\ \ jxCAi/ / sn History Survey of Minnesota I On way MacMillan, State Botanist / A Minnesota Botanical Studies i Contents XVI. On a new registering- balance, Alex. P. Anderson XVII. On a new electrical auxanometer and continuous recorder, W. D. Frost XVTII. Titles of literature concerning the fixation of free nitrogen by plants, D. T. MacDougal "W\i, ' wei U f Bulletin No. 9 Part IV - - Sept. 27 , 1894 With four plates. 177 181 188 h MINNEAPOLIS, MINN. HARRISON & SMITH, STATE PRINTERS 1894 # framing anb f akr. LIBRARY Universityof Illinois. § CLASS. BOOK. | fe’bvsA n v ^ « VOLUME). Accession No. XYI. ON A NEW REGISTEBING BALANCE. Alex. P. Anderson. In the course of certain experiments on transpiration lately conducted in the laboratories for plant physiology of the University of Minnesota it became apparent that to .ascertain the rate of transpiration for some length of time some self registering mechanism that could be used to record the increase in the weight of the absorber was necessary. With such an appliance the periodicity (if any) in transpiration could be determined, and a true transpiration curve plotted. After repeated trials and alterations, such a registering balance has been designed consisting essentially of a balance, one arm of the beam of which is lowered by the increase in weight of the calcium chloride absorber. As this arm is lowered a circuit is closed and an electro- magnetic mechanism releases a weight which falls on the other arm of the scale beam, or rather into its scale pan. Thus the scale is balanced automatically, after an increase equal to the weight used has taken place. At the same instant that the weight is released it is recorded on the registering cylinder of the recorder, which can be at any distance from the balance itself. The scale and balancing mechanism are enclosed in a case which entirely protects the whole from fall- ing moisture. The following detailed description will serve to illustrate the action: The weighing apparatus consists of a platform scale made especially for the purpose, and to fit the registering mechanism. This scale is sensitive to one-fifteenth of a gram, with a capacity of five kilograms. It has abeam eleven inches long, the supports of which are screwed to an iron plate in the bottom of the case, thus making the scale and case practically one and both can be leveled and adjusted together. The brass scale pans are seven inches in diameter and are carried by brass supports, attached to the arms of the scale beam. The scale bearings are of diamond steel. 178 MINNESOTA BOTANICAL STUDIES. The electro-magnetic balancing mechanism consists of a weight holder and an electro- magnet, together with the contact point on the scale beam, mercury cup, wiring, batteries and the necessary fittings. The weight holder is a coiled brass tube that holds about one hundred and twenty-five weights. At the lower end of this brass coil is a lever that can turn back and forth on pivot. One end of this lever is connected by a link to the armature of the magnet, and the other end, which is held in place by a spring, when the circuit is open, has a weight pocket that takes one weight from the weight tube each time the circuit is closed and carries it laterally about five-sixteenths of an inch and lets it drop, through a hole in the brass plate,, on to the scale pan. As soon as the circuit is opened again by the readjustment of the scale beam the lever returns to its position and receives another weight from the tube, and is again ready to drop it into the scale pan as soon as the necessary increase in weight to close the circuit at the other end of the beam has taken place. The weight holder has a calibre one-sixteenth of an inch larger than the diameter of the weights used. It is screwed to the frame of the electro-magnet and extends upward and to the outside of the case for the reception of the new weights at its exterior end. It is made air and water tight from the ex- terior by means of a rubber stopper that fits into the case. The weight holder can therefore be taken out and replaced by one of greater or less calibre, depending upon the size of the weights used, thus if two tubes, five-sixteenths and one-fourth inch respectively, are used, two sets of weights can be put in, viz,: one-fourth inch weighing about one gram, and three-six- teenth