the roots. Nevertheless during these eight weeks all the plants had made exten- sive, even luxuriant, root growth. The tops, however, had made no growth. There had been complete stagnation or withering of the youngest leaf rudiments, and the mature leaves became and remained deeply purpled. Beginning on February IT, 1909, eight weeks after the plants had been potted in the sand, as already stated, Ww of the pots were wa- tered with an acid nutrient solution made up. in accordance with the advice of Mi-. Karl F. Kellerman, of the Bureau of Plant Industry, as follows: Potassium nitrate (KX<> :: ) 1. Ogram. Magnesium sulphate (MgS0 4 ) 0.4 gram. Calcium sulphate M';iS<>,t 0.5 gram. Calcium monophosphate (CaHiPsO | 0.5 gram. Sodium chlorid (NaCl) 0.5gram. Ferric chlorid (FeCU) Trace. Water 1, 000 c. c. This solution gave an acidity test of 0.012 normal. 193 [NJURIOUS MM' 1 OF ALKALINE SOILS. 29 Five other plants from the same twelve were watered with an alka line nutritive solution of the following composition : Potassium nitrate (KNOa) 1.0 gram. Magnesium sulphate (MgSO i 0, Lgram. Calcium sulphate (CaSO<) O.Sgram. Potassium diphosphate (KH»PO*) 0.4gram. Sodium chlorid (NaCl) 0.5 gram. Ferric chlorid i FeCla) Trace. Water l.OOOc.e. By the addition of a sufficient quantity of sodium hydrate the re- action of tlii- solution was made alkaline to the degr< f 0.006 normal. Two of the twelve plants were left as checks, being still watered w ith tap water. On March l'.~>. thirty-six days after the watering began, the five plants fed with the acid nutritive solution were restored to a nearlj normal green color, and all had begun to put out healthy new growth. The two check plants watered with tap water were -till red-purple and stagnant. Of the five plants watered with the alkaline nutrient solution, three were stagnant and somewhal purplish, one was dying, and one w a- dead. Figures 9 and 10, from photographs taken on April L5, 1909, -how ;i typical stagnant plant that had been watered with the alka- line solution, ami a typical plant watered with the acid solution which had begun to make new growth from the summit of the old -tern and was pushing out a vigorous new shoot from the base. The experi- ment was terminated not long afterwards, but there was every pros- pect that had it been continued the acid fed plant- would soon have made grov th comparable with that shown in figure 8 (p. 23). Looking toward the acidity or alkalinity of the other culture- thus far cited, it maj be stated that the rich garden soil described on pag 1 I. which was so remarkably deleterious to blueberry seedlings, was alkaline. The r — cuttings and the alfalfa, which grew so well in that mixture, much prefer a somewhat alkaline soil. Indeed, alfalfa can not be grown with any degree of success in any soil except one with an alkaline reaction. When grown in the humid eastern United States alfal fa is rarely successful, except on calcareous soil-, unless the natural acidity of the soil has Keen neutralized by suitable applical ions of lime. I ■ limed soil, deleterious to blueberry plant-, described on page 23, gave a neutral reaction with phenolphthalein. The heavy clay soil described on pap' 24, in which blueberry plants made very little growth, was neutral. The thoroughly decomposed leaf mold described on pages •_'! to 26, winch was shown by experiment to be markedly deleterious to the 103 30 EXPERIMENTS IX IJLU 1.111. UKY ( I'L I UP.E. blueberry, was distinctly alkaline A chemical analysis of this mold showed thai it contained 2.86 per cent of calcium oxid. The good blueberry soils in all the experiments were acid, the acidity at times of active growth varying from 0.025 norma! down to O.OO.j normal. It is of interest and suggestive of utility in indicating the acid or nonacid character of soils to record that in the case of the alkaline leaf mold described on page 24 the surface of the soil in all the pots became covered in a few months with a growth of a small moss iden- tified through the courtesy of Mrs. N. L. Britton as Physcomitrium /in an rsum. On the sur- face of acid kalmia-peat -nil- the characteristic green growth consisted of microscopic alga 1 , accom- panied often by fern pro- thallia and other mosses, but never Physcomi- trium. The natural distribu- tion of blueberries and their relatives indicates their close adherence to acid soils. They occur in abundance throughout the sandy ( !oastal Plain of the Atlantic seaboard. They occui' generally through the cool humid hill lands of New England. They occur in sandy pine bar- rens a ad ]> e a t bogs throughout the eastern United States. They are absent, on the contrary, from limestone soils, rich bottom lands, and rich woods, where the soils are neutral or alkaline. In the lower elevations of the whole subarid West, where acid soils are almost unknown, these plants do not occur. Within reach of the fogs and heavy rainfall of the Pacific coast or on the higher mountains of the interior, where conditions favor the devel- opment of acid soils, blueberries occur again in characteristic abun- dance. From an examination of the report- of those who have attempted ai the agricultural experiment stations to domesticate ami improve i lie blueberry, it is evident in the light of the present experiments that the primary reason for these failure- was that they did not recog- L93 Fig. :>. Blueberry s lling fed with alkaline autrienl solution, i Natural size. ) i;l N EFICIAL EFFEI I OF PEAT. nize soil acidity as a fundamental requirement of these plant?. Ii was perhaps natural to give the blueberry the -nine garden cultun thai when applied to other bush fruits has resulted in their distincl improvement. Bui the ordinary garden operations tend to make even an acid soil neutral or alkaline, and in such a soil the blueberry does not thrive. The death and decay of blueberry roots, with which the injurious effect of alkaline soils is associated, are discussed on pages 64 an (7) Tin FAVORITE TYPE OF ACID SOU FOB rH SWAMP BLUEBEKm IS PEAT. Although the swamp blueberry sometimes grows on upland -oil- it- typical habitat, as its name implies, is in swamps or bogs. The cranberry, it is well known, is cultivated al- most exclusively in bogs. In clearing bog land pre- paratory to the planting of cranberries one of 1 he necessary precautions is to remove all roots of the swamp blueberry. I f the roots are allowed to re- main in the ground, they send up vigorous shoots, and these, unless pulled, de\ elop into robust plants v\ hich occupy the ground to the great injury of the cranberries. Large, healthy, and productive bushes of the swamp blue- berry are frequent, almost characterisl ic, inhabitants of the uncultivated bor- ders of cranberry bogs. Peat bogs, in the con- ception of geologists, are incipient coal beds. The transformation of peat into coal occupies verj long perioi Is, perhaps some millions of years. Teat is made up chiefly of vegetable matter. the dead leaves, stems, and root-, of bog plants which are only partly decayed. Their full decay IS prevented primarily by the presence of water, which keep- away the air. The bacteria. Fig. II B I with :\c-iil mil li.iii solul Ion. i Sal ural size, i 32 EXPERIMENTS IN BLUEBERRY CULTURE. fungi, and other organisms by which ordinary decomposition pro- gresses can not live under this condition and decay is suspended. The acids developed by this vegetable matter in the early stage- of its decomposition are also destructive to some of the organisms of decay, especially bacteria. These acids act therefore as preserva- tives and greatly assist in preventing decomposition. So effective are these conditions of acidity and lack of oxygen, assisted in north- ern latitudes by low temperature, which is also inimical to the organ- isms of decay, that bogs sometimes preserve for thousands of years the most delicate structures of ferns and mosses. Tests have been made of the acidity of typical peat bogs in New England where swamp blueberries are growing. These peats were always found to lie acid and the degree of acidity was within the range found satisfactory for blueberry plants in pot cultures. The reason why peat is a particularly satisfactory t) T pe of acid soil for blueberries is, apparently, because the acidity of peat is of a mild type, yet continually maintained. Xot all peats are acid. About the larger alkaline (but not destruc- tively alkaline) springs of our southwestern desert region are deep deposits of rather well-decayed vegetable matter that must be classed as peat. The characteristic vegetation growing on these peats is tide (Scirpus occidentalis and S. olneyi). The water of one of the great tide swamps of the West (Lower Klamath Lake in southern Oregon), which contains thick beds of peat formed chief!) from Scirpits occidentalis, has been examined recently by Mr. J. F. Breazeale, at the request of Air. C. S. Scofield. It was found to con- tain sodium carbonate, and the peat gave a distinctly alkaline reaction. The peat formed about marl ponds in the eastern United State- is also, in all probability, alkaline unless formed at a sufficient dis- tance from the lime-laden water to be beyond the reach of its acid- neutralizing influence. Such alkaline peats, while not actually tried, are believed from other experiments to be quite useless for growing blueberries. Cer- tain it is that neither blueberries nor any of their immediate relatives are found on these soils in a wild state. In the eastern United State-, however, such alkaline peats are comparatively rare, and the use of the word " peat " conveys ordinarily the idea of acidity. All the soils used by gardeners under the name of peat are acid. (S) I'lVI SUITABLl FORTH] SWAMP BLUEBERRY MAT B] FOUND EITHER IN BOGS OR ON Till SURFACE OF Till GROl Mi l \ SANDY OAK OR PINE WOODS. In the vicinity of Washington deposits of bog peat are few and of limited extent, and the peat is thin. As a matter of fact no bog peat of local origin is used by the gardeners and florists of Washington. For growing orchids, ferns, azaleas, and other peat-loving plants. either peat shipped from New Jersey is used or a local product some- 193 I i IRM \ I [ON OF KAI..MIA PEA I . 33 times known as " Maryland peat." This material is not a bog peal a< all, and since it isof very great interest in connection with these blue- berry experiments, for it was the principal ingredient in a majority of ilic successful soil mixtures used, it is desirable that the reader have m comprehensive idea of its character. Maryland peat, as brought to the greenhouses of the United States Department of Agriculture, consists of dark-brown tin- I's <>r mats, 2 to I inches thick, made up of partially decomposed leaves interlaced with fine roots. It is found in thicket- of the American laurel {Kalmia latifolia) where the leaves of this shrub, usually mixed with those of various species of oak, have lodged year after year and the ac- cumulated layer- have become partly decayed. The nature of the deposit may be easily comprehended by means of the accompanying illustrations. The photographs from which the illustration- were made were secured through the courtesy and skill of Mr. (i. X. Collins, of the Bureau of Plant [ndustry. The photo- graphs were made in the month of April. 1908, in a laurel thicket at Lanham, Md. Alter one photograph was made, the layer of leaves represented by it was removed and another photograph was taken showing the layer immediately underneath. hi I Mate III. figure 1. is shown the top layer of the lea I' deposit as it appeared in April, L908, consisting of oak leaves of various species which fell to the ground in the autumn of 1907. The next under- lying layer is shown in Plate III. figure 2. The laurel leave- here shown are those that fell in the summer of L907. Laurel being an evergreen, it- leaves arc not shed in the autumn like those of the oaks. They remain <>n the hush until the new leaves of the following spring are fully developed and then the old leave- begin t<> fall. It is this circumstance of the fall of the oak and laurel leaves at different periods of the year that enables one to recognize the differenl layers and know their exact age. The third layer, shown in Plate 1 V. figure 1. consists of oak leave- of the autumn of 1906. This layer was moist and decomposition was well started. The presence of fungous growth i- evident, a- i- also the excrement of various -mall animal-. Myria- pods, or thousand-legged worm-, and the larva' of insects must play a very important part under some conditions in hastening the de- composition of leaves. The fourth layer. Plate [V, figure 2, consist- ing of laurel leaves shed in the summer of L906, is in aboul the same condition a- the preceding layer. In the fifth layer. Plate Y. figure 1, are shown the leaves of L905, hut the layer of oak leaves is not readily separable from the laurel. The rotted leaves crumble readily and decomposition has so far progressed that a few oak rootlet- arc found spread out between the Rattened leave-. Plate Y. figure •_'. -how- the rotted lea f layer- of 1904 interlaced with the rootlets of laurel and oak. It i- this root bearing layer. 2 inches or more in thickness, of which 54708°- Bull. L93 L0 3 34 EXPERIMENTS IX BLUEBERRY CULTURE. Maryland peat is composed. The lower portions of it reach a some- what greater degree of decomposition than is here shown. In a rich woods of the trillium-producing type, such as a fertile sugar-maple forest, one may observe that the leaves in rotting sel- dom retain their form longer than two years and that the line of de- marcation between the thin leaf litter of the forest and the underlying woods mold is sharp and clear. In the sugar-maple woods the decomposition of the leaves i- rapid. In the Maryland or kalmia peat, as it may he called with more exact- in--, the decomposition i- slow. The cause of this difference in the rate of decomposition is the difference of acidity in the two cases, and this in turn is dependent on the nature of the leaves and of the under- lying soil, particularly whether the soil is acid or alkaline. A slight alkalinity in a soil greatly favors the decomposition of the leaves overlying it. An acidity as strong as that shown to occur in newly fallen oak leaves (see p. 62) can not help having a pronounced effect in maintaining the acidity of the lower leaf layers; for it must he rememhered that these acids are soluble in rain water, ami are there- fore continually leaching down from the upper through the lower layers of rotting leaves. These upland leaf deposits, in which decomposition is retarded for many years, the writer regards as essentially peat, and lo distinguish them from hog peats he would call them upland peats. An upland peat may lie described as a nonpaludose deposit of organic matter, chiefly leaves, in a condition of suspended and imperfect decompo- sition and still showing its original leaf structure, the suspension of decomposition being due to the development and maintenance of an acid condition which i> inimical to the growth of the micro-organisms of decay. The use of the name " leaf mold," sometimes applied to this upland peal. -I Ill lie restricted to the advanced stages in the decomposition of leaves, in which leaf structure has disappeared. True leaf mold, furthermore, is neutral or alkaline, so far as tested. When kalmia peat is to he used for growing blueberries it should he piled and rotted for several months. An experience which empha- sizes the need of this treatment is given on page 60. If slacked as soon as if is dug it usually retains sufficient moisture to carry the rotting forward, even if the stack is under cover. Kalmia peat has proved to he a highly successful soil for growing blueberries. It has been tried both pure and in many mixture-, as will he described in (he paragraphs beginning on page 51. An upland peat formed of the leaves of scrub pine (Pinus virgin- iana) has also been tried for blueberry seedlings. They grow well in it. Oak leaves, it is believed, rotted for one or two year- would make a good blueberry -oil. In the Arlington National Cemetery is a ravine 103 Bui. 193, Bu , U S. Dept. of Agriculture Plate III. Fig. 1.— Formation of Kalmia Peat, Top Layer. Oak leaves of the preceding autumn. (Natural size.) Fig. 2.— Formation of Kalmia Peat, Second Layer. Kalmia leaves of the preceding sumn i Natural size.) Bui. 193. Bureau of Plant Industry. U. S. Dcpt. of Agriculture. Plate IV. Fig. 1.— Formation of Kalmia Peat, Third Layer. (ink leaves 2 years old. (Natural size.) Fig. 2.— Formation of Kalmia Peat, Fourth Layer. Kalmia leaves 2 years old, (Natural si Bui. 193, Buruau of Pa-! Ii dustiy U. S Dept. of Agriculture. Plate V. Fig. 1.— Formation of Kalmia Peat. Fifth Layer. Mixed oak and kalmia leaves 3 years old. A few \i\ of oak are shown, i Natural si/A'. | I i. 2. -Formation of Kalmia Peat, Sixth Layer. Mixed oak and kalmia leaves I yearsor more old interlaced with live rootlets of oak and kalmia. \ . r J • I I \ OF BOGS vND SANDY UPLANDS. 35 in which large quantities of leaves, chiefly oak, have been dumped for iM.Mi\ years. Samples taken there in laic November, L909, -how an acidity in the case of freshly fallen leaves of 0.4 normal : in leaves apparently 1 year old, 0.006; and in leaves aboul 2 years old, \ conditi f great interest was found in one of these piles of leaf mold which was several years old. li was mellow and black, and the evidence of leaf structure had disappeared. When submitted to the phenolphthalein test it proved to be alkaline, and upon chemical examination it was found to contain 3.55 percent of lime (CaO). In this case decomposition had progressed so far, it is suggested, that the lime in the leaves, remaining constant in amount and probably having been changed to a more soluble state, had neutralized the remaining acidity. The material, then becoming alkaline, had pro- ceeded to decompose with greater rapidity, until a real mold had been formed. The condition here observed is doubtless the same a- that which occurs in the drained bog, < already in a state of remarkable fertility, is becoming increasingly alkaline Here allusion may he made to another phenomenon, (hat of the occurrence of the swamp blueberry and certain other plants, such a- the purple lady's-slipper {Cypripedium acaale) and the swamp honeysuckle {Azalea nndifora), in two lands of -it nation- one a peat bog, the other a sandy, w ell drained, and often dry upland. The favorite explanation of this phenomenon among botanists is that these plant- are naturally adapted to the drier -it nation and that in the bog they find a situation of "physiological dryness," or vice versa. A \ ' 1 1 i 1 * " the existence of physiological dryness in peat bogs i- not tioned, the explanation that a bog plant finds an upland situation congenial because it is dry certainly will not answer for the blue- berry. It- occurrence in these two habitats is dependent on the acidity of both situations. These experiment- have shown that no amount of dryness will make a blueberry flourish in an upland -oil if that -oil i- not acid. i : 1 1 Fob v< u\ i growth thi swamp blueberri requires v well- aerated soil. Conversely, rm swamp blueberry does noi continui in ictivi growth IN \ SOU - v I I i: v I I l> WITH v\ v I I I:. In its natural distribution the swamp blueberry does not grow in the lower, wetter type of bog. In a typical leatherleaf (Ckamae- daphm calyculata) bog, for example, the swamp blueberry is found 103 36 EXPERIMENTS IX BLUEBERRY CULTURE. either about the margin of the bog or on hummocks. In both these situations most of the roots of the blueberry bushes stand above the summer level of the water. When a bog has been built up by the growth of vegetation and the accumulation of the debris until the surface is above the summer water level, the swamp blueberry will occur generally over the bog. An examination of blueberry plants occurring on hummocks and bog margins has shown that such roots as extend beneath the per- manent summer water level bear few feeding rootlets or none at all. In one experiment it was attempted to grow blueberry seedlings in water cultures containing various dissolved nutrients. It was found that the roots made no new growth, that the new leaves were few and small, and that the general health of the plants was not good, whatever the character of the nutrient substances in the solu- tions. It was frequently observed also in the various oil cultures. particularly those in undrained glass pots, that the continued satu- ration of the soil with water reduced the root growth and enfeebled the whole plant. Continued excessive watering of potted blueberry plants was always found injurious. The observations just recorded must not be understood to mean that submergence of the roots is always injurious to the swamp blue- berry. In winter and early spring the water level of bogs containing blueberries often remains high enough for several months to com- pletely submerge the whole root system of the plants. On the lower end of the Wankinco cranberry bog near Wareham, Mass., are some native bushes of the swamp blueberry, the roots of which have been submerged in .") feet of water from December to May each year for about twenty years. These bushes when observed in September, L909, gave every evidence of vigor. Their twig growth was of good length and thickness, their foliage was dense and of a healthy color, their flowering buds for the next year were fairly numerous, and the bushes were -aid to be as productive of fruit as neighboring bushes on higher ground. It would appear from these facts that, while submergence during the dormant period is not injurious to the swamp blueberry, its roots dining their actively growing period must be kept above the water level so as to be well aerated. (10) Aeration conditions satisfactory for the swamp blueberry are preva- lent l.N SAND'S SOILS. The experiment cited above on this page showed that blueberry seedlings having their roots suspended in nutrient solutions failed to make a normal growth even though the solutions were suitably acidu- lated. This failure was ascribed to lack of aeration. In another experiment, described on pages 28 and •_".». it was shown that a similar nutrient solution when used to water a blueberry plant potted in sand produced a normal growth of both idol- and stems. The sand l'ur- L93 VTION CONDITIONS IN SAND AND PEAT. nished no appreciable nourishment and the only essential difference in the two cases was the abundant root aeration afforded by the sand culture. Sand