inch weighing about one half a gram. Larger or smaller sizes could be used, but for growth or transpiration the above sizes are sufficiently delicate to give a good curve. The weights used are steel balls, the same make and size as are used in bicycle bearings. These are perfectly accurate, not varying in diameter more than one two thousandths of an inch, and in weight on an average not more than one thous- andth of a gram. Sets of these balls can of course be weighed and verified by the experimenter himself. The electro-magnet has a single coil, and one end of the core is joined with the frame of the magnet which forms the return magnetic circuit. The other end of the core is contracted in the form of a paraboloid. Anderson: registering balance. 179 The armature having a recess to correspond with this para- boloid, is placed between the two sides of the frame, being pivoted at one end; the other end has a lever communicating with the weight dropping mechanism by a connecting link. This construction of the magnet gives a double magnetic cir- cuit of low resistance, and also a maximum pull and greater range of movement of the armature. The current from a sin- gle good carbon-zinc cell is sufficient to operate the weight dropping mechanism. The current from the battery passes through the magnet to a mercury cup, thence through a pla- tinum contact point on the scale beam to the binding post on the case and back to the battery. The case is twelve by eighteen inches and is made of ena- melled sheet iron riveted to a frame work of wrought iron. The edges of the sheet iron are turned in so as to make with the frame work a groove on each side for two sliding glass doors. Thus the whole inside of the registering balance can be seen and watched from without, and either side of the case opened as desired. The case is leveled by means of four milled headed brass screws. A circular spirit level is placed on the iron plate immediately in front of the scale beam supports and thus the entire apparatus can be leveled in a few moments. The whole case is made so that it can be used in a green-house or in the open air without interference from moisture or rain. The registering balance can be used for registering any con- tinuous increase in weight. For transpiration a combined calcium chloride and sulphuric acid absorber is placed on one scale pan, and the previously dried air that takes up the trans- pired moisture from the plant chamber (bell glass) is forced through the absorber by means of an aspirator. Two light pieces of rubber tubing connect the absorber with the plant chamber and aspirator, by means of pieces of glass tubing in rubber stoppers fitted into the case. The rubber tubes are thus inside of the case and can not be disturbed by any outward influence. They buoy up and down with the scale pan and absorber. In balancing the scale for the beginning of an ex- periment these pieces of rubber tubing are partly weighed and continue to be a part of the weight on the absorber pan, but as their weight is approximately constant no error results. An attachment is made to the balance when used for weigh- ing large fruits, which necessarily must be grown outside of the case. This is made by elongating the scale pan support to 180 MINNESOTA BOTANICAL STUDIES. the exterior by means of a light brass tube. One scale pan will then be on the outside of the case and can be used for the growing fruit. In the preliminary experiments on transpiration this appa- ratus has been found to eliminate a large proportion of the errors usually attending this work, while it is of equal value in work on growth increase of weight. See Plate VII. XVII. ON A NEW ELECTRIC AUXANOMETER AND CONTINUOUS RECORDER. W. D. Frost. THE ELECTRIC AUXANOMETER. In undertaking recently some work on growth in thickness it was found that there was no available auxanometer suitable for the exact needs of the line of experiments designed. Pfeffer’s auxanometer was the best instrument within reach of the writer, and while this is adapted for work with moderately large plants it is too cumbersome for delicate ones, as the counter-weight required to overcome the friction of the pulleys is sufficient to produce abnormal conditions. In the measure- ment of growth in thickness of stems, fruits, etc. , it seemed absolutely necessary that the whole instrument used should be attached to, and suspended from the plant, to avoid any error caused by movements, such as twisting or bending, due to hel- iotropism or geotropism. To meet these conditions the only contrivance which seemed possible was one in which a very small increment of growth should momentarily close an electric circuit by means of some easily adjustable mechanism. The increment of growth necessary to close the circuit being constant, successive closures of the circuit could, of course, easily be registered. A working model was constructed upon this principle, and it proved so successful that it has been put in permanent shape by the instrument maker of the laboratory. It has further- more seemed advisable to print here a description of it in ad- vance of the results from its use in investigations now in pro- gress in the laboratories for plant physiology of the University of Minnesota. While it was originally intended for measuring growth in thickness, yet it is equally efficient in measuring growth in length. Its extreme lightness and delicacy make it especially useful in measuring *the growth of small plants, and since it is 182 MINNESOTA BOTANICAL STUDIES. constructed of aluminum, it can be used on plants while they are under normal conditions of moisture, without injury to the instrument. The auxanometer proper can be separated an in- definite distance from the registering apparatus. Registrations have already been made in the laboratory of the growth of plants under natural conditions, 400 yards distant and in another building. The auxanometer consists of a ratchet-wheel on a steel axis which also bears a series of small grooved wheels 1, 3-J and 6 mm. in diameter, and a somewhat larger wheel upon which is wound a thread bearing a counter-weight. The diameter of the larger wheel, is about 5 cm. and the circum- ference contains 144 notches. A ratchet which fits in the notches of this wheel, is mounted on an axis similar to that of the others, and has a long horizontal arm. This arm has a platinum tip. As the large wheel turns, the ratchet drops into the notches in its circumference and the platinum tip is lowered so that it touches a drop of mercury which is held in a small cup on the arm of the frame. This arm is insulated from the rest of the instrument and is connected by means of a small wire, to one pole of an electric battery. The other part of the instrument is connected with the other pole of the battery. The screw underneath enables the height of the mercury to be regulated, and consequently the length of time which the current remains closed or open. The frame work of the instrument is made of aluminum, and entire weighs 15 gms. It may be attached to the arm of a tripod support, and in this position can be used for measuring growth in length, (as shown in Plate x). For measuring growth in thickness the instrument can be fastened to the support and held against the stem, or fruit, which is to be measured, or it can be removed from the support and attached to the plant. When attached directly it is held in place by a clamp. This can be entirely removed and placed around the plant. It is roughly adjusted in place by means of a catch, which fits into the notches on the clamp. The fine adjustment is ac- complished by a screw. When the apparatus is in place a silk thread is fastened to the hook on the frame, passed around the plant in the direction opposite the hands of a clock, so that the thread may be in contact with the entire circumference of the plant. The thread is then passed through a hole in the axis of the auxanometer where it is securely fastened and the Frost: auxanometer and continuous recorder. 183 counter-weight on the wheel is made sufficient to keep taut the thread which passes around the plant. As the plant increases in thickness the thread is unwound from the pulley upon which it was previously wound; and as this turns, and the teeth of the large wheel pass the ratchet, the electric current is alternately opened and closed. In measuring growth in length the instrument is supported above the plant and the thread passed from the growing part to the small wheels. If the smallest wheel is used, during the growth of a millimeter, 46 registrations are made, that is to say one- forty- sixth of a mm. in length causes the circuit to be closed, while