i- therefore regarded as having been shown experi- mentally to furnish condition- suitable for soil aeration. In all the experiments in which blueberry seedlings were grown in sand cultures suitably acidulated, the root growth was good, even when very little nourishment was given the plant, and when \\-<\ with :i ueakl\ acid nutrient solution or with peat water the sand-pi plants always made a luxuriant root growth. In their wild state blueberries are especially prevalent on the sandy soils of i lie Atlantic Coastal Plain, as well as on sandy plain- and pine barrens in the interior. The drainage of such soils is good and their aerat ion is excellent. (11) Aeration conditions satisfactory for thi swamp bluebekri vri found I \ in: VINED I [BROl S PI VT. Kaltuia peal when in the original turf- or mat- i- full of -mall root- of oak. kalmia. and other plant-. In that condition it i- remark- ably porous and well aerated. Pieces of these turfs were used with great success in the bottoms of pot-, in place of crock-, to afford drain- age. For a potting -oil. however, kalmia peat can not easily be used until the -oil ha- been shaken from the ma-- of root- or ha- been rubbed through a screen. Even in that condition the fragments of leaves and rootlet- make the whole mass porous. A pot containing pure kalmia peat prepared by such rubbing often remains moist, yet well aerated, for day- at a time without watering. This moisture con- dition is due to two remarkable properties of peat, it- ability to hold a large amount of water, and the tenacity with which it clings to it. Kalmia peat taken from the interior of a -tack after it has remained several month- under cover ordinarily contain- loo per cent of water, computed on the dry weight of the peat. Even with this very high water content a peal -oil i- in a beautiful condition id' tilth. mellow, well aerated, and to the sight and touch apparently only moderately moist. Ordinary loam in a similar condition contain- only about I s per cent of water, and -and aboul 3 per cent. When saturated with water the moisture content of kalmia peat is about ,',i hi per cent of it- dry weight. The ability of peal to retain it- moisture depends in part on the gradual drying of the superficial layers and the consequent format ion of a mulch, lnit more particularly i- it dependent on a certain phys- ical affinity that peat possesses for water. The comparative strength of thi- water-holding power in different -oil- may he tested by sub- jecting them to a powerful centrifugal force, which tends to throw the moisture out of the -oil. The standard centrifugal force used i- a thousand time- the force of gravity. The percentage of moisture 38 EXPERIMENTS IN BLUEBERRY CULTURE. remaining in the soil after this treatment is known as the moisture equivalent of that soil. A test of kalmia peat made by Dr. Lyman J. Briggs, of the Bureau of Plant Industry, the originator of this method of measurement, showed a moisture equivalent of 14:2 per cent, as compared with about 30 per cent for clay, 18 per cent for loam, and 2 to 4 per cent for sand. From what has been said it is evident that fibrous kalmia peat has physical characteristics that allow the soil to be amply aerated. while at the same time holding abundant moisture for the supporting of plant growth. In this connection reference may be made to the influence of earth- worms on potted blueberry plants. Late in the winter of 1908-9 it was noted that among the blueberry seedlings of 1907, wjiich had been brought into the greenhouse, were several in which the growth was feeble, although others of the same lot were growing vigorously. It was noted also that the soil in the pots in which the feeble plants were growing contained earthworms, as evidenced by the excre- ment or casts deposited by them on the surface. The worms themselves were easily found by knocking the earth ball out of the pot, and the soil was seen to have been thoroughly worked over by the worms. It was supposed at first that the soil (a mixture of peat 8, -and 1, loam 1) in the process of digestion to which it had been subjected in passing through the alimentary canal of the earthworms might have become alkaline and for this reason injurious to the blueberry plants. When tested with phenolphthalein, however, the soil in the pots containing earthworms and feeble plants was found to be of the same acidity as that in the pots containing no earthworms and with vigorously growing plants. Furthermore tin 1 fresh casts themselves were of a similar degree of acidity. The texture of the soil, however, in the pots containing worms was very different from that in the others. It was plastic, very fine grained, almost clayey, the organic portion having been very finely ground evidently in passing through the gizzard and other digestive apparatus of the earthworms. The aeration of the soil in this condi- tion must have been far poorer than in the coarser soil containing a large amount of leaf fragments not worked over by worms, and it may be that the difference in growth of the blueberry plants was due to the difference in aeration. It i> not by any means certain, however, that the plants in the pots containing earthworms may not have been injured directly through (lie eating of (heir rootlets by the worm-. (12) AlCKATION CONDITIONS SATISFACTORY FOR Till SWAMP BLUEBERRY A.RE FOUND IN MASSES hi LIVE, MOIST. BUT NOT SUBMERGED SPHAGNUM. In some swamps the water level remains permanently above the general surface of the ground. \M»en the swamp blueberry occurs L93 DERATION CONDITIONS IN SPHAGNUM. 39 in such situations ii grows on hummocks the summits of which stand nbove the water during the growing season. Unless the water level [s extremely variable or the ground is densely -haded, these hum- mocks are usually covered with a cushion of live sphagnum moss. Ii is a peculiarity of t hi- moss thai ii absorbs water \\ iili great avidity; indeed, sphagnum is one of the most absorbent substances known. If one end of n nearly dry branch of sphagnum is brought into contacl wnli a little water, the whole branch becomes wet almost instantly. The water rushes along with marvelous rapidity through the cells of the plant and especially through the interstices between the minute overlapping leaves. The white air spaces between the half dry leaves flash "in of existence one after the other like candle flames in a gust of wind. The same ability to absorb water is characteristic of masses of tin- plant. If the lower part of a cushion of sphagnum is in contact with i'vi'c water the fluid is conveyed from stem to branch and front plant to plant in sufficient amount to render the whole mass a- wet as a sponge. When one squeezes a handful of such moss taken perhaps a foot or more above the source of moisture the water runs out in streams. A -ample of live sphagnum with less moisture than usual but -till with enough to maintain itself in a growing condition was found to contain 991 per cent of water, computed on the dry weight of the sphagnum, while saturated live sphagnum carried 1,005 pet- cent of water. On the basis of it- dry weight, therefore, sphagnum contain- about ten times as much water as peat, which it-elf contains about six time- a- much a- ordinary loam ami about thirty-five times a- much a- -and. The innumerable extracapillary air -pace- between the branches of sphagnum plant- and between the plants themselves furnish good aeration, even when the individual branches are saturated with water. When the moisture i- less the aeration i- -till better. The cushion of sphagnum on a hummock tend- to build itself up by the gradual process of growth and decay to the maximum height to which it can con\e\ the large amount of water required for its growth, and an increasing degree of aeration i- found from the water line upward. II' the sphagnum cushion on a blueberry hummock i- examined the whole ma— will he found interlaced with the minute rootlets id' the blueberry, far above the level of the nnderh ing soil. The conditions • 'I permanent moisture and thorough aeration found in these sphag- num cushions seem to be almost ideal for the development of blueberry roots. It must not he assumed that the vigorous growth of blueberry root- in sphagnum i- due to anj high nutritive quality of the sphag- num it-elf. Such a conclusion would be erroneous. When set out in sphagnum and watered with tap water, blueberry plant- remain healthy and develop a ven large i<>>\ system, but the stems do not 193 40 EXPERIMENTS IK BLUEBERRY (TLTURE. grow as luxuriantly as when the plants are in a peat soil. From experiments with the growing of blueberries in sand watered with peat water it is known that such water furnishes the food materials necessary for vigorous growth. It is reasonable to conclude, there- fore, that the chief nourishment of a blueberry plant growing on a pure sphagnum hummock comes from the bog water sucked up by the sphagnum and not from the sphagnum itself. PECULIARITIES OF NUTRITION. (13) The swamp blueberry is devoid ok root hairs, the minute organs through which the ordinary plants of agriculture absorb their moisture and food. The structure of the rootlets of ordinary agricultural plants may be understood by reference to figures 11 to 13, which illustrate these organs as they occur in a wheat seedling germinated between layers of moist blotting paper. Attention is directed particularly to the Fig. 11. — Root of a wheat plant, showing die root hairs. (Natural size.) Fir,. 12.— Portion of a wheal root, with rool hairs. (Enlarged 10 diameters I FIG. 13. — Tip of the root hair of a wheat plant. (Enlarged 1. I diameters.) root hairs. It will be observed that the wall of the root hair is very thin, appearing in optical section as a mere line with barely measur- able thickness, even when highly magnified. Furthermore, the sur- face area of the root hairs is many times greater than that of the root itself. The chief function of these root hairs is to absorb for the use of the plant the soil moisture and the plant-food materials dis- solved in it, a function which the root hairs are enabled to perform with great efficiency because of the two characteristics just men- tioned — their large surface area and the thinness of their walls. The rootlets of the blueberry are remarkable in having no root hairs whatever, as may lie seen by reference to figures 1 I to Hi. The walls of the superficial, or epidermal, cells of the rootlets are thick. measuring 0.00005 to 0.0001 of an inch ( L.3 to •_'.:• ft,), while the walls of the root hairs of wheal are one-fourth to one-sixth as thick, so thin, in fact, that they could be measured only with difficulty 193 l;i Dl I I l' ABSORPTIVE Si R] \< I 0] BLUEBERRY ROOTS. II even when enlarged 5,900 diameters. Notwithstanding the fact, therefore, thai the bluebern roots are fine and numerous, their actual absorptive capacity would appear to be small, in consequence of the absence of root hail-. It is found by a computation thai a sec- tion of a blueberry toot let having no root hairs presents about one tenth the absorp- tive surface of an equal area of a wheat rootlet bearing root hairs, and the thick- ness of the surface membranes in the wheat i- certainly not more than a quarter fig. it. Root of a biu< that in the blueberry. Furthermore, the plant < Natllralsize > blueberry rootlet grows only about 0.04 inch (1 mm.) a day under favorable conditions, while the wheat rootlet often grows twenty time- as fast. In all this provision for rapid food absorption in the one plant and retarded absorption in the other we find a reason for Pro. l" Bool of :\ blueberry plant. (Rnli i ii diameters. > Fig. 16. Blueberry rootlel i Enlarged 100 diameters. I the comparatively verj slow rate of stem growth thai characterizes the blueberry plant. The importance of -low root absorption and the danger to which these plant- would be subjected if their roots absorbed water rapidly are discussed on page 50. 103 42 EXPERIMENTS IN BLUEBERRY CULTURE. The young rootlets of the blueberry before they branch are ex- ceedingly slender, varying from 0.002 to 0.003 of an inch (50 to 75 fi) in diameter. This makes them very susceptible to actual drying and they are easily killed by it. This characteristic has an important healing on the treatment of these plants when in pots. The matter is discussed on pages 65 to 67. (14) The rootlets of healthy plants of the swamp blueberry are inhab- ited BY A FUNGUS, OF THE SORT KNOWN TECHNICALLY AS AN ENDOTROPHIC MYCORRHIZA. As already stated, the ultimate rootlets of the blueberry are very fine, their diameter varying from 0.002 to 0.003 of an inch (50 to 75 ft). In rootlets of the smaller size about three rows of epidermal cells are visible in a lateral view, in the larger rootlets about five rows. In a newly grown rootlet not contaminated with soil particles these epi- dermal cells, and, indeed, all the underlying cells as well, are as trans- parent as glass, and were it not for the difficulties due to the refrac- tion of light the examination of the contents of the cells would not be difficult. As a matter of fact the study of the contents of the live cells is difficult, their intelligent examination requiring the use of an oil immersion objective and microscopic enlargements of 1,000 to 1,500 diameters. The darkened window installation for a microscope, devised by Dr. X. A. Cobb, of the Bureau of Plant Industry, and used in his laboratory, has been found almost indispensable in this work. (lean rootlets may be procured readily from active blueberry plants in the open spaces between half-rotted leaf blades, in clean sand, in live sphagnum, or at the outer surface of the ball of soil in earthen pots. Rootlets taken from live sphagnum are especially clean. They are conveniently studied when simply placed in water on a microscope slide under a thin cover glass held in place by a ring of paraffin. Ordinarily the only thing visible in one of the live epidermal cells is the minute cell nucleus lying close to (he cell wall. The protoplasmic membrane lining the cell is very thin and is invisible except where it is thickened to envelop the nucleus. The remainder of the cell is tilled with the colorless cell sap. An examination with medium en- largements will show some of the cells faintly clouded in appearance. A higher power, such as is afforded by a 2-mm. oil immersion objec- tive and a l'.'-niin. eyepiece, with proper illumination, will resolve the cloudiness into a mass of fungous threads, or hyphse. These may he few. making only two or three irregular turns about the interior of the cell, as occasionally found, or they may be more numerous, even occupying the whole sap space, as shown in figure 17, in a dense knot "The spelling mycorhiza is also in good standing and is used in many German, English, and American botanical works. 193 ftOOl FUKGUS 0] mi B] I i Bl RRY, I.; of interwoven and irregular snakelike coils. These hyphae arc aboul 0.0 16 i" 0.1 L2 of an inch ( L.5 to 3 fi) in diameter. On the onici- surface of the cells containing these fungous threads others of similar or a little greater thickness may be observed. Some tin it-^ thi'v are transparent and their detection requires the same high power of ili>' microscope as do those in the interior of the cells. Sometimes, however, these exterior threads have a pale-brown color and arc then readily seen. Their surface is smooth, devoid of mark- ings of anj kind. Ordinarily the thread wanders loosely along the sur- face of the root gn ing off an occa sional branch and having an occa- sional septum. Sometimes the threads and their branches maj form an open network about the rootlet. but they never form a dense sheath of hyphae such as is characteristic of the mycorrhiza of t he oak. The connection between the exter- nal and the internal hyphae is not ea-\ i.i see at a single observation, for the passage of the hyphae through the eell wall i- rarely caughl in op- tical section, and even then a clear observation is usually rendered diffi- cult because of refraction. A very clear case, however, was observed in a runt let of laurel (Kalmia latifolia),a shrub which ha- a mycorrhiza! fun- gus similar to that of the blueberry. A drawing of that specimen is shown in (inure I s . The passage of the fungus through the cell wall may frequently lie ob- served in the blueberry by first focus- ing on the external hypha at a point where it appear- to have a lateral hump or a very short branch, and then focusing slowlj downward. In thi- wax one pa se from the external to the internal part of the fungus, having had some portion of the intervening hypha continuously in view. The hypha always appears much constricted at the point where it goes through the cell wall. Thi- fungus is of the type named bj Frank in 1 vv 7 an endotrophic mycorrhiza to distinguish it from an ectotrophic mycorrhiza, such L93 Pig. it. Mycorrhiza! fungus of a blue- berry plant densely crowded In two epidermal cells of the rool . i En- larged aboul 1,2 Ilami 44 EXPERIMENTS IN BLUEBERRY CULTURE. as occurs on the roots of oaks. In the latter type of mycorrhiza the hyphse of the fungus form a dense sheath around the rootlet, com- pletely shutting it off from direct contact with the surrounding soil. The loose hyphse on the outside of the sheath resemble root hairs and it is supposed to be a part of their function to absorb soil mois- ture and transmit it to the oak rootlet just as root hairs do. It has not yet been possible, for want of time, to study the life history of this mycorrhiza! fungus of the blueberry. There i-. how- ever, a clew to its identity in the work of Miss Charlotte Ternetz, Ph. D., described on page !'.». The experiments thus far made do not warrant a supposition that any good peat soil requires inoculation with the mycorrhiza! fungus before blueberry plants will grow well in it. The fungus appears either to he al- ready in the soil or to accompany the seeds when they are sown in it. (15) The mycorrhizal fungus of the .sWAMP BLUEBERRY Al'PI \i;s TO HAVE Nu INJURIOUS EFFECT, BUI EATHEB \ BENEFICIAL EFFECT, UPON Till'; BLUE- BERRY PLANT. The epidermal cells in which the mycorrhiza] fungus occurs are not swollen nor distorted, nor do their contents collapse or show any of the other effects usually produced by pathological fungi. They appear to differ in no respect from other epi- dermal cells of the blueberry rootlets. In rapidly growing rootlets the fun- gus seems not to be able to keep pace with the rootlet itself and may not occui- for a considerable distance bach from the growing tip. The fungus-filled cells ordinarily are most numerous on certain small, short, and crooked lateral rootlets the growth of which is slow. When root growth of a vigorous plant i< retarded or becomes even stagnated, the fungus may invade the epi dermal cells to the very apex. Sometimes half the cells in such a rootlet are gorged with fungi, yet the delicate cell walls --how no displacement or distortion. There is no indication whatever- that the fungus causes any pathological disturbance or is in any way obnoxious to the plant. On the contrary, the uniformity with L93 Fig. is. — Mycorrhiza] fungus of Kal- niin latifolia in an epidermal cell of the root: a, Cell walls ; b, external hypha? of the mycorrhiza! fungus; c internal hyphse; n healthy plants and its frequent absence or scarcity on sickly plants are Fad suggestive of :i bene- ficial influence. The nature of t hi^ beneficial influence is discussed en pages I s to 50. (16) THl m ii> n \ 1 -i SOILS IN H II li II l III SWAMP BLU1 . ii:i\ i s \i;i DE- FICIENT IN "available" nitrogen, although containing largi amounts hi " Mi\ AVAILABLE " NITBOG1 N. Ordinai'y agi'icultural plants absorb their nitrogen from the soil in the form <>l' nitrates. Whether any arc able i<> utilize directly other forms "I' nitrogen, particularly ammonia nitrogen, has been the subject <>!' much experiment and of discussion by many authors. It is tine in general, however, that the common plants of agriculture when their other food requirements are satisfactory make their growth in direct proportion to their ability to secure their nitrogen in the form of nitrate-. For this reason the processes of agriculture are largely devoted to the securing and maintenance of conditions that will bring about the transformation of nonavailable nitrogen into nitrates. Soil- in which tin- can not lie done without great expense in proportion to their productiveness are generally con- sidered poor. The acid -oils in which wild blueberries thrive an- always looked upon as infertile in their natural -tale, and unless these . 17. i Thai kalmia peal, the -oil found in these culture- to he most suc- cessful for blueberries, i- deficient in nitrates, although containing an abundance of nitrogen in other form-, is shown by the following mi rogen determinal ion : rOTAl NITROGEN IN KALMIA I'l. \ I'. ( Determinations made by .Mr. T. < '. Trescott.) Sample. I o IVr cenl 1. i>; 1. 1. Is in 1. 1. to 12 Average of total alt rogen 1. iii IlKi 46 EXPEBIMENTS IN BLUEBERRY CULTURE. NITROGEN IN KALMIA PEAT IN THE FORM OK NITRATES. (Determinations made by Mr. Karl I'. Kellerman.) Sample. Per cent. 7 0.0012 8 .0022 » . . 0008 10 .0013 11 .0025 12 .in i« is Average of nitrate nitrogen .0015 (17) The deficiency of available nitrogen in the acid peaty soil in which the swamp blueberry grows best is due to the inability of 1111 nitri- fying bacteria to thrive in such a soil because of its acidity. Iii order to understand the conditions antagonistic to nitrification which exist in good blueberry soils it is necessary first to discuss the source and transformation of nitrogen in ordinary soils. The available nitrogen in the soil, such as is absorbed by an ordi- nary plant, is commonly derived, unless fertilizers have been ap- plied, from the decomposition of the humus contained in the soil, and the humus is itself a product of the decomposition of plant and animal remains. These remains consist ordinarily and chiefly of the partially rotted leaves, stems, and roots of plants. In the older agricultural literature the name humus was applied to a particular kind of soil which is more properly covered by the terms vegetable mold, leaf mold, and woods mold. (See |>. 