the largest wheel registers a growth of one- seventh of a millimeter. See Plate VIII. THE CONTINUOUS RECORDER. This part of the apparatus consists essentially of two rollers, one of which is attached to a clock train, and as it revolves winds upon itself a ribbon of paper on the other roller, and an electro-magnet, to the armature of which is at- tached a pen that presses against the paper on the second roller. While the circuit remains open a continuous line is traced near one edge of the paper ribbon. When the circuit is closed the pen is drawn to the other side of the paper and the length of the line traced there denotes directly the length of time that the circuit is closed. The clock train is an eight day lever movement with strong double springs. The case which is seven inches in diameter is finished in brass, and is so attached to the base that it can be easily removed. Projecting through the front of the case is the pinion by which the rollers are turned. This pinion re- volves once in twelve hours, carrying with it the roller made of brass carefully turned and balanced. It is slightly less than four inches in diameter; thus the paper moves at a rate of one inch per hour. It has quarter inch flanges, and an arrangement by which the end of the paper is held in place. On the outer surface of this roller is a dial plate with the lettering opposite to that on an ordinary clock. Upon the support is a pointer. By means of this arrangement the time indicated by the clock can be read within a few min- utes. The second roller, with the exception of the dial, is exactly similar to the first. Both are mounted on steel shafts, turned 184 MINNESOTA BOTANICAL STUDIES. to fit the bearings. The supports are made of brass and screwed to a black walnut base, which is built of narrow strips to prevent warping. The paper ribbon on which the record is obtained is two- thirds of an inch in width and made in two lengths, one suffi- ciently long to run four and the other eight days. Across the upper surface of the paper ribbon is printed a series of lines that divide the ribbon into hour spaces, which are numbered consecutively. These hour spaces are so ruled that the time of registration can be read to one minute directly from the ribbon. A source of error arising from the fact that the paper as it is wound on the first roller increases the circumference of the roller, and causes the paper to move at an increased rate as the paper continues to be wound up, is avoided by having each successive hour-space longer than the preceding one. The correction, however, is very slight on account of the thinness of the paper used, and would amount to only six minutes at the end of the eighth day. The time marker consists of a pen made of brass, and large enough to hold an amount of aniline ink sufficient for two weeks registration. This pen is attached by means of a rolled brass strip to the armature of an electro-magnet, which is hung on a hinge close to the base. Thus, as the armature moves in response to the attraction of the magnet, or the pull of a tension spring, the pen is drawn through a short hori- zontal distance. The rod simply serves as a support to the pen. The pen presses against the paper on the roller, and by means of the milled nut it can be kept at any required pressure, or can be withdrawn from the paper entirely when the latter is to be removed or replaced. When the circuit is open the armature is held back by the tension spring, and the length of the brass strip is so arranged that the pen then traces a line near the right hand side of the ribbon, as it is shown in the plate. When the circuit is closed the armature is attracted and the pen is pushed to the other side of the paper ribbon, thus making a short line at right angles to the length of the paper. If the circuit is immediately opened the time of registration is marked simply by a single cross mark. If, however, the circuit remains closed for some time a line is traced on the left side of the paper. In reading the record in this case the length of time elaps- ing between two successive closures of the circuit, is indicated Frost: AUXANOMETER AND CONTINUOUS RECORDER. 185 by the distance between the two successive forward movements of the pen, or, what is the same thing, the length of the line traced while the circuit is closed, plus the length of the line made while the circuit is open, as any one notch passes the ratchet. The auxanometer is connected with the registering appa- ratus and an electric battery. The battery is of a type suited for a closed circuit. The two instruments may be placed upon the same table, or they may be separated any distance, as is most convenient for the operator. This recorder may also be used with many other kinds of apparatus wherever a continuous record is desired. See Plate IX. XVIII. TITLES OF LITERATURE CONCERNING THE FIXATION OF FREE NITROGEN BY PLANTS. D. T. Mac Dougal. The relations sustained by plants to the nitrogen compounds of the soil and water, and to the free nitrogen of the air form a subject of great biological import, and since aside from its purely scientific aspect certain phases of the main question are of vast practical interest they have attracted the attention of the agriculturist and chemist as well as of the botanist. The results of the investigations, from these various points of view, which have been in progress for a century, form a mass of literature which is scattered through the journals and pro- ceedings of the various branches of natural science in such manner as to be very difficult of access to the student with ordinary facilities. Among this rich and withal unwieldy mass of literature the part of especial interest to the botanist is that which concerns the fixation of free nitrogen by the leguminous plants and the organism found in the tubercles which characterize this group, and the fixation of free nitrogen by green plants which do not sustain mutualistic relations to the lower organisms. The large number of controversies resulting from the attain- ment of radically different conclusions from similar experiments along certain lines of the work, in the hands of various investi- gators, leads to the belief that safe generalizations can be made from the restricted groups of facts thus obtained only when confirmed by extended and parallel researches. To meet this idea the references given below concern the points of central interest to the botanist, beside a number of titles to ‘ ‘ nitrifica- tion,” and to cases of mutualism and symbiosis which may * offer a comparison however distant with the relations existing between the leguminous plant and the tubercle organism. Mac Dougal: fixation of free nitrogen. 187 The list is composed of titles which have been incidentally collected by Professor MacMillan and the writer, and are com- prised in the card catalogue of the botanical department of the University of Minnesota. Their presentation in this form is for the purpose of making them still more readily available to students and investigators in connection with this department, and wherever this line of work is carried forward. It is pur- posed to bring out a second installment of titles which the writer in the limited time at his disposal was not able to prepare for this number. Allen E. W. Leguminous plants for green manuring and for feeding. U. S. Dept. Ag. Farm. Bull. No. 16. 1894. Lllpe and Menozzi. Bull. d. notize agrarie d. Ministere d’ Agric. No. 14. 1892. Andre. See Berthelot. -Arcangeli. Sopra i tubercoli radicali delle Leguminose. Atti del. real. Accad. d. Lincei, 7 : Fasc. 6, 223. 1891. ■ Atkinson G. F. Scien ce Coni Ala. Ex. Sta. 1 : 1. 1889. t Atkinson G. F. The genus Frankia in the United States. Bull. Torr. Bot. Club 19: 171 1892. Atkinson G. F. Tubercles of Ceanothus. Bot. Gazette 16:262. 1891. ‘'Atkinson G. F. Contributions to the biology of the organism causing leguminous tubercles. Bot. Gazette 18:157, 226,257. 1893. Atkinson G. F. Symbiosis in the roots of the Ophioglossaceae. Bull. Torr. Bot. Club 20 : 356. 1893. Atwater and Rockwood. On the loss of nitrogen during germ- ination and growth. Am. Chem. Jour. 8 : 327. 1868. Atwater W. 0. On the assimilation of atmospheric nitrogen by plants. Rep. Brit. A. A. S. 685. 1884. ^Atwater W. 0. Absorption of atmospheric nitrogen by plants. Am. Chem. Jour. 6:365. 1885; also, 12:526. 1891^; also, 13:42. 1891. i-Atwater and Woods. Atmospheric nitrogen as plant food. Conn. Storrs Ag. Ex. Sta. Rep. 2:11. 1889; also, 3:12. 1890. Atwater and Woods. The fixation of free nitrogen by plants. Conn. Storrs Ag. Ex. Sta. Rep. 5:17. 