24.) Later the application of the word humus was restricted to that por- tion of a soil consisting of the plant and animal remains, in whatever stage of decomposition. The proper designation of these remains is, however, organic matter. In the sense just described the word humus is still frequently used, but not with correctness and precision. Humus, as now understood by agricultural chemists, represents a stage in the decomposition of organic matter in which the cellular structure has wholly disappeared and (he original substance IS or at -nine stage has been entirely dissolved. Since it is often necessary to allude to organic matter in the earlier stage, as distinguished from organic matter as a whole, which in- cludes the humus stage as well, the term cellular organic matter, or. more simply still, cellular matter, is suggested as a convenient desig- nation. In cellular matter the cellular structure of the animals or plants still remains and may be detected either by the eye or by the microscope. Humus, which is a complex mixture of diverse substances, does not ordinarily exist in the soil in a dissolved condition, but i- usually combined with lime or magnesium. The resultant compounds, often indiscriminately blanketed under the names calcium ami magnesium 103 BUMUS THE USUAL SOURC] 01 NITRATES. 1 i humate, are not soluble in water, but form :i usually black precipitate, w hull gi\ es a dark color to the -nil. To extracl it- humus a -oil is first washed with dilute acid, by which the lime, magnesium, or other humus precipitating substance is dissolved and leached away. The humus itself is then removed from the -"il l>v long-continued washing with a weal; solution, commonly I per cent, of ammonia. Upon the application of this treatment to kahiiia peal an inky-black extract is secured. When this is evap orated to dryness the residue i- a black substance which when scraped from the dish resembles coal dust or, even more closely, burned sugar. This substance is one of the forms of humus. It absorbs water read- ily, assuming the texture of thin jelly. It has ;i somewhat sooty odor and taste. It dissolves in water, the solution being acid in reaction. A liter of water in which had been dissolved a gram of humus ex tracted from kahnia peat showed when tested ;i 0.002 normal acidity. Such ;i solution is Mack unless viewed in a thin layer, and when ill luted tn 10,000 c. c. it has a brown color similar to that of ordinary cider vinegar. II' lime is added to the solution the humus unite- with it and is thrown down as a black precipitate, leaving the liquid clear. As stated in the preceding paragraph, it is in such a precipitated and neutral or alkaline form that humus ordinarily occurs. The charac- teristic brown color of the water in bogs indicate- an acid condition. the presence of humus in solution, and the absence of soluble lime. The process of decomposition by which cellular matter i- trans- formed into humus, in which the cellular structure has entirely dis- appeared, is know n as humificat ion. Humus contain- nitrogen, but the nitrogen is not in the form of nitrate- and therefore can not be assimilated by ordinary plant-. The transformation of humus nitrogen into nitrates occur- during a further process of decomposition known as nitrification. The nitrification of humus is brought about by certain bacteria which, growing in the humus-laden soil under suitable conditions, produce first ammonia, then nitrites, and then nitrate-. In artificial culture-. In addition to proper condition- of temperature, moisture, and good aeration, these nitrifying bacteria require for vigorous growth a neutral or slightly alkaline medium. In a distinctly acid medium the nitrifying bacteria gro^ little or not at all. In order to ascertain the degree of nitrification, if any, taking place in kalmia peat, a -eric- of nitrification tests of this material was made by Mr. Karl I-'. Kellerman. These tests showed that neither in fresh peat nor in peat rotted for three month- was nitrification in progress, but when the acidity of the peat was neutralized l>\ the addition of lime nitrification l tega n, 193 48 EXPERIMENTS IN BLUEBERRY CULTURE. ( 18) From the evidi \< i vi hand the presumption is that the mycorrhizal I CJNGTJS 01 nil SWAMP BLUEBERRY TRANSFORMS THE NONAVAILABLE NITRO- GEN OF PEATY SOILS INTO A FORM OF NITROGEN WAILABLE FOR THE NOUR- ISHMENT OF THE BLUEBERRY PLANT. It is a well-established principle of plant physiology that (with the possible exception of a few bacteria) those plants which contain no chlorophyll, the green coloring matter of leaves, are unable to grow with mineral nutrients alone, since they are unable to manufacture their own carbohydrates. Plants without chlorophyll, including the fungi, are dependent for the fundamental part of their nourishment on the starch or other related carbohydrates originally elaborated from carbon dioxid and water by the chlorophyll-bearing plants. They also differ from the higher plants in being able to supply their nitrogen requirements directly from organic nitrogen compounds. Fungi may be directly parasitic on a chlorophyll-bearing plant, as in the case of the mildew fungus of rose leaves, or they may grow on substances derived from chlorophyll-bearing plants, such as bread or jelly. Fungi are particularly abundant in the decaying vegetable matter forming the leaf litter of a forest, even though this litter may be distinctly acid in its chemical reaction. They are known, indeed, to grow luxuriantly on vegetable remains containing no nitrates and of such acidity that nitrification, or (he conversion of the humus nitrogen into nitrates by means of bacteria, can not take place. That the mycorrhizal fungi, like other fungi, are able to extract nitrogenous food from the nonnitrified organic matter with which their external portions are in contact is a reasonable supposition. It is furthermore a reasonable supposition that the blueberry plant is able to absorb nitrogenous material from the internal portion of its mycorrhiza; for we know that the clover plant is able to absorb nitro- gen under essentially (he same conditions from the nitrogen-fixing bacteria growing in its root tubercles. To establish by direct experiment the ability of the mycorrhizal fungus of the blueberry to act ii. accordance with the supposition outlined above, the fungus should be separated from the plant and grown by itself in suitable nutrient media. Preliminary trials were made to isolate the fungus, but without success, and a lack of time has prevented thus far the pursuit of that branch of the experiments. (19) ll IS POSSIBLE THAT THE MYCORRHIZAL FUNGUS OF THE SWAMP BLUEBERRY TRANSFORMS THE FREE NITROGEN OF THE ATMOSPHERE INTO A FORM OF NITROGEN SUITED TO Till LSI ul THE BLU/EBERRY PLANT. The fact of the fixation of atmospheric nitrogen by the bacteria inhabiting the root tubercles of clovers is now well known, and we are able to understand how the abundant nitrogen of the air. unavail- 193 •nil ^.TMOSPHER] \s \ SOURCE OF NITROGEN. 49 able for the direci nutrition of ordinary plants, is made available for the use of leguminous crops. It is nol so generally known thai there are in soils certain sp< of bacteria noi connected with the roots of plants which also po the faculty of taking up the nitrogen oi the air and making ii over into plant food. 'The extent of the distribution of these organisms and the an n< of nitrogen fixation effected by them are not fully known. hui the facl that such action does take place and that the bacteria causing it occur in many localities has been well established by the experiments i !' several investigators. The bacteria of this class most fully investigated are Clostridium pasteurianum,, Azotobacter chro- »///. and several other species of this hitter genus. It has been shown also that certain fungi, such as Penicillium glaucum-, possess this same power of assimilating atmospheric nit rogen. After the writer had discovered the mycorrhizal fungus of the swamp blueberry in December, L907, and while he was making obser vations on it. his attention was called to the work of Miss Charlotte Ternetz on the mycorrhizal fungi of certain related European plants. Miss Ternetz published in L904 a paper" in which she made the pre- liminary announcement that a fungus isolated from the root- of the European cranberry (Ox\ oxycoccus) had developed pyenidia and i hat t he my eel i um produced from spores from these pyenidia when grown ina nitrogen-free nutritive solution, bui with full access to air, showed upon analysis that it had assimilated free atmospheric nitro- gen to the extent of 0.6 per cent of the dry weight of the mycelium. 'The fungus consumed only one-eighth as much dextrose in assimi- lating a given amount of nitrogen as was consumed by Clostridium ■ "',,,. Similar hut not identical fungi were isolated from other related plants. In 1907, in a more detailed account of her investigations, 8 Miss Ternetz described, a- new species of Phoma, live pyenidia-bearing fungi bred from the roots of the European cranberry (Oxycoccus oxycoccus), the marsh rosemary (Andromeda polifolia), two species of heather ( Eri< <' t, tralix and E. < ai i>, a >. and the mountain cranberry (Vaccinium vitisidaea). She was unable to demonstrate absolutely that these fungi were identical with the endotrophic mycorrhiza of the host plants because i 1 > it was extremely difficult to observe the fungous threads of the internal mycorrhiza grow through the cell wall of the rootlets into the culture medium without, and (2) be- rernetz, Charlotte, Ph. I >. Assimilation des atmosphiirischeu Stickstoffs . Cleber die Assimilation des atmosphtlrischen Stlckstoffes l' them i- out of the question. The mure impor- tant results of these experiments may be presented, however, in an accounl of the seedlings of 1908. the latest thai have been grown for an entire year, with allusions in the experiments of other years whenever additionally useful. The parent plant of the seedlings of 1908 is described on page s \ M by •"> inches. inside measurement. After crocks | ia d been placed over the drain age holes the bottom was covered to a depth of about an inch with 193 52 EXPERIMENTS IN BLUEBERRY CULTURE. kalmia peat in fibrous form to insure good drainage. Over this was placed the finely sifted soil of the seed bed. trodden down with the whole weight of the body, the total thickness of the soil and drain- age being 2.5 inches. The soil of the seed bed in this instance was a mixture of the following, each rubbed through a wire sieve with ,',.,-ineh square openings: Kalmia peat . 8 parts by bulk. Sand 2 parts by bulk. Live sphagnum 2 parts by bulk. Loam 1 part by bulk. While this mixture gave good results, certain modifications in the direction of simplicity have been found equally satisfactory so far as growth is concerned, and more satisfactory with regard to the ease of transplanting. These changes involve the omission of the loam, which from other experiments is now regarded as never advanta- geous and sometimes actually injurious, and the omission of the sphag- num, which, although a good moisture-holding and aerating me- dium, appears to be superfluous in a peat and sand mixture. The sphagnum also interferes somewhat with the clean pricking out of the seedlings in the first transplanting. From experience with vari- ous other seedlings of blueberries a mixture of 2 parts of finely sifted kalmia peat to 1 part of sand is regarded as satisfactory and preferable. The peat should be well rotted and the sand clean and free from lime. This matter is more fully discussed on page 60. After the seed bed had been prepared, as already described, the dry seeds were scattered upon it and covered with about an eighth of an inch of the same soil lightly sifted over it. The surface was then sprinkled with water from a sprinkling pot provided with a very tine rose. So far as moisture is concerned the ideal condition of the seed bed is that the soil should lie just damp enough so that it shall not be- come dry on the surface. The drying of this peat is indicated by a conspicuous color change, from dark brown to light brown. If ex- posed directly to an ordinary greenhouse atmosphere, the tendency of the seed-bed surface to become dry will necessitate frequent ap- plications of water, and the bed will be in danger of repeated periods of sogginess. These conditions may lie very much improved by cov- ering the ilat with panes of glass. An opening about an inch wide should be left at either end to permit the circulation of air over the seed bed. This ventilation will prevent the excessive accumulation of moisture in a stagnant atmosphere and will also prevent over- heating on sunny days, both of which conditions are injurious to seedlings. A flat thus covered may not require watering for inter- vals of several days. The advantages of the glass covering are par 193 Bui. 193. By, . u. S Dopt. of Agi Plate VI. 9^ V * «£^/@ F 1.— Swamp Blueberries from the Parent Bush of the Seedlings of 1908. ed after remaining nearly a yi nlin, and the illustration not show ilu-ir maximum si/r and plumpness. (Natural size, i Fig. 2.— Seeds of the Swamp Blueberry. nr-o'.l In di GERMINATION I >l Bl I i Bl Rm S] I DS. 53 Fig. 19.- Section of ;i blue berry seed : . thirty-seven days after seeding, and eon- tinned for more than two months. In other seedings of this and the closelj related I • 1 1 it I lerries known as Vaccinium atrococcnm and V. pallidum, germination has begun in as short a period as twenty five days. This slowness of germination might be considered merely a feature <>!' the genera] sluggishness of growth in these plant-. It is in fact, however, due to a much more specific cause. The food stored in the seed for the nourishment of the plantlet is not located in the cotyledons, as in the bean or pea. for example, but it lies in a mass called the endosperm, quite outside the embryo, t Sec fig. L9. 1 It re quires several week- for the minute embrj o, feeding on t he large mass of surrounding endosperm, to grow to sufficient size to burst open the seed coats. Until the embryo has attained such size it is physically impossible for the -eed to ger- minate. When the seedlings had straightened themselves out they were about 0/2 to 0.3 of an inch (5 to 8 mm.) high and the newly expanded cotyledons about 0.0G of an inch (1.5 mm.) long. (See fig. 20.) Wit Inn a few day- the first foliage leaf began to appear between the cotyledons about 0.06 of an inch (1.5 mm.) long. (See fig. 20.) inch i Hi to 15 nun. i high, the erect unbranched stem bearing four or five foliage leave-, and the cotyledons having expanded to a length of 0. 12 of an inch (3 mm. >. i See fig. 21.) ia:i Kn;. 20. — Blueberry seedlings In th< ■ ledon stage a, Befoi el ion of b, :n the beginning of the development of the flrsl foliage ' Enlarged 2 diameters, i 54 EXPERIMENTS IN BLUEBERRY CULTURE. Although the leaves of the parent plant had entire margins, the leaves of the young seedlings were invariably serrulate. It was only after the plants were several months old that any of the branches began to produce leaves with entire margins, and some of the seedlings from this parent give promise of permanently retaining the serrulate lea l' character. ( See p. 82.) (21) The seedlings are first transplanted at the agi <>i aboot six weeks, when they are approaching an inch in height. On October 24 the first transplanting was done from the mh^\ flats of 1908. A new flat was filled to a depth of '2 inches, trodden down hard, with the following mixture: K .- 1 1 1 1 1 i : i peat, rutted for several months and rubbed through a quarter-inch sieve 8 parts by bulk. Sand, coarse, washed lpartbybulk. Loam, clayey, finely sifted lpartbybulk. This soil mixture was used as the result of experience of the two preceding years. From a few experiments made in the winter of L906— 7 it had been found that a mixture of equal parts, by bulk, of peat, sand, and loam was decidedly superior to loam and manure or to sand, sphagnum, and loam. In the winter of 11)07-8 it was found that the amount of sand and loam could be re- duced with distinct advantage, and as a result of the experiments then made many of the cultures of 1908-9 were grown in the mixture described above (peat 8, sand 1. loam 1). The retention of the loam was due to an idea that this ingredient would furnish some necessary mineral nutrient not furnished by the peat. From an ex- periment made in the summer of 1909. however (p. 69), ii was found that under the System of handling the pots described Fig. 21.— Blueberry seedling ._ . , , . i ni six weeks old. with five <»' page •>, large plants repotted in a peat foliage leaves. (Enlarged 2 S(! j] with no loam whatever made a better diameters. > ,1^1 1 ■ growth than those potted in a peat con- taining a tenth part of loam. There is some reason, therefore, to suspect that loam, even in such a small quantity, may be slightly injurious, and more reason to suspect that it may be superfluous. Experiments intended to throw light on this question arc now in progress. In the soil of the Hat. prepared as described above, 80 plants were set "_ ; inches apart. They were pricked out of the seed bed and set 193 Till. \ I \l i \ i OF THE i'OUNG SEEDLINGS. .'.."> in the new soil l>\ means of a -mall dibble. These plants were halt' to three- fourths of an inch high and had three to six true leaves. It i- believed that a spacing of 2.5 inches in the flat is better than ■_' inches, as the plants have a little more room and the 2.5-inch square of earth is a very convenient size when the next transfer is made into I inch pots. From this time on during the winter the plain- were kept in a cool greenhouse in which the night temperature was •">•"> to t'>o F.. and which was given a large amount of ventilation. The day tempera- ture reached ordinarily 65 to TO F. It was found that a house with a nighl temperature of l<> I*", and a day temperature of 60 F was too cold for such seedlings, as they made almost no growth at all. In a warm house, 65 to 70 at night and 80 to 90 F. in the daytime, blueberries grow fairly well, but they are much subject to injury by red spider (Tetranychus bimaculatus) , and their new growth while sufficiently extensive does not appear so robust as in the 60 to To F. house. For the first few days the newly transplanted seedlings were shel tered from direct sunlight. Later, however, they were given all the sunlight possible. It was found that during the winter, when well established in a suitable soil and under proper moisture conditions, the plant- greys better when they received the fullest sunlight that the greenhouse afforded. This statement applies t<> the plants in all stages, whether in a seed bed or alter the first transplanting or in larger puts. In watering, the plants should be kept "on the dry side," as gar doners say. Water may advantageously be withheld until the surface of the -oil is dry. hut this condition should not be allowed to extend lo a depth id' more than aboul an eighth of an inch. Then a rather thorough watering should be given, which will carry moisture to the bottom ) the "stagnation," or stoppage of expansion of the uppermost leaf rudi- ment : and i i i the purpling of the older lease-. A- these phenomena when persistent have been much utilized in these experiment- as warnings of the existence of condition- antagonistic to growth and a- they may he of similar assistance to other experimenters, a de- scription of them will he given. 193 56 EXPERIMENTS IN BLUEBERRY CULTURE. The withering of the tip includes the uppermost leaf rudiment and the growing point of the stem inclosed within its folded base. The tissues turn brown and become dry, and the growth of that axis is terminated. The resumption of growth from such a stem, if it occurs, takes place through the formation and expansion of a bud in the axil of the leaf next below the withered one. This withering of the tip is readily distinguishable by its color from a partial blacken- ing of the uppermost tender leaves which sometimes occurs, appar- ently a pathological disturbance of a temporary character and usually not affecting the growing point of the stem itself. The brown wither- ing of the tip seldom takes place when the leaf rudiment involved in the withering is more than 0.1 inch (2.5 mm.) in length. When longer than that it usually keeps on expanding. This withering of the tip- has been almost wholly prevented when the shock of transplanting was rendered as light as possible by suitable precautions, including (a) a soil in perfect condition for the nutrition of the plants, espe- cially that in which the peat is well rotted (p. CI) ; (b) the transfer of the plants to their new bed without injury, especially without destroying any part of the roots; («?) the shading of the plants from direct sunlight for two weeks or more, until their new root growth is well established, and their subsequent gradual adjustment to full sunlight; and (d) the holding of the transplanted plants in a warmer, moister atmosphere, about 65 c at night and 80° F. in the daytime. Whether or not this last condition had a real influence on the prevention of the tip withering is not definitely known. The stagnation of the uppermost leaf rudiment does not attract the inexperienced observer's attention so readily as its withering. With a little experience, however, it is easily detected. Ordinarily the leaves of a growing stem follow each other at a rather dose interval, so that by the time a half-grown leal' is ready to flatten out. from its boat-shaped folding in the younger stage, the succeeding leaf is com- monly a third or more the length of the one that is flattening (fig. 22). When stagnation occurs, however, the uppermost leaf rudiment promptly stops growing, usually at a length of 0.04 inch (1 mm.) or less, while the young leaf next below it goes on flattening and glow- ing to nearly its normal size. The end of the stem, therefore, shows a nearly full-grown flat leaf with a minute leaf rudiment at its base seldom more than a fifth and often not more than a tenth its own length. The purpling of leaves, to which allusion has been made, does not refer to the reddish translucent appearance of the growing twig tips. That i- the normal coloration in the blueberry, as it i-. for example, in the rose. The purpling now under consideration occurs in the mature leaves, which are normally green, and is of a dark shade. It is commonly accompanied by a conspicuous reddening of the leaf [93 PREVENTION OF INJUR! IN TRANSPLANTING. 57 veins. This purpling of the old leaves is evidence of a severe stop of growth and in these experiment? has been observed to I" caused by lov temperature, about In F. or lower, or by hick of nutrition from any cause, or, apparently, by poisoning. [f the soil into which young blueberry seedlings arc transplanted is suited to their growth, purpling of the old leaves seldom occurs, the e\ idence of the -hock of transplanting being confined to the po- sible withering of a few of the stem tips and the temporary stagna- tion of other-. In -nine transplantings no withering of tips occur-. During the period of cessation of stem growth after transplanting, the plant is by no mean- idle, for the roots, as shown in glass-pot cultures, continue to make new growth, and when this has sufficiently progressed stem growth is resumed. (22) Will N IBOl l UN WEEKS OLD \M> NEARLY TWO INCHES in HEIGHT THE SEEDLINGS BEGIN TO SEND OU1 BASAL BRANI HES. An important phase in the development of the seedlings of 1908 began on November 25, when one of the plant- commenced to out a branch from the axil of a cotyledon. At the expiration of another month 75 per cent of the plants in the flat had put out similar basal branches, and the remaining 25 per cent ultimately did the same. These basal shoots are of the highest im- portance in the economy of the blueberry plant, for they soon far out-trip the lir-t stem and become the principal seat of growth, until they themselves are over shadowed by later and -till more vigorous? basal shoots. The original stem of the seed- ling never develops into an ultimate main stem or trunk, but, as will be seen later (p. 58), stops growing while the plant is -till young, and afterward dies. It is this habit of sending up basal shoots thai makes the swamp blueberry a many-stemmed bush, nol a miniature tree \\ ith a single trunk. The development of basal shoots began when the seedlings had about 12 leaves and were about L.5 to 2 inches high. In this lir-t basal branching the number of branches varied from 1 to 3. Out of 73 plant- on which the branching was recorded 39 had 1 branch, 30 had ■_' branches, and I had 3 branches. The branches occurred in the axils of the cotyledon- or of one of the lir-t four lca\ es. Of the 39 plain- with 1 branch, 1 1 had the branch in the axil of a cotyledon. 17 in the axil of the first leaf, 8 the second, 2 the third, and 1 the fourth. Of the 30 plant- with 2 branches, II had both branch 193 I'm. 22. Normal t i|> ol in a blueberry seei a rged I dlatu the smaller figure natural 58 EXPERIMENTS IN BLUEBERRY CULTURE. the axils of the cotyledons, 13 had neither branch so situated, and 6 had 1 branch from a cotyledon axil and 1 from a leaf axil. Of the 4 plants with 3 branches. 3 had all 3 branches in the axil> of the cotyledons and the first leaf. 1 had a branch in the axil of a cotyledon and of the first and second leaf. Of the total 111 branches 46 were in the axil of one of the two- cotyledons, an average of •_':'> to each, 'M> in the axil of the first leaf, 20 the second, 7 the third, and 2 the fourth. In the order of the frequency of production of a basal shoot. therefore, the first leaf stands Hist, a cotyledon next, then the second, third, and fourth leaves, in order. While the exact location of the basal branches appears to have no special significance, the number of the branches does, for the habit of producing two or more branches i> a persistent one and such seedling> tend to produce diffuse plants with many and small stems and small stature, while the plants with the single-branch tendency are taller and have fewer and more, robust stems. The differences in general appearance caused by the two types of branching are well illustrated in figures 24 and 25, from photographs of two seedlings of 11)07 made at the age of 10 months. (23) When the seedlings are about four months old and about threk inches in height the growth of the original stem terminates. On January 5, 1909, the growing tip on the original stem of one of the plants withered. At that time this stem was about 2.5 inches high, had 14 leaves, and had 2 vigorous basal shoots about an inch in length. This withering differed in one important respect from the withering due to shock, described on page 50. In that case it was an ordinary leaf rudiment that withered. In the present case the withering was fore- shadowed by the development of a minute brad ( lie;. 23). This differed from the ordinary leaf rudiment in the absence of the glandular hairs characteristic of young leaves, and it remained small until the leaf next below it had become more than ten time- as long. Then the bract withered and the growth of the original stem was permanently terminated. The same de larged 4 diameters • the velopment went on in the other plants until smaller figure natural ;|( (|u , ( j ()f ., nH)lllh ,;;, per ,.,.„, ., 11( 1 j„ two months '.).'> per cent of the plants had terminated the growth of their original stems. In the individual plant the termination of growth on the original Stem took place after the basal shoot or shoots had reached a stage of 193 Fig. 23. — Bract ami young leaf al (lie end of the original stem in a blue- berry seedling. < En BRANCHING OF THE SEEDLINGS. 59 \ igorous development. Out of fifty-nine normal cases observed prior Lo the second transplanting of the seedlings, the Length of the new shoot, or when more than one the longest of them, at the time of termination of growth on the old stem varied from 0.4 of an inch to 5 inches, with an average of L.8 inches. It would appear that the Fig -i Blneberrs --i'iIUhlc with diffuse i-'u;. 25. Blueberry seedling of the type i.\i ( branching. This will become a with few branches The branch is more low, many-branched bush (One-third than twice as tail as the original main natural sizo.i stem. (One-third natural size. ) immediate cause of the termination of growth on the old stem is the diversion of food materials into the new vigorous growth. ( 'J I i Will \ I III PLANTS \i:i Willi I 1 l\ I MONTHS OLD AND FOVR TO SIX INCHES IN Ml l(. II I I III -i Mil POTTED IIS FOUR-INCH POTS in IES1 PEAT OR PEAT MlVllltl . ( )n February 17. when the plants were I to 6 inches high, they were transplanted into 1 inch pots in the -nine -oil mixture a- was used in the transplanting of October 24 (peal 8, sand L, loam I). A.s stated 19."! 60 EXPERIMENTS IN BLUEBERRY CULTURE. in the discussion of that transplanting, the plant- would probably have done somewhat better without the loam. In addition to the crock over the drainage hole, a mass of fibrous kalmia peat was placed in the bottom of the pot, filling it. when pressed down, to the depth of an inch or more. After cutting the soil in the flats into rectangular cakes, the plants were lifted and transferred to the pots with the least possible disturbance of the roots. Several experiments had been made earlier to ascertain whether at the first transplanting from the seed bed it is better to set the plants in flats or to put them in 2-inch pots, or thumb pots as they are more commonly called. It was found that when the plant- in thumb pots were set on a greenhouse bench they tended to dry out so rapidly that it was impracticable to keep them in the right con dit ion of moisture. They became so frequently too wet or too dry that their growth was interrupted and they were much inferior to the plants in the flat--. Other plants in thumb pots (PL VII). plunged in either sand, peat, or sphagnum, made about the same growth as the plants in the flats, but showed no uniform advantage over them, either while they were in the thumb pots or after a second transplanting. The labor of transplanting and of maintain- ing uniform moisture is somewhat greater in the case id' the potted plants. All things considered, in the original transplanting the use of flats is regarded a- preferable to 2-inch pots. It is desirable to consider at this time the exact qualities of the soils used in the potting mixtures. As already stated, it is regarded a- preferable to omit the loam. The sand should be free from lime, as most -and is. in fact. Ii should also be as clean as possible. If the only sand obtainable is mixed with clay, this should he removed by repeated washing in water. The condition of the peal should also be carefully considered, as shown by the following experience during the progress of these experiments. From the seedlings of L908 many series of trans- plantings were made on various day- in October. November, and December. In the latter part of December it was noticed that while in some of the transplantings the seedlings were growing vigorously, other cultures were not doing well at all. Many of the tip- were withered, over •_'.'> per cent in some of the culture-: the rest became stagnated and dark purple, and remained so for nearly two month-. All possible causes of the trouble having been eliminated except those due to (he -oil. the characteristics of the various soil- used were considered with care. At this time the writer was possessed of the erroneous idea that lime in the minutest quantities was very injurious to the blueberry (p. 20), and consequently it was sus- 19:j Bui. 193. Bureau of Plant Industry, U. S. Dept. of Agriculture. Plate VII. a o Bf > 1 X -. O i z ' O I At I SSIVI M M'l n "i fRESH PEA I . 61 pected 1 1 1 : 1 1 ilif sand was impure and contained lime. An exami- nation of the sources of the different kinds of sand used showed that lime could no! have caused the trouble. Finally, however, the various cultures were arranged by the dates of potting, and it was then found thai the purpled plants had all been potted after a certain date, on which a new lot of peat had been received at the greenhouses. The peat in the earlier cultures had been received in June and at the time of the first transplantings had been rotting for four months at a warm summer temperature. T1h> seedlings transplanted into this peat did uot lose their tip-, and growth was resumed almost immediately. The peat used after the middle of Nbvembei was freshly gathered, and it was in this fresh neat that the seedlings suffered as already described. It should be stated here, however, that by the end of two months these seedlings, which meanwhile had been making good root growth, began to make rapid top growth also and later overtook their competitors. Acidity tests of peat from the various cultures and in different - of decomposition showed a remarkable correlation between the. acidity of the peat and the behavior of the seedlings. In the fresh deleterious peat the acidity was excessive, varying from 0.03 to 0.046 normal. In the older peal in which the plants grew well the acidity was usually not in excess of 0.02 normal, in one case 0.024. Fresh peat rubbed through a quarter-inch sieve and showing an acidity of 0.034 norma] had lessened it- acidity to 0.02 normal after remaining in a moist well-aerated condition for three weeks in the warm air of a greenhouse. In view of these fact- the conclusion was reached that the deleterious effect of fresh peat is due to its excessive acidity. In the undisturbed peat of a kalmia thicket wild blueberry plants are often found growing luxuriantly. After this peat is stripped from the ground it becomes injurious, as has been shown, to blue- berry plants that are potted in it, this injurious quality being cor- related with an excessive acidity. The question arises, What ci this increase in acidity and in what particular part of the soil does it reside? It was at first suspected that the excessive acidity was located in the less decomposed upper layers of leaves which the roots of the blueberry plants in a wild state do not reach, but which, when the peat is rubbed through a sieve, go into the resulting mixture. The leaf layers to which reference is here made are not the uppermost, neail\ dry layers a year or less old, for these are removed in gather- ing the peat . la it the part iall\ rotted layers one t" two years old, such a- those shown in Plate IV. An examinati f such material showed that it was not excessively acid, but came well within the range of acidity beneficial to blueberry plant-. An acidity determination was then made of the root- in the peat. These are the roots, chiefly of oak and kalmia. that interlace the 193 62 EXPERIMENTS IX BLUEBERRY CULTURE. partly decomposed portions of the peat into mats or turfs. Their appearance in the upper part of those turfs is shown in Plate Y. figure 2. Taking some of these turfs, freshly gathered, the soil was all shaken from them, leaving only the " fiber," consisting entirely of these fine live roots. This fiber was allowed to rot for a few days, and an acidity test was then made. It proved to be 0.07 normal, an acidity far in excess of that which had. proved injurious to the blue- berry seedlings. The excessive temporary acidity of freshly gathered kalmia-peat turf and its consequent temporary injuriousness to blue berry plants are therefore attributed to the diffusion through the peat of the acids originating in the roots killed in the process of gathering tin- turfs. It should he added here that the acidity of the uppermost layer of undecomposed leaves a year or less old is very great, and that care should consequently he exercised to keep these out of the soil used. A test of dry. brown, newly fallen sugar-maple leaves showed an acidity of 0.i22 normal, and a mixture of the leaves of various species of oak in a similar condition. 0.4. Incidentally, attention may he called to the presumable efficiency of a mulch of such leaves in maintaining, by mean-- of its leachings, under the influence of the; natural rainfall, the acidity of the underlying more fully decom- posed layers, which without the addition of fresh organic matter would ultimately become alkaline. (See the account of an alkaline oak-leaf mold on p. 35. ) (25) Blueberry plants potted ln peat may bi made to grow mori bapidl^ if they auk watered oc< vsionali.y during the growing si \s<>\ with water from a manure pit. In the winter of 1907-8 pottings of seedling blueberries from seeds sown in August, 1S>07. were grown in various greenhouses of the Department. The most successful of these pottings consisted of 89 plants in a mixture of peat, sand, and loam in 3-inch pots. Two of these plants are illustrated in figures 24 and 25. It had been sup- posed that the superior growth of these plants was the result of specially favorable conditions of light, temperature, and watering, as indeed it was in part; hut in the following winter, during an inquiry about certain details of the handling of (his culture, the gardener in charge of the greenhouse in which the plants were grown admitted that during a portion of the spring, without consultation, he had given the pots an occasional watering with manure water. A.S manure when used with loam in the winter of 1906-7 had proved positively injurious to blueberry plants, its possible beneficial effeci when used in conjunction with peat seemed worth testing further. In the spring of 1!)0!). therefore, various cultures were watered with manure water once a week, the amount applied being the same as that given in an ordinary watering with tap water, about "><> c. c. for 193 \l \ \ l l;l . ()3 each t-inch pot. The application was made to -i\ cultures, contain- ing altogether 156 plant-, exactly comparable with a similar number of plant- receiving no manure water. 'The applications wort? made in April and Ma\ and varied in number from five to eight. In all six cultures the plant- to which manure water had been applied made a more vigorous growth, temporarily at least, than those that received none. Similar results were secured by the use of one-tenth cow manure, t're-hh i-otied. in the peat mixture in w hich the plants were potted. It was after the beneficial effecl of this manuring had begun to -how itself that a statement of similar results nearly a century old, in the culture of heath-, came to the writer'- attention. It is con- tained in a hook l>\ William McNab entitled "A Treatise on the Propagation, Cultivation, and General Treatment of ('ape Heaths," published in 1832. The original i- now rare, bul a reprint was pub- lished in 1908 in Note- from the Royal Botanic Garden, Edinburgh, volume ■">. pages 351 to 374. McNab, who was the superintendent of the Edinburgh garden from 1810 to L848, was undoubtedly the most intelligently successful grower of Cape heath- at the period of their greatest popularity. Hi- treatise is original and practical and delightfully written With reference to the manuring of heaths he states : l may mention that l have used a small quantity of manure in the foregoing compost wiih very g l effect, aboul one-eighth pan of cow dung. This should l>e well potted before it is used, 'the way thai I have always prepared this dung before using it is to lake a barrow lead of ii and place il in thin layers between layers of peat earth, and after it lias lain for seme time, chop the whole en together, and turn ii oxer at intervals till the dung disappears and the whole mass assumes the appearance of black peat earth and sand; and where this manure is applied aboul an equal quantity of sand should be added (thai is. aboul one-eighth part >>f the whole) ii. addition to the sand that I have before recommended to he mixed up with the earth. This, I know, can be used with very good effect, but for all ordinary purposes 1 consider it quite unnecessary, as there is no difficulty in growing heaths very soon too large for tlie accommodation that is generally allotted for them, with the compost that I have mentioned without manure. I merely mention this because I know it is the opinion of some that heaths will not thrive wilh manure added to the peat earth in which they are grown. I know, however, ihat some heaths may be grown to a larger size, in the same space of time, witli manure than without it: tint, as I have already mentioned. I consider it quite unnecessary for all ordinary purposes, and any person who wishes to tt\ its effects should do -o very sparingly at lirsl. till he is enabled to judge Of the effecl produced by It, as a little excess of manure is sure In injure the plants. Perhaps liquid manure might be used with very u r 1 effect for growing some kinds of heaths, hut I am unable to give any particular direc- tions in what proportion it should he used. as. from wiiat trials I have made. 1 can not come to any certain conclusion But this much I know, that whoever wishes to try it should do so at titst wiih great caution, witli quite as much as in using an excess of manure in its solid state. 103 64 EXPERIMENTS IN BLUEBERRY CULTURE. McNab's conclusion that manure, while beneficial in small quan- tities, should be used with caution or not at all agrees with the conclusion reached from these blueberry experiments. On page 18 of this paper is described the disastrous results of the heavy manur ing of blueberry plants, and in view of the fact that the blueberry makes satisfactory growth without manure and that we are not sufficiently informed of the exact conditions under which manure may become injurious, the use of even small amounts for blueberries is not now recommended. A suggestion may be made, however, as to a possible reason for the injury of blueberry plants by manure. In the glass-pot experiment described on page 18, in which plants grown in a mixture containing half as much manure as peat made exceptionally good growth at first in it soon died, the death of the plants was preceded by a rotting of the roots. Now, manure is alive with myriads of bacteria, while peat contains few. An examination of the two made by Mr. Karl F. Kel- lerman, from samples taken from the kalmia peat and the cow manure used in these experiments, showed 2,500 bacteria per plate in the Pig. 2G. — Spores of a supposedly injurious fungus in the epidermal cells of blaeberry roots. (Enlarged GOO diameters.) manure and 70 to 150 in the rotted peat, each plate representing 0.0004 of a gram of material. The bacteria in the peat were chiefly of two species, while the manure contained many. It is a reasonable supposition that the rotting of the blueberry roots may have been caused or aided by the bacteria in the manure or by some of the fungi with which manure is also abundantly charged. In mixtures like those recommended by McNab, however, containing much peat and little manure, the injurious bacteria and fungi in the manure may have been killed or held in check by the acids that exist in the peat a in I keep such organisms in control. If experiments show this theory to be correct, the application of manure to blueberries may then be made intelligently. In this connection it may be well to call attention to a peculiar spore found in the roots of feeble blueberry plants grown in unfavorable soils, such as the limed peat and the clayey loam described on pages 23 and 24, and mixtures containing a large proportion of manure. In some of the epidermal cells of the rootlets were found large spherical bodies, as illustrated in figure 26. They usually occurred singly, 193 A. SUPPOSEDLY INJURIOUS FUNG 65 though occasionally two ;in be secured, nevertheless the importance of applying the same practice to larger pots was not rcbal. Km lie. Recherches BioloRiques sur une Chytridinee Parasite «hi l .in. Bulletin de I'Agrieiilture, Brussels, vol. 16, 1900, pp. "ill 554. 5470.S Bull 193 10 66 EXPERIMENTS IN BLUEBERRY CULTURE. appreciated until the best culture from the 11)08 seedlings had re- mained almost stagnant in 4-inch pots for over a month. The con- dition of the plants was first attributed to an excess of acidity in some of the peat used for potting, and next to the necessity of a period of rest from active growth. Neither of these reasons, how- ever, it was ascertained from observation of other cultures, could account except in part for the distressed condition that these plants finally reached. When one of the plants was knocked out of its pot it was in- variably found that a large part of the roots at the side-, of the earth ball were dead. It was at the period of the year. April and May. when the advent of warm sunny days made the control of temperature in the greenhouse somewhat difficult, and this, together with the previous rapid growth of the plants and the consequent increase of their water consumption, had brought about considerable irregularity in the moisture content of the pots. The conclusion was reached that the walls of the pots had become dry on one or more occasions, and that this had killed the delicate roots that came in contact with them. The roots of the blueberry, as described on page 42, are exceedingly slender, the smallest being about two- thousandths of an inch in diameter. They are very quickly killed by drying. On the basis of this conclusion the general practice of plunging blueberry pots was adopted. If the plants are to be exposed to a very warm, dry atmosphere the plunging should be done before any considerable quantity of roots has grown through the soil to the wall of the pot. It is probably still better to do the plunging imme- diately after the potting. Tor then uniform moisture conditions can he secured throughout the soil in the pot. Besides the avoidance of injury to the plants l>y the drying of their root-, the practice of plunging has another marked advantage, the maintenance of a moderate but adequate and even optimum degree of moisture in the soil with infrequent waterings. A series of pots plunged in live sphagnum in a cool greenhouse during the winter of L908-9 frequently went for a week at a time without requiring water and i hen most of the water was applied between instead of in the pots. The moisture evidently moves freely in or out through the wall of the pot. which is of course not glazed, and an excess or deficiency in any one place is soon adjusted. Sand has been found a convenient and satisfactory plunging ma terial. The surface of the sand should come to the same level as the soil in the pot, or a little above it. A little sand on the surface of the -oil does no harm, and indeed is probably advantageous. When a single pot is to he plunged il may he done by placing it within another 193 Ml I huh ' .1 OUTDOOR i I I. I I'KI IN POTS. 67 pol of •_' inches larger diameter, the space between the walls of the two pots being then filled with sand. (See PI. XVIII.) The practice of plunging has proved to lie of (he greatest im- portance in securing ;i large growth in potted blueberry plants, as will lie appreciated from the description of the development made under such conditions out of doors in the summer of 1909. ( See p. 68.) In that description special attention i- drawn to (lie superior conditions of aeration in plunged pots. (27) Plants >>i thi swamp blueberr> sometimes lai down flowering buds \ i i ii i m.i hi seven months. The laying down of flowering buds is discussed in detail on pages 71 to "•">. where a descript ion i- given of the general occurrence of this phenomenon in vigorous plants one year old. The first flowering buds, however, appeared much earlier. They were observed on April 8, 1909, on plants which were in day- less than 7 months old. At the end of the 7 months ■_' I plants out of 258, which constituted seven of the mosl advanced cultures from the seedlings of L908, had laid down flowering buds. A small percentage of the seedlings of 1907 had also laid down flowering buds at about the same age. The phenomenon ma\ therefore he regarded as not rare in vigorous plant- of thi-- age. These flowering buds, which contain the rudiment- of about 7 to 12 flowers each, are not adapted to development into clusters of flowers until they have been subjected to a period id' cold. Most of the buds. therefore, forming just a- warm weather was approaching, withered and dried on the bushes. A few flowered in L908 and in 1909, and in thi- latter year one plant hole ripe fruit on August 25, at the age of a lilt le more than 1 1 months. (28) l\ III! SPRING Mill: llll DANGEB 01 FROS1 WAS PAS! THE PLANTS WERE Kl POTTED AMI PLACED HIT OF DOORS, IN II Ml SHADE, PLUNGED IN SAND. On May 1'.' to 22, L909, the seedlings of 1'.'"- were repotted in 6-inch pots, iii a mixture in mo-t cases of peat 8, -and 1. and loam 1. and placed outdoor-. The plants in the principal culture- had at thi- time' an average height of about !• inches, with a maximum of 15 inches. The pot- were plunged in sand. Thej were in a situation where they were exposed to sunlight from aboul 8 o'clock in the morning to 5 o'clock in the afternoon, and to protecl them from too great heat they were partiaJlj sheltered by a -hit shade. The slat- were •_' inches wide, with 2-inch openings between. A- the sun struck the slats somewhat diagonally and they were half an inch thick, the plants when covered by the -hade- received a little less than half sunlight. On clear day- the -hade- were kept over the plant- from 9 o'clock lo I o'clock. At other hour- and on cloudj days the -hade- were removed. On August •_'."• the time of shading was shortened to the 103 68 EXPERIMENTS IN BLUEBERRY CULTURE. period between in and 3 o'clock, and after September 12 the shades were Left off altogether. The plants were watered with a swift spray from a hose, the water being applied only when necessary to keep the soil from actually drying out. The sand between the pots was seldom allowed to become dry to the depth of more than half an inch. A sand mulch of about a quarter of an inch on the top of the soil in the pot was found useful in preventing the rapid drying of the soil by direct evaporation. 1-1)1 I'.V THE USE OF THE CULTURAL METHODS ALREADY DESCRIBED, SEEDLINGS OE THE SWAMP BLUEBERRY HAVE BEEN CROWN INTO ROBUST PLANTS OF A MAXI- MUM HEIGHT 01 TWENTY-SEVEN INCHES AT TWELVE MONTHS FROM GERMINA- TION. The growth of the plants out of doors during the summer was remarkably vigorous. Hitherto experimenters with seedling blue- berries have been able to produce only comparatively small plants at the end of the first season, as shown by the following citation from a publication of the best -known experimenter:" The blueberry makes much less growth the lirst two years from seed thin the huckleberry, but grows faster afterward. The third year I have had them make a growth of (5 to S inches. The low blueberry and huckleberry begin to bear at •"> or 4 years, while the high-bush blueberry requires 4 to 6 years. From 1 to :! inches growth the first year is about all you can expect. Under the system of treatment described in the present bulletin seedlings have been grown to a height of -~ inches at twelve months from germination. Out of the seedlings of L908, 250 were carried through to the close of the season of L909 in 6-inch pots. Of these. 1.'. were stunted plants. The remaining 235 had an average height at the end of the season of exactly L8 inches. The larger stem- were often a quarter of an inch in thickness, and the main trunk, half sub- merged in the ground, sometimes reached a diameter of half an inch. The general appearance of these plants is shown in Plate VIII. The principal feature- of cultural treatment which have contributed to this development are (a) the autumn germination of the seeds, (b) the use of suitable acid soils, (<-•) the plunging of the pots, and (d) the partial shading of the plant- during the heat of summer, the application of these cultural methods having been guided throughout by the discovery of the existence of a mycorrhizal fungus in these plants and its treatment as essential to their nutrition. The system of germination and the character of the soil- used have already been described in detail. The exact effects of the plunging and the shading remain to be considered. It has already been shown (p. 66) that when a plant is not plunged, (he minute rootlets that lie against the -ides of the pot "Dawson. Jackson. Cultivator and Countrj Gentleman, vol. 50, 1885, p. G60. 193 Bui. 193. Bureau of Plant Industry, U. S. Dept. of Ag Plate VIII. « I nl I'l l;l. IT \ I IN I'l.l" Mil |i I'n I : 69 are very liable to death from dryness. When the pot is plunged in sand and the sand is kept moist these rootlets can not die from drought. They keep on growing until, in the ease of vigorous plain-. when the earth !>al! is knocked from the pot, the soil ran not be seen because of the dense mat of live roots that line the pot. The same thick mass of live roots was developed in a scries of 1907 seedling- carried over the winter of l'- ( tlir moisture conditions, at the wall of the pot very satis fa< tory, for the development of roots there is far greater than within the ball itself. The highlj efficient aeration at the wall of plunged pots may explain one use of soils in which the results of the present investigii lion- do nut agree with the practice of the old heath growers. In one culture of 25 plants tlm soil used in the first potting was pure rotted kalmia peat rubbed through a quarter-inch screen. This firsl potting, in 1-inch pot-, was done on March 20. 1909. The repotting. in 6-inch pots, was (lone on May 22, 1909, in the same kind of soil, pure coarsely sifted kalmia peat. These plants grew to be the largest of any of the seedlings of 1908. their average height at the close of the season being - J0..~. inches. The three plants shown in Plate IX. all over •_' I indie- in height and one of them 27 inches. w ere from t his cult ure. The use of pure peat was not advocated by the old heath growers. McNah recommended a mixture of ! oi 5 part- of peat, by bulk, to I of -and. and an even larger pi'oportion of sand. 2 parts out <>!' •"'. has been recommended b\ Dawson for blueberries. When the pots are not plunged and do not therefore have the advantage of the superb aeration conditions foHnd at the wall of the pol when sur rounded by moist -and. it i> probable thai the presence of consider- able -and in the soil is necessary to secure adequate aeration of the interior of the earth ball, for unless the pot is plunged most of the rootlet- that lie against the sides of the pot will be killed and the plant nin-i rely for it- chief nourishment on the roots in the interior of the ball. That the necessity for interim aeration in the pots is greal in the case of heaths, if the plant- are not plunged or are not frequently repotted, is shown by a peculiar and interesting cultural practice long tried and highly recomniended by McNab. This practice is the distribution of broken crocks or pieces of sandstone through the -oil at the time of repotting. He found by experience thai the prac (ice was highly advantageous t<> the plants, nnd although he did not directly explain his success in such a way, there is little doubt thai 70 EXPERIMENTS IN BLUEBERRY CULTURE. his method, which may be regarded as a substitute for plunging, was advantageous because it gave large aeration surfaces about the stones in the interior of the earth ball and provided a place there for a large development of roots which could not take place at the wall of the pot. McNab's description of his method of repotting is as follows: In shifting heaths I never reduce the old ball of earth more than by rubbing the sides and bottom with the hand, so as to loosen the outside libers a little. I have often shifted heaths twice, and even three times, in the course of the spring and summer, with the greatesl success. It is. however, quite unnecessary to shift a heath until the young fibers have come through the fresh earth given to it at its previous shifting, and begun to extend themselves round the inner edge of the pot or tub: but as soon as this lakes place, they may then lie shifted with advantage. This frequent shifting, however, is quite unnecessary, unless it be to encourage a favorite specimen; for in all ordinary cases, particularly when the plant is large. I consider one good shifting in two or three years quite sufficient. * * * Besides the compost and draining which 1 have already mentioned, when I begin to shift heaths I have always at hand a quantity of coarse, soft free stone, broken into pieces, front an inch to 4 or 5 inches in diameter. Of these I always introduce a quantity among the fresh earth as it is put into the pot or tub. round the old ball of earth about the plant, and press them well down among fresh earth as it is put in. This I consider of great advantage to all sorts of heaths, 1ml more particularly so to those that may have been shifted into a much larger pot or tub at once than what it bad been grown in before, or in what I would call biennial or triennial shifting. These pieces of stone may be put in as large as the opening will admit between the old ball and the edge of the pot. In some of our largest tubs this opening is full 4 inches wide, and where much earth is required to be put in the bottom over the draining before the plant is put in. a quantity of these stones should be mixed with the earth also. I likewise use occasionally large pieces of soft burnt broken pots, put anion:.' the earth in the same way as the stones: but I prefer stones when I can procure them soft and free of iron. The quantity of stones which I introduce along with a large-sized heath at shifting, will, in most cas-s, if broken down into sand, and added to the sand previously in the soil, form about one-third part of the whole mass. When stones are introduced among the earth in the w:i\ I have recommended, heaths will never suffer so much in the summer from occasional oeglect to water them as they would do if the stones were QOt intro duced, because these stones retain the moisture longer than the earth, and in the winter they allow a freer circulation of any superabundant moisture which may be given through the mass. The effect of the half shade used over the blueberries during the summer of L909 was to make (he growth of the plants continuous instead of confining it to a brief period in the early part of the season. In a wild state the twigs of blueberry plants stop growing in early summer, the stoppage being indicated by the withering of the upper most leaf rudiment. The less vigorous twigs stop first, (he more vigorous ones next, and the shoots last. Stoppage of growth is has- tened by hot dry weather and is deferred by cloudy humid weather. In the latitude of Washington stoppage of ordinary twig growth in wild plants of Vactinium of an inch (3.5 to 7 mm.) long, several times larger than the leaf buds. They -how ordinarily in to 1"> external, broad, overlapping scales. Each flowering laid contain- the rudiments of a raceme of usually 7 to L2 flowers, the hud of each in reality situated in the axil of the uppermost leaf, except in the rare cases in which the twig lip doe- not wither when it stops it- growth. In such cases a true ter- minal hud i- formed, surrounded by a group of lateral buds in the axils of bracts. So far a- observed these buds are always flowering hud- and are produced mi the end- of vigorous shoots. The manner in which the plants lay down their flowering buds, through the transformation of leaf hud-, is very interesting, and it im;i\ prove to have a bearing <>i' some importance on the method and time of pruning the bushes. The form of the leaf buds ha- already been described. They appear singly in the axils of the leaves almost 103 7'2 EXPERIMENTS IN BLUEBERRV CULTURE. as soon as the leaf is fully developed. After a few weeks the external scales of the bud turn brown and the bud then goes into a condition of dormancy, unless it is forced into growth through an injury to the twig or some other unusual circumstance. In most of the buds this dormant condition continues through the summer, fall, and winter. If the plant is in condition to lay down flowering buds, however, a new sort of activity appears in the late summer or autumn. One or mote of the leaf buds near the end of a twig start to grow. The two brown scales are spread apart, new green scales appear between them, and a large, bit. flowering bud is formed. The bud does not. how- ever, continue its growth at this time, but its green new scales turn brown and the condition of dormancy is again resumed before cold weather comes on. The flowering buds thus develop out of buds which ari' in no way distinguishable from leaf buds. They are, in fact, leaf buds until their transformation takes place, and except for such transformation they would remain leaf bud-. Furthermore, it has been found ex- perimentally that after the formation of flowering buds has been completed, leaf buds still lower on the twig can be forced by suitable treatment to transform themselves into flowering buds. Such an ex- periment was made, as follows: ( )n August •_'!. 1909, at Lanham, Md., a vigorous bush of Vaccinium atrococcum was selected, which had already laid down it-- flowering buds for the succeeding year. Two branches of nearly equal size, about 1C> inches long, one with 14 twigs and 53 (lowering bud-, the other with 16 twigs and IS flowering buds, were chosen for the ex- periment. On the branch containing the 18 flowering buds each twig was cut oil' at a point between its lowermost flowering bud and its uppermost leaf bud, with the object of ascertaining whether any of I he leaf buds on the stub of the twin' would transform themselves into flowering buds. The other branch was left unpinned as a check. to show whether the normal laving down of flower buds had in reality been completed on August "24. On October 1, 1909, the two twig- were again examined. The pruned branch had laid down :'>1 new flowering buds, which in all cases were the transformed upper leaf buds on the -lulis of the twigs. On the check" branch only 1 new flowering bud had been laid down. The best method of pruning the swamp blueberry is yet to he devised, hut if a superficial pruning, like that of a hedge, prove- to be a good method of stimulating vigorous growth, it is evident from this experiment that the most advantageous time to do the prun- ing, if a crop i- to be secured the next year, is after the berries are gathered and about the time when the bush is forming it- next year's flowering buds. It will then lay down new flowering buds on the cut stubs. If the pinning were done in late autumn, in the winter, 193 Bui. 193. Bureau of Plant Industry. U. S. Dept. of Agriculture. Plate X. \\ I Kl NG Bl l>s FORM |,|, l \ | \ | i Sl'MMI R. 73 or m the spring, no nr« flowering buds would be formed to replace those removed bj i he pruning. The time of laying down flowering buds seems to lie correlated with the length id' die growing season. About Washington V actinium atrococcum begins to form its flowering buds in the latter pari of Au- gust, one to two months after its berries are mat ured. In Vact inium pallidum, on the high mountain summits of North Carolina, where the growing season is short, the transformation of leaf buds into flowering buds begins as early as the la.-i week in July while some of the berries are -till preen. In the cultivated plant- at Washing- ton the formation of flowering buds did not begin in 1909 until Sep- tember, and it continued on some plants until cold weather stopped t heir grow th. The laying down of flowering buds appears to be a phenomenon local within the twig. Cuttings of the swamp blueberry made in New Hampshire on July 9, L909, transformed their leaf buds into flowering buds in the cutting bed after reaching Washington, as shown in Plate X. figure l'. but whether the transformation in this ease was made before or a tier the cutting had rooted was not observed. In another case, however, that of cuttings made in New I lamp-hire September 11. 1909, from long late shoots bearing only leaf hud-. the transformation into flowering buds began to occur in the cutting bed October L2 and was completed before any roots had formed, i PI. X. fig. 3.) l.'ill.Vl III! END OF I Mill: FIRS! YEAR SEVENTH PER 'INI OB I 111 BLUEBERRY PI Wis II \\< 1 \lli DOWN FLOWERING BUDS FOR Till [»EXT SPRING'S BLOSSOMING. At the end of the season of 1909, 177. or 7') per eont. of the 250 seedlings of 1908 that had been put in 6-inch pots had developed flowering buds. In Plate XI i- shown one of these seedlings, pho- tographed on November •_'. 1909, which had laid down 12 flowering hud-. One plant produced "> v flowering hud-. At the end of the preceding season, 1908, al leasl 25 per cent of the seedlings of l'.»07 that were still kept in pots hail produced flowering buds. Therefore, notwithstanding the statements of earlier experimenters that the seedlings of this species not fruit until they are several years old (p. 08). it i- regarded a- established that under the culture system worked out by these experiments a substantial percentage will lay down flowering buds at the end of the first year and will bear fruit the second year. Attention has already I n called (p. 67) to the occasional laying down of flowering buds when the seedlings were only 7 month- old, followed rarel\ l>\ flowering and fruiting at the age of less than i year. 103 74 EXPERIMENTS IN BLUEBERRY CULTURE. (32) Plants of the swamp blueberry are exceedingly hardy and pass the winter in good condition outdoors when the soil is covered merely with an oak-leaf mulch, but when not exposed to outdoor condi- tions they do not begin their growth in spring in a normal ma.w1 b. During- the fall, winter, and early spring of 1908-9 a series of blue- berry seedlings of 1907 was kept outdoors on a south window sill to ascertain whether repeated freezing and thawing would kill them. Most of the plants were in thin glass 3-inch pots, covered at the sides with one thickness of gray blotting paper. One plant (to which reference is again made on pp. 75 and 7G) was in a 5-inch earthen pot. None of the plants were mulched or covered in any way. They were watered whenever necessary to keep the soil from drying. In cold weather the air circulated freely about the pots and the soil was repeatedly frozen solid. On warm, sunny days the melting of the ice look place rapidly. Hard freezing followed by quick thawing was many times repeated, and the conditions of exposure were such that the plants undoubtedly were subjected to a severer test for hardiness than they would ever receive under cultural conditions. The plants passed the winter without losing any of their twigs. The wood was plunrp and in excellent condition when spring came. as was evidenced further by the remarkable uniformity with which every dormant bud started to grow after the first few warm days. For the roots of some of the j^lants in glass pots, however, the exposure was too severe. In some of the glass pots no root growth followed the starting of the twigs, and the plants finally died. In others the root growth at first was feeble and the plants lost some of their newly started twigs by withering. Most of the plants, however, including the one in the 5-inch earthen pot, made normal growth of both twigs and roots, notwithstanding the extraordinarily severe treatment to which they had been subjected. No difficulty is antici- pated, therefore, in wintering blueberry plants successfully out of doors under any ordinary cultural conditions. The seedlings of 1908 covered with oak leaves in their outdoor plunging bed of sand passed the winter of 1909-10 in good conditio]). That blueberry plants must be subjected to some sort of exposure, if they are to start satisfactorily in the spring, is indicated by the behavior of certain seedlings of 1907 which were carried through the winter of 1908-9 in a rose house, where the temperature at night was about G0° F. and during the day about 10 degrees higher. These plants, although subjected to most persistent coaxing, absolutely refused to grow during (he the five months from November to March, although newly germinated seedlings grew luxuriantly under exactly the same conditions. The comparison of these indoor plants with outdoor plants may best be made by an examination of the buds shown in the accompany- 193 Bui. I 93, Bureau of Plant Industry, U. S. Dept. of Agriculture. Plate XI. PLANTS I" BE WINTERED OUTDOORS. 75 ing illustrations, made from typical indoor and outdoor specimens. The photographs reproduced in Plate XII were made on March l'7. L909. The plant shown in figure 1 of this plate was a seedling of September, L907, which had been kept in a greenhouse all it- life at a temperature suited to the growing of roses. The plant shown in Plate XII, figure 2, was identical in history with the other until October 20, L908, when it was placed outdoors and exposed to the severest winter conditions. It was one of the window-sill plants de- scribed on pane 74. The leaves shown on the indoor plant | PI. XII, fig. I) are those formed in the summer of L908, which by reason of the warm temperature of the greenhouse in which the plant was wintered had never fallen off, although the plant had made no growth later than October, L908. Neither a flowering hud nor a leaf hud has started on this plant. On the outdoor plant (PI. XII. fig. 2) the I flowering buds and 62 leaf buds which had lain dormant dur ing the winter had begun to push a few day- before the picture was taken. Plate XIII, from photographs taken on April 24, 1909, -hows the same two plants nearly a month later. The leaf buds on the outdoor plant (PI. XIII. fig. 2) ha\e grown into leafy twigs and the flower- ing buds are fully opened. Of the dormant buds on the indoor plant (PI. XIII. hi:, n only two have -tailed to grow. Of these two new twigs, one on the stem to the left, in the axil of the third leaf from the top. ha- withered it ~ tip and -topped developing before making a full-sized leaf. The other new twig, on the stem to the right, developed abnormally from the axil of a basal bract of a flowering hud. It later made g I growth and became a very vigor- ous -hoot. All the flowering buds on this plant dried up and pro- duced no flowers. The erratic starting of dormant plant- which have not been sub- jected in the conditions necessary to bring them out of their dor- mancy in a normal manner i- well shown also in Plate XIV. This illustration is from a photograph taken February I s . L909. The plant was a seedling of September, L907, which was brought into the greenhouse in early December, l'.K)S. and remained there during the winter. The illustration shows that only one of the two flowering buds on the upper twig has started, one of the four on the lower twig, and none of the lea f hud-. There can be no question thai for ordinary purposes blueberry plant- should be wintered outdoor-. If it is desired in experimental work to force blueberry plants to fruit in a greenhouse during their second winter, it will be necessary cither to etherize them or to find out some other method of treatment by which the starch in their twigs can be transformed into other carbohydrates available for the building up of new plant tissues. The writer believes that in the 193 7(> EXPERIMENTS IX BLUEBERRY CULTURE. hard-wooded deciduous-leaved tree- and shrubs of cold countries this transformation of starch will be found to be caused normally by the changes, probably enzymatic, that follow exposure to an alternation of high and low temperatures rather than exoosure to a single low temperature. (33) DORMANl PLANTS MAKE I 1 1 1 1 1: EARLY SPRING TWIG GROWTH BEFOR] M \v ROO is BEGIN TO DE\ II OP The root growth of blueberry plants in early spring is verv slug- gish, in strong contrast to the activity of their stems. In the plant illustrated in Plate XIII. figure 2, no new root growth had taken place up to the time the photograph was made. For their early spring growth blueberry plant- seem to depend on the food stored in their twigs the year before. A microscopical examination has shown that the pith and medullary rays of winter twigs are gorged with starch. It may he of interest to state here. a- hearing on the difficulty of making stem growth exhibited by an improperly wintered blueberry, that the indoor plant shown in figure 1 of Plates XTI and XIII had made considerable new root growth at the stage shown in Plate XII and abundant root growth in Plate XIII. The starting of dormant buds appears from this and many other similar cases not to be influ- enced by the presence or absence of new root growth. A practical suggestion based on the late spring root development of the blueberry is that transplanting may perhaps he done up to the time of flowering with little injury to the plant. (34) I M.Kss POLLINATED BY \ N OUTSIDE AGENCY, SUCH \s I\sii I >. Mil FLOWERS PRODUCE LITTLE OK NO FRUIT. Many blueberry plants, from seed germinated in September. L907. were brought into flower in one of the Department greenhouses dur- ing the winter of L908 '•». When left to themselves the flowers rarely produced fruit. The greenhouse contained few pollen-carrying in- sects, a few ants and tlies merely, no bees. It was found that the flowers were so constructed as to he unable ordinarily to pollinate themselves. The lack of fruit was evidently due to lack of pollina tion. When pollinated artificially the flowers usually produced fruit. In its natural position the flower (fig. 27) is not erect hut in- verted, the narrow orifice of the corolla being lowermost, the nectar welling up from the surface of the disk between the base of tin style ami the base of the filaments. The ten stamens and the style hang downward within the corolla, the stp.mens being shorter than the style. The pollen when mature drops down from the two anther sacs through the two anther tubes which the stamens of these plants possess and out at the terminal pores. 'See fig. 28.) 193 13, Bureau of Plant Industry, U S Dept. of Agi Plate XII. - x r Ml i 5i M O T- O 3! Bui. 193, Bureau of Plant Industry, U. S. Dup: Plate XIII. ? CD > H I o Z I H « I > (71 CO CDS P — Z H 2. £ CD O POLLINATION OF THE BLUEBEKRN FLOWER. 77 Fig. 27. Flowers of tin' blueberry, from 1908 s I lin^s of the lai ed Nen Hampshire bush of I lit- between the anther uiIm's. The anther tubes are stiff and when one of them is pushed to one side the movement is communicated to the an- ther sac. The pollen if mature is dislodged and falls dow n the tube and out ;tt the orifice. The pollen does not eonie nut of the anthers readily on a cloudy, humid day. but on a warm, sunny, 'Ivy day it accumulates in the tubes and when they are moved it run- out like grain from a grain chute. The pollen grains (fig. 29) do not stick to the sides of the parchment-like anther tube- when these are dry, but they have the faculty of adhering to hard surfaces, such as glass or the lend of a lead pencil, and they doubtless would adhere also to the hard -hell of an insect whether it was covered with hair- or not , The pores of the anther tubes do not open squarely across the ends id' the tul»e-. but they are set on a long bevel facing inward. The pollen when released would there- fore fall upon the stigma were it not for a peculiarity in the -true- lure of that organ. The sticky stigmatic surface, which the pollen inu-t reach to effect pollination, is at the apex of the globular or top-shaped stignia, while the sides of the stigma a- far up a- the middle have a '\vy surface ending in a -hoit collar a little wider, during the curly maturity of the stigma, than (he widest part of the stigmatic surface. (See fig. 30.) In the inverted position of the (lower the falling pollen strikes tin- dry 193 Fig. 28. Stamens of 1 1 1 . - blueberry, from Bower shown in flg. 27, <■ : //. View from the Inner I side view. Both views show the broad filament wiili hairj margins and the anther i ubes, and pores. i Enlarged ." diameters, i 78 EXPERIMENTS IN BLUEBERRY CULTURE. Fig. 29. — Compound pollen grain of the blueberry, consisting of four simple grains permanently cohering. (En- larged 200 diameters, i surface, like the outside of an inverted funnel, and drops off the rim or remains on it, without reaching the stigmatic surface which lies protected beneath. Ordinarily pollination is effected by some insect which, pushing into the orifice of the corolla from beneath in search of nectar, releases the pollen, as already described. In continuing its quest for nectar the insect brushes against the stigma with some portion of its body. which is covered with pollen, either from the same flower or from some other flower previously visited. In pollinating the flowers by hand it was found impracticable to collect sufficient pollen to apply with a brush. The following sim- ple and convenient method of pol- lination was devised: A wide opening was torn in a corolla with a pair of forceps, so that the stamens and stigma could be approached from the side. Then the lead of a lead pencil, flattened on one side and held horizontally, was brought up against the open end- of the anther tubes from below. A portion of the falling pollen was caught en the flat lead, where it could be seen easily because of the blackness of the background. Pollination was then completed by touching the stigmatic surface gently two or three times with the pollen-laden lead. A pollinated flower may be marked readily by pinching off with forceps one or more of the calyx lobes. Fruit was produced from flowers pollinated either with their own pollen or with pollen from another flower. The self-pollination of a blue- berry flower, without insect aid. ap- pears to occur, but only occasion- ally. On greenhouse plants fruit fig is rarely produced when the (lowers are not artificially pollinated, and the same is true of outdoor plants protected from insects by a covering of gauze. The conditions of these observations were not such as to obviate all possibility of the accidental visit of some insect, but it is believed that real self-pollination occurred in some cases. (35) 'I'm: FRUIT MATURES ABOUT TWO months Mill: MM FLOWERING. A few days after pollination the corolla, with the stamens, falls off. The stigma al this time has turned brown, and within a day or u»:: .30. — IMstil and calyx of (lie blue- berry, showing the style and stigma. (Enlarged ."> diameters.) Bui. 193, Bureau of Plant Industry, U. S. Dcpt. of Agriculture. Plate XIV. a S a c ; > a 3) "" o If 3- 5. m 9 D 2 » 8 ■« TJ ■"■• r ~ > S z B O £ 8 RIPENING OF THE I'IM'IT. 79 two the style also falls. The calyx remains permanently attached to the ovary and berry. About a week after the opening of tin- corolla, the "\ ary, which at first was much narrower than the expanded calyx, begins to swell and grow. This growth continues for about a month, and then for about another month (lie green berry make- little in crease in size. A few day- before the time of ripening the calyx turns purplish, nexl the green color of the berry lake- on a trans- lucent appearance, the next day it turns to a light purple, and the following day to a dark purple or whatever it- permanent color may be. During these leu day- die berry make- a very rapid growth, its diameter often increasing 50 percent. After reaching it- permanent color the berry changes little in size, but for several days continues to improve in sweetness and flavor. It i- a characteristic of blueberries, important from the standpoint of picking, thai after ripening they will remain on the hush a lon« time, often a month or more, without losing their plumpness or their flavor. This make- possible the removal of all the berries fit 111 i bush at one clean picking, unless to catch a fancy market a partial early picking i- desired. It i- of intere-i to record that although the largest berry observed on the parent bush of the seedlings of September, 1907, was 0.46 of an inch in diameter, a berry ripened in the greenhouse on one of these seedlings measured on April 2-1, 1909 (PI. XV), 0.49 of an inch in diameter, and August 2, 1909, one of the same seedlings had a ripe berry <»..", of an inch in diameter. (36) So FAR \- OBSERVED THE SWAMP BLUEBERRY WHEN GROWN IN vein soils Is I I I 1 I I SUBJECT TO FUNGOUS DISEASES OR INSEC1 PESTS. Like all plants grown in greenhouses, blueberry seedlings need to he watched in order to detect and -top promptly any fungous or insect pest- that may appear. With the exception of the Asterocystis-like root fungus described on pane 65 a- occurring on sickly plant- in alkaline soil-, the only parasitic fungus found on anv of the plant- was a mildew identified by Mrs. flora \Y. Patterson a- Microsj)haera alni vaccina, which ap- peared sparingly when the atmosphere of the greenhouse was too moist. This mildew is abundant on Vaccinium racillans, hoth wild and cultivated, hut the swamp blueberry i- very little subject to it- attack-, an important characteristic. This fungus would doubtless respond readily to the ordinary treatment for mildew with pulverized sulphur. Amon- insects a green aphis sometimes threatened to damage the growing twigs, but it was easily destroyed by tobacco fumigation. The greenhouse red spider {Tetranychus himaealatvs) infested some of the cultures, e-pecially in the warmer greenhouses, occurring chiefly on the hack- of the leaves, an. I seriously injured the plants 193 80 EXPERIMENTS IN BLUEBERRY CULTURE. unless promptly checked. The mosl satisfactory treatment was to syringe the plants once or more a day with ;i swift spray of water, repeating the treatment until the animals were cleared off. A pathological condition observed in the summers of both 1908 and 1909, at first supposed to be physiological in cause, has now been traced to an insect. The young leaves of tender shoots become .semi- transparent or "watery" in appearance, remain small, develop a faintly rusty color on the lower surface, tend to become slightly cockled, and sometimes turn brown and wither. It was finally ob- served that these leaves were infested with a very minute animal, much smaller than a red spider and when not in motion difficult to distinguish with a strong hand lens. Specimens submitted to Mr. Nathan Banks, of the Bureau of Entomology, were identified by him as a mite of the genus Tarsonemus and belonging probably to an undescribed species. A similar and perhaps identical mite had done considerable dam- age to young seedlings in the greenhouse during the winter of 1908-9, its presence being indicated by the conspicuous cockling of the leaves. The difficulty had then been met by the pruning of the affected twigs. It was observed, however, in the summer of 1909 that the mite producing the watery appearance of the leaves did not occur on outdoor plants fully exposed to rain and dew. hut only on plants partly or wholly protected by glass. It is suggested, therefore, that frequent syringing with water may he the proper mean- to control this mite. On the whole, this species of blueberry when properly grown may be regarded as unusually free from the depredations of fungi and insects. IMPROVEMENT AND PROPAGATION. 7) The parent plant of the swamp blueberry seedlings, the culture of WHICH II \s been described, bore berries over half an INCH IN DIAMETEIi. The parent of the blueberry seedlings of 1908 was a hush of Vaccinium corymbosum selected at Greenfield, N. H., in July. 1908, after three summers of cursory observation in the 1 mountains of southern New Hampshire and three weeks of diligent search in the summer of 1908. The hush grew at an elevation of '.».■"><) feet above the sea. It stood with many other blueberry bushes in an old, brushy, mountain pasture, in permanently moist hut not swampy soil. It was about 7 feel in height, and the largest of the several stems was about 2 inches in diameter. The plant was old and sonic what decrepit, the tops on some of the stems being partially dead. Some parts of the bush, however, were in full vigor, with robusl foliage and twi^s. The leaves were dark green above and pale glaucous green beneath, with entire margins, and smooth on both Bides except for a slight pubescence on the midrib and principal 103 Bui. 193, Bureau o' i . U S Depr Plate XV. Berry Ripened on a Blueberry Seedling at the Age of Nineteen Months. A I. \i:i.i BERRIED BUSH. 81 veins of the upper surface. They were of large size, on the fruiting twigs reaching ;i length of 2 inches and ;i breadth of 1 inch and on vigorous shoots having the corresponding measurements ■_'.."> and 1.5 inches. The character of the leaves is mentioned in detail because of the remarkable variation shown in the leaves of the seedlings, particularly in size, toothing, color, and pubescence. The large flowers produced in the spring of L909 were 0.4 of an inch (10 nun.) long from the base of the ovary to the tip of the corolla; the sepals were very short, and the corolla white and nearly cylindrical. The berries were of large size, reaching a diameter of over half an inch. The color was an unusually pale blue, due to a dense bloom or glaucousness over the nearly black surface. In form the berrj Wits nol spherical, but somewhat depressed or tomato shaped. The calyx in the ripe berry (Pi. VI, fig. L) was almost obliterated, because it was small in the beginning and because of lateral stretch- ing of the berry in acquiring its depressed form. This smallness of cal\ \ is of importance, because in such a berry no shelter is afforded beneath the sepals for insects, and also because the amount of " rag," or indigestible skin, is much less than in a berry with a large calyx. In Savor the berry was exceptionally good. It was sufficiently acid to be decidedly superior to the mild, sweel berry of Vaecinium pt nn- sylvani&um, ye1 nol sour like the berry of V. canadense. It repre- sent- one of the best types of flavor in the variable V. corymbosum. The only unfavorable feature of this bush was the lateness in the maturity of it> berries, a characteristic of the species to which it belongs. The earliest New England berries, which bring the fancy whole-ale price of •_'() cent- or more per quart for the first few days, as described on page L2, are those of the dwarf Vacciniufn penn- sijl I'unh nm. which mature about two week- earlier than those id' 1'. cori/mhiisuii). The size of the berry is of such importance as to warrant an exact re "id of the measurement, not only of the largest berries bul of all the berries from an average picking. On A.ugus1 ■_'. L908, an average pint of berries was taken out id' a clean picking of this bush and each heri'v was measured. The measuring was done by means of a metal plate containing a -eric- of circular hole- 5, 6, 7 mm., etc.. in diam- eter. The pint of berries showed the following sizes: l»inni«'(rr of berry. Number of berries. 7 to s mm 2 8 I- 9 mm 50 9 I" L0 Him 1!il 1 11 in in 278 11 to 12 mm i:;7 1- t" t:'. inm . 10 13 I" 1 I mm U71 .MTiis Bull, fa:: H» 6 82 EXPERIMENTS IN BLUEBERRY CULTURE. The largest berry measured on this bush was 14.02 mm. (0.552 of an inch) in diameter. Three quarts of berries were picked from the bush; all those less than 10 mm. in diameter were discarded, and the remainder, about 2 quarts, were carried to "Washington for seed purposes. (38) There is every reason to believe that thk blueberry can be improved by breeding and by selection. The swamp blueberry (Vaccinium corymbosum) is an exceedingly variable bush. There are three especially well-marked forms, called T. amoenum, V. atrococcum, and I*. pallidum, by some authors regarded as distinct species, by others as forms of I'. corymbosum. Within the limits of these forms variation is also extensive. There i^ great opportunity for selection among wild varieties in the size, color, flavor, and time of ripening of the berries and in the productiveness and vigor of the bushes. That types possessing desirable qualities can be crossed there is no question. A method of pollination has already been described (see p. 78), which, supplemented by the removal of the stamens on the female parent before they have matured their pollen and also by the protection of the pollinated flowers from insects, would insure a genuine cross. The possibility of securing valuable varieties is accentuated by the marked variation observed in the character of the offspring of the large-berried bush from which the seedlings of 1908 were grown. Be- sides minor variations, these seedlings show three forms which may be regarded as types. One of these, characterized by its low stature and leaves tending to be conduplicate and by it- long persistence into the winter in a green state, is perhaps the result of some pathological difficulty. Two of the types, however, appear in every way to be normal. One has its leaves huge, obovate-elliptical, glaucous on the back, and with entire margins, such as are possessed by the parent, and are typical of true Vaccinium corymbosum, and it develops only a few though very robust steins, with few flowering buds. The other has smaller, narrower leaves, green on both surfaces, and with mar- gins closely and evenly serrulate. It produces many stems smaller than those of the other, and more numerous flowering buds. It is strongly suggestive of the plant called Vaccinium < num. It is much larger and more robust than I'. pennsylvanicum, and may pos- sibly be a hybrid between that species and I'. corymbosum,. The characters of bush and foliage in these two types have not yet been correlated with any differences they may show in (lower and fruit. It is, however, of great interest that these same two types occur among the seedlings of 1907, as well a- those of L908, which '.line from a different though similar bush growing about 2 miles IV the other. L93 Ml rHODS OF PROPAGATION. 83 (39) 'Till SWAMP BL1 S PROPAGATED in GRAFTING, B1 BUDDING, BY I \\ I IMNc. B1 rWIG il [TINGS, \\l> BY BOOT M [TINGS. On March 2, 1909, a few scions of the large berried bush from NVu Hampshire, dormanl winter twigs, were grafted on seedlings of L907 which had been started into growth in the greenhouse. The actual work of grafting was done by Mr. Edward Goucher. All were simple splice grafts, the diagonal cut being about 0.75 of an inch in length, the diameter of stock and scion at the point of contact about 0.15 of an inch, and the length <>f the scion about 2.5 inches after it was cul off at the tip just below the lowest flowering bud. The splice was wrapped tightly and completely with raffia, but no wax was applied except to the cul tip of the scion. In order t<> prevent a pos- sible injurious degree of evaporation from the scion, the whole graft, which was near the base of the plant, was surrounded nearly to the tip of the scion with a loose mass of sphagnum, which was kept slightly moist though well aerated. A.11 the scions put out new growth from their buds in about ten days. In hall' the grafts union did not take place, the new growth finally collapsed, and the scion died. In the others the surfaces united satisfactorily and the wrapping was removed. By the end of the season of 1909 the grafts had made a growth of •"> to 8 inches and had laid down flowering buds. (See PI. XVI, 6g. 1.) The first experiments in budding were begun on August 13, L909, tin- work being done by Mr. Henry II. Boyle. Seven seedlings of L906 and 1907 were budded with summer leaf buds of the large- berried Vaccinium corymbosum bush from New Hampshire. On A.ugust 16, 6 other seedlings of L906 and L907 were budded with buds from large-berried plants of V. pallidum from North Carolina. On September ■_' and :'>. 1909, 26 more seedlings, of 1907 and 1908, were budded with hud- from the New Hampshire hush. The buds were inserted near the base of the plan! on stems 0.25 to 0.5 of an inch in diameter. The method of procedure was that used in ordinary hud ding, as of peaches, the same T-shaped cut being made in the hark of the -lock, the hud wood cut to the length of half an inch or a little more, and the bud after insertion wrapped tightly with raffia. The percentage of success in the budding was small. Out of the 39 plant- budded only L6 retained their hud alive and in apparently good condition at the end of the season, and the following spring only 5 were alive and in condition to grow. Plate XVI, figure 2, is a reproduction of a photograph of one of the successful buds from the large berried New Hampshire bush, taken in the winter of L909 L0 after union had taken place, the wrapping had heeii removed, and the stock hail heen cut nil ;iImi\ e the hud. iments on some of the feature- of these budding experiments may he useful i" other experimenters. Tie- growth of the stems I'..:; S4 EXPERIMENTS IX BLUEBERRY CULTURE. during the portion of the season remaining after the budding was sufficient to strain the wrappings and, unless the bud wood was held tightly for its whole length, to push the hud out of place. It was found best to leave the bud tightly wrapped to the end of the season, notwithstanding the fact that the stock might become deeply creased and choked. An examination of the buds that failed showed that in mosl cases baik or callus from the stock had intruded between the stock wood and the bud wood, sometimes covering the entire surface. While the bud wood in some such cases was in part still alive and green, it was of course doomed. As late as August 30 in New Hampshire, and September 3 in Massachusetts, bushes of the swamp blueberry were found in which the baik would peel and buds could be inserted. On September 2 no wild bushes of Vaccinium atrococcum could be found at Washington in condition to bud. Even in Massachusetts and New Hampshire, on the dates mentioned, most of the bark on all the bushes and all of it on many bushes would not peel. Bark still in good condition oc- curred mostly on vigorous shoots of the season and in some cases of the preceding season. Sometimes the bark on the north side of an erect shoot would peel when that on the south side would not. Bark still green and whole would peel when near-by bark which from age and exposure had begun to turn brown and split on the surface would not peel. Propagation by layering was carried on in 1908 and L909. In the greenhouse experiments moist live sphagnum proved to be a more successful material than peat and sand in which to root a layered branch. When the branch laid down was one which was hardening its wood but still bearing leaves, it callused and rooted readily in the sphagnum at the point where the bark was sliced, but when a young soft-wooded branch was used it usually began to decay at the cut and finally died. Although several times tried it was never found practicable to sever a layered and rooted branch from the parent plant successfully except at the period of winter dormancy after the leaves had been shed. (40) Tin: Mosl DESIRABLE METHOD OF PROPAGATING THE SWAMP ni.rEBERHY IS BY t UTTINGS. While the surest method of propagating a selected blueberry bush is by layering, and the most rapid method of securing fruiting plants from it is by grafting, both these methods have certain objections which do not apply to the method of propagation by cuttings. Propagation by grafting is objectionable because of the habit the blueberry plant has of continually sending up new -hoot- to replace (he old stems. These shoots come from the root or from the base, of 193 Bui. 193, Bureau of Plant Industry, U. S. Dept. of Agriculture. Plate XVI Fig. 1. -Grafted Blueberry. Fig. 2.— Blueberry Seedling Successfully Budded. The line of union between the .stock and the scion in figure 1 is clearly shown. Two twigs had grown from the scion, a short one near the tip and a vigorous one from the lower part. In ligure shown an inserted i>u<1 which has united y with the stock, bu I has not yel begun to grow. The insel atural size. The two va arc natural PROPAG \ I i"N \:\ CI CTING the stem jusl below the surface of the ground. Originating below the graft they would not bear fruit of the variety desired, and such a grafted plant would always be liable to serious depreciation in value. It is suggested, however, for the benefit of any who may de-ire to follow up this method of propagation, that a plant produced l>\ root grafting would be somewhal less liable than a stem graft to i he product ion of -hoot- from the stock. Propagation by layering i- not open to the objection just raised against propagation by grafting. The difficulty with layering is that only a few plant- can be propagated from a parent in l\\\> way at one time. The method of layering i- slow and therefore, from a commercial point of view . faulty. Propagat ion by cuttings, whether of the root or the stem, is subject in neither of the objections raised to grafting and to layering. In a plant raised from a cutting the whole plant body, including the root, is of the variety desired, and alien -hoot- can never be pro- duced. Furthermore, hundreds or even thousands of cuttings may be taken at one time from a valuable plant and a large stock of off- spring .-an -nun be accumulated. The present objection to the propagation of the swamp blueberry by cuttings i- the difficulty of making a high percentage of the cut- tings "Tow. In this respect the experience of the last two year- may he characterized a- a series of frequent alternations of high hopes and disappointing failure-. The intimate knowledge, however, acquired from these experiment- regarding the behavior of cuttings under many different condition- gives ground for confidence in ultimate success; hut a- we are only in the middle of things in this matter a full description of the experiments with cuttings must be deferred until satisfactory results shall confirm our confidence in the methods used. For the present it may suffice to show an illustration of a plant from a root cutting (fig. 31) and another of plant- from twig cuttings ( PI. XVI 1 | of the big berried bush from Greenfield, N. II. In Plate Will i- illustrated, from a photograph taken in the winter of L909 10, a plant grown from a cutting taken on October L5, 1908, from a line' of September. 1907. Although itself only a year old, and even then taken from a seedling only a year old. the plant after passing the winter of 1908 '- 1 in the greenhouse and the summer of L909 out door-, had laid down 156 flowering hud- at the time it wa- photo- graphed. While these cases -how that swamp blueberry plant- can he pro- duced successfully from root cuttings and stem cuttings, the suce have been so erratically distributed that the recommendation of any particular method i- hardly warranted at the present time. 86 l Al'l i;i.\i KX'is in BLUEBERRY CULI i ! ; I . . It should be stated here that those species of blueberry which spread by rootstocks, such as V actinium pennsylvanicum, and other related plants having the same habit, like the deerberry (Polycodium stamineum) and the dwarf huckleberry (Gaylussacia dumosa), have Fig. 31. — Blueberry plan! grown from :i rool cutting. (Natural size.) been reproduced without difficulty by rootstock cuttings. This method is not generally applicable to the swamp blueberry, however, as large plants of (his species seldom produce rootstocks. FIELD CULTURE. i II i Experiments ii we keen begun in the field culture of thi sw smc blue- berry. While the results of the pot culture experiments arc regarded as highly successful and satisfactory, the experimental field plant- ings made in 1908 and 1909 can not be said to have given more than 193 Bui. 193. Bu'. . U. S Dept Plate XVII. FIELD PLANTINGS. 8*3 promising results. Ii is true that out of one planting of L79 seed- lings of l!K)7 made in ;i partially moist natural meadow at Green- Geld, N. II.. in early July, L908, 97 per cent outlived the severe drought of that summer and the rigors of the following winter, ami 6 percent flowered and set fruit. The plant- were not observed during the ripening season. While this record of flowering and fruiting in plant- 2 year- of age may be regarded as satisfactory in comparison with the several year- supposed by the earlier experi- menters to be required before fruiting, it nevertheless can not be regarded as satisfactory in comparison with the pot cultures from the seedlings of l'.'i> s . of which, as stated on page 73, To per cent were prepared to flower in 1910, their second year. While the results of the field experiment- thus far made are re garded as in no wise approaching what may confidently and reason- ably be expected, they nevertheless may serve even at this early stage to eon\ ey some useful lessons. The held planting of L79 plant- already referred to contained s l plants which had never been potted but were torn apart out of their original seed flat while in full growth and set outdoors in the place indicated. These plant- after such severe treatment never grew to be robusl and none of them flowered. It was among them that all but two of the deaths in the field occurred. That any of the plant- should survive such rough usage is of interesl experi- mentally, but in actual practice such a method should never of course be followed. Most of the field plantings were made in area- where the natural soil hail been chopped with a mattock to the diameter of about 18 inches and the depth of about 8 inches immediately before the plant- ing. Ii i- evident from the comparison of certain plantings made in L909 thai a growing plant when set out in such freshly chopped soil receives a serious setback. On dune I. 1909, 216 seedlings of I'.'iis were set out in new hole- prepared as described above, and is other seedlings of puis were used at the same time to replace dead or feeble plant- set out in the preceding year. These I s plant- there- loir went into soil thai had rotted for a year, although it was in part penetrated again by new roots from the surrounding native vegetation. When nexl examined, on dune 30, the two groups of plant- showed the mosl marked difference in growth. The plants in the new hole- showed the same purpling of the leaves and cessa- tion of growth as did plant- in the greenhouse when suffering from excessive acidity due to potting in raw peat. (See p. 60.) The plant- in the old hole-, on the contrary, were nearly all of g 1 color and growing well. It i- inferred from this observation that blue- berry plants will do better if the holes in which they are -et are 193 88 EXPERIMENTS IN BLUEBERRY CULTURE. filled with peat or peat mixture the acidity of which has been tempered by several months of decomposition. In all the field plantings thus far made the plants were set out while in full growth. Although most of them were in pots when transplanted, and therefore carried their entire root system with them, nevertheless it is regarded as highly probable that a better plan would be to set the plants out when dormant, in the early spring of their second year. Such a plan would offer several advantages which it is hardly necessary to recount. For several days after transplanting, the plants were partially shaded. Paper and the branches of various trees and bushes were tried for this purpose. Pine branches stuck in the ground on the south side of the plants were found by far the best of the shades used. The soil about the plants was mulched in most cases with dead leaves, held in place when necessary by a little earth thrown over them. CONCLUSION. In conclusion, to those desiring to experiment with the field culture of the swamp blueberry, whether with wild plants, seedlings, or plants grown from cuttings, two modes of treatment are suggested. both deduced from the experiments already made. The first method, suited to upland soils, is to set the plants in trenches or separate holes in well-rotted peat at least a foot in depth, and mulch the sur- face well either with leaves or with clean sand. The excavations should provide ample space for new" growth of the roots, not less than a foot each way from the surface of the old root ball. The peat used may be of either the bog or upland type, as described OB pages 32 to 35 of this publication, and should have been rotted for several months before using. The soil in which the holes or trenches are situated should be such as to provide good drainage, the ideal condi- tion of the peat about the roots of the plant being one of continued moisture during the growing season, but with all the five water drain- ing away readily so that thorough aeration of the mass of peal i- assured. If the surrounding soil is sufficiently porous to insure the maintenance of such a moist and aerated condition, without the neces- sity of mixing sand with the peat, better growth, it is believed, will be secured than when such a mixture is used. The second method of field culture suggested is to set out the plants in a peat bog after the bog has been drained, turfed, and deeply mulched with sand. The treatment proposed is the same as that employed in cranberry culture, except that no special provision need be made for rapid Hooding of the bog for winter. The ground water in the bog may probably he kept with advantage a little lower than is usual with cranberries. This method of culture is suggested not 193 Bui. I9 : Plate XVIII. _ -o % i Al'Vh r. CO BXPERIM I \ I ERS. 89 only because of the close botanical relationship of the swamp blue- berry and the cranberry and the known similarity of their ph} r siolog- ical requirements in the matter of peal and moisture, as well as the presence of a mycorrhizal fungus in the roots of both, but also and especially because the mosi robust growth in all the pot experiments occurred when the roots of the plant were feeding on pure peat and the pots were surrounded by moisl -and. The important effects of these conditions arc discussed on pages 68 to 71. Essenl ially the same effects, it is believed, are secured bj the system of culture used for the cranberry. Tin- publication closes with no special summary of results. The numbered statements which form ii- framework arc in themselves a sufficient summary for the general reader, and one who i- led by these experiments to undertake the culture of the blueberry will find it profitable not to begin hi- work until he ha- read the whole of the publication. These plants differ in their -oil requirements so funda- mentally from all our common cultivated crop- that it i- useless to expect to succeed with their culture without a thorough understand- ing id' the principles governing their growth. Those desiring to look into the work of earlier experimenters can find a key to the literature in F. W. Card"- book entitled u Bush Fruits," or in the article by W. M. Munson on Vaccinium, in Bailey's Cyclopedia of American Horticulture. 1 NDE X. i itric, norma] solution, relation to pure lemon juice 28 nutrient solution. See Solution, nutrient il, arid. Acidit) . phenolphthalein test 26 28 , peat, i . etc 22, 35, 'il 62 Aeration, conditions satisfactory for blueberry 17,3" 39,55 necessity in interior of pots 69 promoted l>y plunging potted plants (i.">-(i7, <; n \ ricultural experiment stations. Sei Stations, agricultural experiment. A labama, absence of blueberry and related plants in " black belt" 19 Alfalfa, |>"t cul lures in garden soil and in peat, comparison 15 17 preference for alkaline soils 29 darkening of glass p sarj to prevent growth I"> Alkali, determination by phenolphthalein test 22, 26 28 Alkaline nutrient solution. Sei Solution, nutrient. -oil Si i Soil, alkaline Alpine blui bi n . Sei Blueberrj . alpine. Ammonia of kaltnia peat for growing :ii> Azotobacter chroococcum, nitrogen-fixing bacterium in soil 49 Bacteria, in clover toots, fixation of atmospheric nitrogen 48 19 kaltnia peat and cow manure, comparison I 14 nitrifying, inability to thrive in acid soil 46,47 of ordinary leaf decay, conditions of inability to thrive 31 32 Hanks, Nathan, identification of mite 80 Hark, condition for budding 84 Branch s, basal. slio - Shoots, basal " Belt, black," Alabama, absence of blueberry and related plants pi Berry, size, flavor, etc., in various species 12 importance as market feature 12, II on parent plan! 81,82 I i uit. Belt, black." Blackening, leaves a pathological disturbance Bladderwot ipply of nitrogen o Bloodroot, sod not suitable for blueberry 24 Blueberries, prices in market . .'. 12. si il preferences pt and hucklebi of distil related plants, occurrem e, adherence to ai id soils Sei Bo I'll.- berry. branching types, description mse caustic effect of lime on plants cockling of leaves due to a mite elusions, Bummary, statement. ■ dons, dest ription and development of branches from axih 193 91 92 EXPEBIMENTS IN BLUEBERRY CULTURE. Page. Blueberry, cultivation, possibility, erroneous popular idea 11 cultural features contributing to rapid growth 68-71 flowers, description 76-78 growth, peculiarities 14-50 improvement and propagation 80-86 insect pests 79-80 market price and requirements 12, 81 name usually restricted to plants of the genus Vaccinium 13 nutrition, peculiarities 40-50 peculiarities of growth 14-50 nutrition 40-50 picking methods 13 possible hybrid 82 pot culture, methods 51-80 roots, epidermal cells 42-44 soil deleterious to roses and alfalfa 15-17 requirements 14-40 subalpine, soil preferences 19 swamp, or high bush 11. 14 theory of nutrition 50 variability 82 See also Berry, Fruit, Fruiting, and Market. Bog, blueberry, water level 36, 38-39 cranberry, near Wareham, Mass., growth of blueberry 36 leatherleaf, typical, growth of blueberry in drained areas 35 peat, formation, causes of acidity 31-32 suitability for growing blueberries 88-89 plants. See Plants, bog. sphagnum, growth of cushions 39 water. Sn Water, bog. and Water, peat. Boston, price of blueberries in market 12,, 8] Boyle, H. H., budding of swamp blueberry 83 Bract, formation prior to termination of stem growth 58 Branches, basal, commencement, location and importance 57-58 pine, use as shade for blueberry plants 88 Branching types of blueberry. See Blueberry, branching types Breazeale, J. F., assistance in experiments 27, 32 Breeding, use in improvement of blueberries 82 Briggs, L. J., test of kalmia peat 38 Britton, Mrs. N. L., identification of moss on leaf mold 30 Brown, G. H., on plants in Smithsonian grounds 11 Budding, method of propagation of swamp blueberry 83-84 9. Buds, changing by pruning, experiment vz flowering, method of production 67, 71-73 leaf, tr.in form ition into flowering buds 71-73 Calcareous soil. See Soil, calcareous. < 'aleiuni bumate, occurrence in soils 46-47 oxid in leaf mold, amount 30 Calyx, coloration before ripening of berry 79 relation to quality of berry 81 Canada, relation of blueberries to calcareous soils 19 ( 'ape heaths. See Heaths. t iarbonate, lime, use in pot cultures of blueberry ( aid, I''. \\\, on blueberry cultivation 89 Cells, epidermal, of blueberry rootlets, microscopic study 42 Cellular matter. See Matter, cellular and organic. Centrifugal method. See Soil, moisture measurement. Chamacdaphne calyculata, bog. growth of blueberry 35 Chlorophyll, presence essential to development of carbohydrates 48 < litric acid. Se< \ Dawson, Jackson, on growth of blueberry LI, 68 69 Dei i berrj . propagation by rootstock cuttings undergrow th on noncalcareous soils, Alabama 19 Dormunt plants. Set Plants, dormant. Douglass, John, partial planting of Smithsonian grounds II Downing, A .1 . plan oi Smithsonian grounds 11 Drainage, necessity in field culture 88 I'll - pots 14 See also Watering. ra, insect t 1 for supplj of nitrogen 50 Dry ne.-~, importance as market feature 12 physiological, discussion 3."> soil, injur} to blueberry plants (ii>. 69 Earthwi inns, injurious effects on bin. 'berry plants 38 I i itrophic mycorrhiza. Set Mycorrhiza. Embryo, blueberry seed, development 53 Endosperm, blueberry seed 53 Endotrophic mycorrhiza S Mycorrhiza. matic transformation. v Staj h, transformation. Epidermal cells. Si i Blueberrj , i ea repens, avoidance of limestone soils 1!> Erica spp., i us, study 49 l leaths and Heal her, Experiment station : ! itions, agricultural experiment. Extraction, method i'< r soil-acidity tests '_'7 Farklebernes, undergrowth on noncalcai ils, Alabama L9 ild, M I , ' n d preferences of alpine and subalpine plants in Ferns, use "t" Man land peat for growing 32 Field culture. Set Culture, field. for seedlings Flavor, excellence in parent plant si importance as market feature 12, 81 Flax, injurious fungus in root 65 Fl ling of blueberries in winter Flowering bud- Set Buds. edlings Flowers, description 7> Formulas, acid and alkaline nutrient solutions Frank, A I! , naming of fungus endotrophic mycorrhiza 43 Freestone, pieces, use in soil for repotting heath plants 7<> Freezii on blueben plants Fruit, on a plant eleven months old 94 EXPERIMENTS IN BLUEBERRY CULTURE. Page. Fruit, pollination necessary for production ' 76 ripening process, description 78-79 Si, also Berry. Fruiting of swamp blueberry 68,81,87 Fungi, growth < 'game mailer containing no nitrates 48 m\ corrhizal, study by Charlotte Ternetz 49-50 Fungus, beneficial in rootlets 42-45, 48 50, 89 injurious, found in roots of feeble blueberry plants 64 65 Garden soil. See Soil, garden. Gaylussacia dumosa, reproduction by root stock cuttings 86 frondosa, a blue-fruited huckleberry 13 Germination of seeds 14, 51, 53 (ilass for covering s 1 flat, advantages 52 53 pots. See Pots, "lass. Goucher, Edward, grafting of swamp blueberry 83 Grafting, use in propagation S3. M No Greenfield, N. H., field plantings of blueberries 80, 87 Growth, check after transplanting, forms and causes 55-57 large, attained in pot < ulture 68 7 ! peculiarities, in the blueberry plant 14-50 root, miller various conditions 15, 17-21,23, 24,28,36,4 I. 57,66, 76 spring, in blueberry plants after wintering outdoors 71 76 stem, termination 58-59 twig, under various conditions 70. 76 vigorous under certain cultural methods 68 71 Hairs, root, absence from blueberry 40-41, 50 ordinary agricultural plants, description and function 40-41 Hardiness of blueberry plants, winter exposure 7 1 76 Heather, avoidance of limestone soils 19 n ii il fungus, study 49 Heaths, propagation, cultivation etc., citations from William McNab 63, 69, 70 Honeysuckle, swamp, occurrence in bogs and on sandy uplands 35 Huckleberry and blueberry, means of distinguishing 13 avoidance of limestone soils 19 dwarf, reproduction by rootstock cuttings 8(> name applied in New England to genus Gaylussacia 13 Humate. See Calcium humate and Magnesium humate. Humification, definition 47 Hummocks in peat bogs 36, 39, 40 Humus, definition, source of nil rales, extraction 46-47 Improvement of blueberry, discussion of methods 80-86 Indoor plants. See Plants, outdoor. Inoculation with the mycorrhizal fungus not necessary It I ii ects, capture by bog plants, nitrogen supply 50 injurious to blueberry 79 80 larvae, hastening decomposition of leaves 33 making tunnels in clay soil 24 pollen-carrying, in pollination of blueberry 7(1 78,82 Introduction to bulletin 11 II Kalmia latifolia, avoidance of limestone soils Ii' See also Laurel. peal . See Peat, kalmia. Kellerman, K. I''., on bacteria content of peal and manure 64 formulas for nutrient solutions 28t29 kalmia peat, nitrates and nitrification 46,47 Kentucky limestone soil. Se< Soil, Kentucky limestone Klamath Lake, Lower. Sir. Lower Klamath Lake. Lady's-slipper, occurrence in bogs and on sandy uplands 35 Larva'. S, i Insects, lar\ a . Laurel, avoidance of limestone soils 19 leaf deposits in formation of Maryland peal :; - ; rool fungus similar to blueberry fungus 43,44 Set also Kalmia. Layering, method of propagation of swamp blueberry 84-85 Leal buds. Si < Buds, leaf. mold. See Mold, leaf. 103 INDEX. 95 Leatherleaf bog. Set Bog, leatherli il Leaves, character on parenl plant ^<> Bl deposits in peal formation, description maple, effecl on growth of blueberry - l 25, 62 oak. aciditj testa useful in formal ion of kalmia peat 34 fully rotted, deleterious to blueberry plants 21 25 partly rotted, suited for blueberry soil 24,34 purpling, description and cause occurrence and pre> ention 17, 25, 28, 29, 60 61, 87 edling, size and shape >4 uppermost, withering and stagnation, causes 55 51 water} appearance caused by mite n . yields nearly normal solul ion of citric acid 28 Lime, injurious effects on blueberry 20, 23, 6 1 65 ■I blueberrj experiments 14,20 23,47,64 65 Limed soil. Set Soil, limed Limestone soil Set Soil, calcareous. Limewater, experiments in pot cultures of blueberry 21 22 Litter, forest, abundance of fungi present 18 i layey, mixture with sand and leaf mold, use in pot cultures 25 in pol cultures 14,25,52,54,60 Klamath Lake, peat with alkaline reaction 32 McNab, William, on culture of heaths 63,69, 70 Magnesium humate, occurrence in soils 16 17 Maine, blueberries in Boston market 12 experiments in blueberrj culture II Manure, cow, use in growing plants 1 I, 63 injurious effect on blueberry L8 19, 64 use in growing heaths and blueberry 62 I I w .Her. use in growing blueberry I Maple [eaves. Set Leaves, maple, and Woods, sugar-maple. Market requirements. Set Blueberry, market price and requirements. Marsh rosemary. Set Rosemary, marsh. Maryland peal Set Peat, kalmia. huaetts, blueberries, growth in cranberry bog 36 in Boston market L2 Matter, cellular and organic, definitions 46 Medullary rays. Set Rays, medullary. Michigan, experiments in blueberry culture II muck lands, loss of acidity alter drainage Mi ■ cope, use iu studying blueberry rootlets \l phaera alni vaccinii, mildew injurious to blueberry 79 Mddeu . injurious to blueberry, identification 79 Mite in he blueberry 80 Mixtures, soil, used in pot cultures 25,52 i. >9 I ! Mohr, I harles, on Uabama soils 19 Moisture, absorption, low rate in bog plants 50 equivalent. Set Soil, moisture measurement. freed from outside, importance as market feature 12 measurement. Set Soil, moisture measurement. requirements of seed flats 52 Set also Watering. Mold, leaf, cause of alkalinity 35 Eter long decomposition 24,35 not suited to the blueberry 24 26 proper application of name 34 ion In leal lit I er 34 Moss, Physcomitrium immersum, occurrence on alkaline leaf mold 30 num. aeration conditions satisfact tj for blueberrj in blueberrj culture..... ." 39 10 Muck, loss of acidity after drainage 35 Mulch, leaves or -and. for field plantings B8 moist leaf, effei I on growth of blueberry 24 . sufficient winter cover for blueberry plants. 71 !. for plunged pots 68 193 9G EXPERIMENTS IN BLUEBERRY CULTURE. Page. Munson, W. M., on blueberry cultivation 89 Mycorrhiza in blueberry rootlets, description and effects 42-45, 48-50, 89 ectotrophic 43-44 Myriapods, hastening decomposition of leaves 33 Nectar of the blueberry 76, 78 Neutral soil. See Soil, neutral. New Brunswick, blueberries in Boston market 12 England, occurrence of blueberry and related plants 30 Hampshire, blueberry shipments, prices received 12 Jersey, blueberries in Boston market 12 York, absence of blueberry and related plants in limestone soils 19 blueberries in Boston market 12 experiments in blueberry culture 11 Nitrates, deficiency in peaty soils I V 50 determination in kalmia peat 46 usually derived from humus 47 Nitrification, action of bacteria, nonoccurrence in acid forest litter 47, 48 Nitrifying bacteria. See Bacteria, nitrifying. Nitrites, production 47 Nitrogen, absorption from soil in form of nitrates 45 atmospheric, fixation, by bacteria 48-49 leguminous plants 48-49 root fungi 48-50 available, deficiency in peaty soil due to lack of nitrifying bacteria . 46^17 relation of blueberry fungus 48-50 determinations in kalmia peat 45, 46 ( irganic, used by fungi 48 tubercles, development on alfalfa roots 16-17 Noncalcareous soil. See Soil, noncalcareous. Normal solution. See Solution, normal. North Carolina, blueberries in Boston market 12 Nova Scotia, blueberries in Boston market 12 Nutrient solution. See Solution, nutrient. Nutrition of the blueberry, theory 50 peculiarities of the blueberry 40-50 Oak leaves and oak-leaf mold. See Leaves, oak. n K it mycorrhiza, description 44 roots, acidity test 61-62 sandy woods, presence of peal suitable to blueberry 32-35 Ohio, absence of blueberry and related plant in lirrvestone scJirs 19 ( Hiver, G. W.. method of germinating blueberry seeds 14, 51 ( hob ids. use of Mai via nd peal in growing 32 Oregon, title swamps, alkaline character of peat 32 Organic matter. Set Matter, cellular and organic. nitrogen. See Nitrogen, organic. Outdoor plants. See Plants, outdoor. Oxid, calcium. See Calcium oxid. Oxycoccus oxycoccus, rool fun mis. study 49 Pacific, humid coast sections, occurrence of blueberry and related plants 30 Parent plant. No Plant, parent. Patterson, Mrs. V. \\ . . identification of blueberry mildew - 79 Peal, acidity, causes and characteristics 31-35, 61-62 alkaline, not suited for growing blueberry 32 bacterial content, comparison with cow manure 64 bog. See r>o'_ r . peat. favorite type of acid soil for blueberry '^i~?~ fibrous dial i led. aeration conditions satisfactory for blueberry 37-38 fresh, effect on field growth of blueberry 87 excessi ve acidity ~f kalmia, description, process of formation 32-34 determinations of nitrogen and nitrates 45,46 extract ion of humus 47 moist ure conditions 37-38 nitrification not hiking place 46, 47 roots, acidity test 61-62 p.-:; INDEX. 97 aixture, experiments with roses, alfalfa, and blueberries. . . 15 r for potting plains the bog type, suitability for blueberry culture.. pure, largesl plants grown by use. .......... ... 69 suitabl berry, Bources. . 32 upland, definition I in pot cultures, discussion . 52, 5-1 56,60 62 water. Set Water, peal Peaty Boils. Set Soil, peaty. Peculiarities of blueberry. See Blueberry, peculiarities Peeling, bark of blueberry 84 Penicillin m glaucum, nitrogen fixation lit yrlvania, blueberries in Boston market 12 Phenolphthalein, use in testing soil acidity 22 I'h a, occurrence on roots of plants related to the blueberry omitrium imm currence on alkaline leaf mold Physiological dryne v Dryness, physiological. Picking, methods in use with blueberry 13-14 Pine branches. Set Branches, pine. ! esenci of peat suitable to blueberrj 32,34 Pitcher planl-. Set Plants, pitchi Pith of blueberry twigs gorged with starch. . ?6 Plain, Atlantic Coastal, occurrence of blueberries and related plants 30,37 Plant, parent, of cultivated seedlings Plants, bog, niti milation, methods. 50 occurrence on sandy upland :i. r > preservation from decaj 31 >2 dormant, erratic starting when wintered ind -s use in field plantings heath, repotting directions 70 on i door, compared with indoor plants 7 1-75 pitcher, insect food for supply of nitrogen 50 Plumpness, importance as market feature 12 Plunging, use of method 15,65 67, 67-68,68-70 Poifi us character of acid soils Si - Soil, acid Pollination, blueberry 76 Polycodium stamineum, reproduction bj rootstock cuttings 86 ilture. See < lulture, pot. lass, use in blueberry experiments 14, 15 plunging, advantages' 15, ( thumb, use for seedlin trison with Hats Potting, method with seedlings of five months 59 62 ol blueberries 12,81 Propagation, blueberry, discussion of methods Pruning blueberry, relation to method of laying down buds 71 72 Purpling of blueberry leaves, occurrence, causes, etc . . 17,25,28 Hake, use for picking blueberry 13 Raj b, medullar} . gorged with starch in blueberrj twigs. . 76 pider. Se< Spidei red Repot ting, in spring 67— < Set also Transplanting. Resting spores - s " Spores, resting Rhode (stand, experiments in blueberrj culture II Ripening, fruit, description Rool gi uting Set Grafl growth. Set < Irow th, root hair- St ' I fairs, root . Rootlets, blueberry and other plants, description 40 12 Rool , blueberrv, growth under various conditions 15, 17 21 in peat, acidity determination I inhabited bj a mycorrhizal fungus 42, 15 use of cuttings in propagation Rootstocks, blueberry, propagation of blueberry and related plants - s o 54708°— Bui 193 10 7 98 EXPERIMENTS IN BLUEBERRY CULTURE. Pago. Rose, culture in garden soil and in peal 14, 15-16, 29 Rosemary, marsh, root fungus, study 4!) Rotting of peat in blueberry culture 34,52,56,60-61,87-88 Sand, use in field plantings 88 pot cultures 25, 28, 52, 54, 60-(i L, 66 Sandstone, broken pieces, use in soil for repotting heath plants 69 70 Sandy soil. See Soil, sandy. woods. See Woods, sandy. Sarracenia, insect food for supply of nitrogen :>o Saturation, soil, effect on blueberry growth 35-36 Schott, Arthur, on shrubs in Smithsonian grounds 11 Scirpus occidentalis, forming an alkaline peat 32 Seed flats. See Flats, use for seedlings. Seedlings, blueberry, transplanting details 15, 54-57, 59-60. 67, 88 Seeds, blueberry, description and care 13, 51-54 germination 14,51,53 Selection, use in improvement of blueberries 80, 82 Shade, effect on growth of plants 55, 56, 67-68, 70-71, 88 Shipping, adaptation of the blueberry 13 Shoots, basal, development 57, 58 Smithsonian Institution, blueberry bushes in grounds 11 Soil, acid, poisonous character 45, 50 preference of blueberry and related plants 15, 17, 19, 26, 28-30, 31-32 acidity tests 22, 26-28 alkaline, deleterious to blueberry plants 26-31 phenolphthalein test, discussion and directions 26-28 bacteria. See Bacteria. blueberry, deleterious to roses and alfalfa 15-17 calcareous, absence of blueberries and related plants 19 clay, effect on growth of blueberry 24 freshly chopped, deleterious to growth of blueberries 87 garden, not suited to blueberry cultivation 11, 14-17 Kentucky limestone, absence of blueberry and related plants 19 limed, unfavorable to the blueberry 19-23 mixtures used in pot cultures 25, 52, 54, 59 62 moisture measurement 37 38 muck, loss of acidity by drainage 35 neutral, deleterious to blueberry plants 26 31 noncalcareous, occurrence of blueberry and related plants 19, 30 peaty, acid, deficiency in available nitrogen 45-46 requirements of the blueberry 11,11 Hi rich, absence of blueberry and related plants 14-17, 17-19, 30 sandy, aeration conditions satisfactory for blueberry 36-37 water-saturated, deleterious to blueberry growth 35-36 See also Loam. Solution, acid and alkaline, effect on growth of blueberrj . experiments 28-29 acidity determination 26 28 normal, definition 27 nutrient, acid and alkaline, effect on growth of blueberry 28 -"- 1 Sowing, seed of blueberry, directions 51-52 Sphagnum moss. See Moss, sphagnum. Spider, red, occurrence and control 55, 79-80 Spores, injurious, found in mots of feeble blueberrj plants 64 65 rest ing, Asterocystis radicis 65 Spring beauty, soil not good for blueberry 24 Stagnation, leaf rudiment 28, 29, 55-56, 60 Stamens of the blueberry l^~V*. March in blueberry twig's, transformation, etc 75 76 Starvation, danger" to blueberry from lack of nitrates in soil 45-46,50 Stations, agricultural experiment, attempts at blueberry culture 11 Stem gro'vt th. Se< < Irowth, stem. « ithering at tip, cause and prevention 28,55-56, 60, 70, 71 Stigma of the blueberry 77-78 Stone, broken, use in soil for reporting heath plants 69-70 Subalpine blueberry. Set Blueberry, subalpine Sugar-maple woods, S& Woods, sugar-maple. lit:: IM'IA. 99 Sundews, insecl I I for supply of aitrogeu 50 Swamp blueberry. Set Blueberry, swamp. Swarm sp in v Spores, injurious rareonemus, mite infesting the blueberry 30 rature during pot-culture experiments 53, 55, 57 absence of blueberry and related plants in limestone soils. ... 1!) Termination of stem growth 58 59 Ternetz, Charlotte on mycorrhizal fungi ii nychus bimaculatus. Set Spider, red. Theory of nutrition, blueberry 50 Thumb pol i Pots, thumb Transpiration, bog plants againsl poison in soil 50 planting, possibility, erroneous popular idea II details 15, itl l ■ , determinations of nitrogen in kalmia peat 15 Trillium, soil not L r 1 for blueberry 24, 34 Tubercles, nitrogen, development on alfalfa roots 16 17 Tule, forming an alkaline peat 32 Tu ig grow ih. See Grow th, twig , blueberry plan!, growth stoppage in early summer winter, starch large "(i i pl.mil peal > Peat upland. I plain Is. sandy, occurrence of bog plants, causes Utricularia, insecl t 1 forsupplj of nitrogi n I in in oenum, relation to V. corymbosum 82 atrococcum forcing for flowering buds, experiment 72 germination of s< eds 53 in Smithsonian grounds II laying down of flowering buds 7:; relation to V. corymbosum 82 September too late for budding 8 I stoppage of twig growth 70 canadense, sourness of berry 8] corj in I '"-nil i, experiments made principally with this species II parent plant . description 80 82 related to A atr :cum 1 1 variability 81. 82 fuscatum, identification of plant II membranaceum, produced largi st berry II pallidum, germination of seeds laying down of flowering buds 73 relation to V corj mbosum 82 use in budding 83 pennsylvanicum, fancy price for early heme- .... gl relation to possible blueberry hybrid 82 reproduction by root-stock cuttings S(j sweet ness of berry 81 vacillans, mildew abundant on 79 vitisidaea, root fungus, study in Variation, swamp blueberry seedlings R2 Varieties, blui bern . valuable, prospects Ventilation, control, for blueberries 52, 55 Wankinco, cranberry bog near Wareham, Mass . growth of blueberry Wareham, Mass., growth of blueberries in cranberry bog 3(i brown color due to acid humus r, content Set Moss, sphagnum, and Soil, moisture measurement. cull ure. See Culture, v level. v Bog blueberry, water level acidity .... 2s satisfactory nutritn e material in sand cultures source of nourishment tobogbluebi 40 saturation of soil injurious to growth of blueberry Watering, excessive, injurious to potted blueberries. . infrequent for plunged pots L93 100 EXPERIMENTS IX BLUEBERRY CULTURE. . ' Page. i ingof blueberries in pots 55 eeed bed 52 Wheat, description of root hairs 40-41 Winter, effect on young plants 74-76 Withering, stem tips, cause and prevention 55-56 occurrence 28. 60, 70, 7 1 Woods, sandy, oak or pine, source of peat suitable for blueberry 32-: J ,5 sugar-maple, rotting of leaves 84 Worms, thousand-legged, hastening decomposition of leaves :; S& also Earthworms. 193 O [Continued from page '2 of cover.] No. 107. American Root Drugs. 1907. Price, 15 cents. 108 The Cold N to rag Small Fruits. 1907. I'rlce, I ."> cents. 100. American Varieties of Garden Beans. Hhit. Price, 25 cents. 111). Cranberry Diseases 1907, Price, 20 < •nl s. 112. Use "i Suprarenal Glands in Testing Drug Plants. 1007. Price, 10 cents, 113, Comparative Tolerance ol Plants for Bnlts In Vlkall s. Tie Tuna a> r i for Man. 1907. Price, 10 cents. 117. The Reseedlng ol Depicted Range and Native Pastures. L907. Price, lo cents. us. Peruvian Alfalfa. 1007. Price, 1 nis. 119 The Mulberry and Other Silkworm-Food Plants 1907, Price, 10 cents. m>. Produi ii, ,n o1 [Coster Lllj Bulbs In the I nlted States. 1H"\ Price, LO cents. 131. Miscellaneous Papers. 1908. Price, 15 cents. 122. Curly Top: a Dlseasi of Sugar Beets, 1908. Price, 15 cents, 123. The Decaj ol Uranges while in Transit from California. 1908. Price, 20 cents. 124. The Prickly Pear as a Farm Crop. 1908 Price, 10 cents 125. Drj Land Olive Culture in Northern Africa 1908 Price, 10 cents 126. Nomenclature of the Pear. 1908 Price, 30 cents. r_'7. The Improvement of Mountain Meadows. 1908 Price, 10 cents 128. Egyptian Cdttou In the Southwestern United States. 1908. Price, 15 cots rj'.i Barium, a Cause of the Loco-W I Disease 1908 Price, 10 cents. 130 Dry Land Agriculture 1908. Price, 10 cents. 131. Miscellaneous Papers. 1908. Price, 10 cents 133. Peach Kernels, etc., .-is Bj products "i Fruil Industry. 1808. Price, 5 'ents. 134. Influence of Mixture ol Soluble Salts upon Leaf Structure and Transpiration oi Wheat, Oats, and Barlej 1908. Price, 5 cents. 135. Orchard Fruits in Virginia and the South Atlantic States. 1908. Price, 20 cents. 138. Methods and Causes of Evolution. 1008, Price, 10 cents. 137. Seeds and Plants Imported, Inventory No: 14, 1909, Price, (0 cents. 138. Production ol Cigar-Wrapper Tobacco In Connecticut Valley. 1908. Price, 15 cents. 139. Ai icau Medicinal Barks. [909. Price, 15 cents. 140. "Spineless Prickh Pears 1909. Price, 10 cents. 141. Miscellaneous Papers. 1909. Price, i<» cents. 142. Seeds and Plants Imported, Inventory No. i ■"• 1909. Price, 10 cents, 143. Principles and Practical Methods of Curing Tobacco, 1909 Price, 10 cents. ill Apple Blotch, a Serious Disease of Southern Orchards. 1909. Price, 15 cents. 145. Vegetation Affected by Agriculture in Central America. 1909 Price, 15 cents. iir. The Superiority of Line Breeding over Narrow Breeding. 1909. Price, 10 cents. 1 IT Suppressed and intensified Characters In Cotton Hybrids. 1909. Priee, 5 cents: 148. Seeds and Plants Imported. Inventory No. 16. 1909. Price, L0 cents 149. Diseases of Deciduous Forest Trees, 1909. Price, L5 cents. 150 Wild Alfalfas and i lovers ol Siberia, etc. 1909. Price, 10 cents. 161. Fruits Recommended tor Cultivation. 1909. Price, l"> cents. 152. The Loose Smuts of Barley and Wheat. 1909. Price, 15 cents. 163. Seeds and Plants Imported Inventorj No. 17. 1909". Price, L0 cents. 154. Farm Water Supplies of Minnesota. 1909. Price, 15 cents. L55. The Control of lilacs Rol of the Grape. 1909. Price. 15 cents* 156. a Study of Diversity in Egyptian Cotton. 1909 Price, 15 cents. 167 Th, • Tim i Carson Experiment Farm. 1909. Price, 10 cents, 158. The Bool Rol of Tobacco Caused by Tbielavia Basicola. 1900. Price, 15 cents. 159 Local Adjustment of Cotton Varieties. 1909. Price, Hi cuts. 160 Italian Lemons and Their By-Products, L909. Price, 15 cents. 161 A New Type of Indian Corn from China. 1910. Price, 1" cents. 162. Seeds and Plants Imported, inventory No. 18. 1910. I'i i< .-. 10 cents. 163 Varieties of American Upland Cotton. [910, Price, 25 cents. n;i Promising Rool tirops for the South. L910. Price, in cents. . 165 Application of Principles of Heredity' to Planl Breeding. 1910. Price, L0 cents. 166 The Mistletoe Pesl in the Southwest, 1910. Price, 10 cents. 161 New Methods of Planl Breeding. 1910. Price, 20 cents. 168 Seeds and Plants Imported Inventory No, 19. 1909. Price, 5 cents. [69 Variegated Alfalfa. 1010: Price.' 10 cents. iT'i Traction Plowing. 1910. Price, 10 cents. 171. Some Fungous Discs — ; "i Economic Importance. 1910. Price, '-'•"> cents. 1 7 _• Grape Investigations in Vtnifera Regions. 1910. Price, 25 cents. it:; Seasonal Nitrification as Influenced by Crops and Tillage. I9l0. Price, L0 cents. 174. The Control of Peach Brown Rol and Scab. 1910. Price, in cents. 17.".. The Hlstorj and Distribution of Sorghum. 1010. Price, 10 cents 176. Seeds and Plants Imported, inventory No. 20. 1910. Price, .". cents. ITT a Protected Stock Range in Arizona. 1910. Price, 15 cents. 178. Improvement of the Wheat Crop of California, mm. Price, 10 cents. 179. The Florida Velvet Bean and Related Plants 1910. Price, 10 cents. 180 Agricultural and Botanical Explorations In Palestine, l'.nn. Price, 15 cents. 181 Tne Curly Top of Beets. 1910. Price, 15 cents. 182. i Experienci with the Swedish Select Oat 1910. Price, 10 cents. is:: Field Studies of the Crown-Gall of the Grape 1910. Price, 10 cents. im Production of Vegetable S Is. 1910 Price, 10 cents. 185. Cold Rcststam Ifa and Some Factors Influencing It. 1910 Price, i :. c 186. Field Studies of the Cro« a Gall and Hairy Root "' the Apple Tree. I In press. I isT. Study 01 Cultivation Methods and Crop Rotation for Great Plains Area. [In press.] 188 Dry Farming in Relation to Kami. ill and Evaporation. [In press.] 180 Soun f the Drug Dloscorea, with a Consideration of the Dloscorea? Found in the I nlted Stat< b I In press, I 190. Orchard Green Manure Crops in California, I in press.] 191. val f Plrsl Generation Hybrids in Corn. I in press.] r.i_'. Drought Realstan* i the Olive In the Southwestern States. I in press.] 198 UNIVERSITY OF FLORIDA 3 1262 08929 9126