1892. Atwater W. 0. On the liberation of nitrogen from its com- pounds, and the acquisition of atmospheric nitrogen by plants. Am. Chem. Jour. 8: 398. 1868. 188 MINNESOTA BOTANICAL STUDJES. Atwater and Woods. Absorption of atmospheric nitrogen by" plants. Am. Chem. Jour. 13:42. 1891. Babes* Cornil et. Bacteries du sol. Les Bacteries, 1:213. 1890. Bary A. de Morphologie und Physiologie der Pilze, Flechten und Myxomyceten. 1866. Bary A. de Die Erscheinung der Symbiose. 1879. Benecke F. Ueber die Mykorhiza. Biol. Centralb. 4:753, 781. 1888. Benecke F. Ueber die Knollchen an den Leguminosen-Wurz- eln. Bot. Centralb. 29*: 53. 1887. ' Berg F. Das nitrificierende Ferment des Bodens. Sitzungsb. Naturf. Ges. Dorpat. 10: No. 1. 1892. Berggren S. Om rotbildningen hos australa Coniferer. Bot. Notiser. 144. 1887. Berthelot. Sur l’absorption de l’azote libre par les principes immediats des vegetaux sous l’inlluence de l’electricite. Jour. f. Pharm. 24:433. 1876. Berthelot. Sur l’absorption de Tazote libre par les principes immediats des vegetaux sous l’influence de l’electricite atmospherique. Compt. rend. 83:677. 1876. Berthelot. Sur l’absorption de l’azote libre par les principes immediats des vegetaux sous l’inlluence de l’electricite. Ann. d. Chim. et Phys. 10: 55. 1877. Berthelot and Andre. “Nitrates in plants.” Jour. f. Pharm. _ et Chim. 1884. Berthelot. Fixation directe de l’azote atmospherique libre par certaines terrains argileux. Compt. rend. 101: 1885. Berthelot and Andre. Sur les principles azotees de la terre vegetaie. Compt. rend. 103:1101. 1886. Berthelot. Sur la fixation directe de l’azote gazeux de l’atmos- phere par les terres vegetales. Compt. rend. 104:205. 1887. Berthelot. Sur la fixation de 1’azote gazeux de 1' atmosphere par les terres vegetales, avec le concours de la vege- tation. Compt. rend. 104:625. 1887. Berthelot. Experiences nouvelles sur la fixation de l’azote et par certaines terres v6g6 tales et par certaines plantes. Compt. rend. 106:372. 1888. Berthelot. Sur quelques conditions generates de la fixation de l’azote par la terre vegetaie. Compt. rend. 106: 569. 1888. Mac Dougal: fixation of free nitrogen. 189 Berthelot. Sur la transformation dans le sol des azotates en composes organiques azotes. Compt. rend. 106:638. 1888. Berthelot. Observations snr la fixation de l’azote par certaines sols et terres vege tales. Compt. rend. 106: 1049. 1888. Berthelot. Sur la fixation de l’azote par la terre vegetale. Compt. rend. 106:1214. 1888. Berthelot. Experiences nouvelles sur la fixation de l’azote par . certaines terres v^getales et par certaines plantes. Ann. d. Chim. et Phys. 16. 1889. Berthelot and Andre. Faits pour servir a l’histoire des prin- cipes azotes renfermes dans la terre vegetale. Ann. d. Chim. et Phys. 6 ser. 2 5 : 314. 1892. Berthelot. Sur la fixation de l’azote dans les oxydation len- tes. Compt. rend. 108:543. 1889. Berthelot. Fixation de 1’ azote par la terre vegetale nue ou avec le concours des Legumineuses. Compt. rend. 108:700. 1889. ^Berthelot. Recherches nouvelles sur la fixation de l’azote par la terre vegetale. Influence del electricite. Compt. rend. 109:281. 1889. ^Berthelot. Sur les relations de l’azote atmospherique avec la terre vegetale. Compt. rend. 109: 345. 1889. v Berthelot. Sur la fixation de l’azote atmospherique. Compt. rend. 109:417. 1889. ^Berthelot. Observations sur la formation de l’ammoniaque et de composes azotes volatils aux depens de la terre vegetale et des plantes. Compt. rend. 109:419. 1889. 1 Berthelot. Remarques sur la formation des azotates dans les vegetaux. Compt. rend. 110: 109. 1890. -Berthelot. Observations sur la note precedente de Schloesing fils et Em. Laurent. Compt. rend. Ill : 753. 1890. Berthelot. Observations sur les reactions entre la terre vege- tale et l’ammoniaque atmospherique. Compt. rend. 111:558. 1890. Berthelot and Andre. Faits pour servir a l’histoire des prin- cipes azotes renfermes dans la terre v6g6tale. Compt. rend. 112:189. 1891. Berthelot. Nouvelles recherches sur la fixation de l’azote par les microbes. Compt. rend. 115: 569. 1892. ^Berthelot. Recherches nouvelles sur les micro- organismes fixateurs de l’azote. Compt. rend, 116:842. 1893, 190 MINNESOTA BOTANICAL STUDIES. Berthelot. Observations relativus a une note de Winograd- sky Snr l’assimilation de l’azote gazeux de l’atmosphere par les microbes. Comp t. rend. 116:1388. 1893. Berthelot. Nouvelles recherches snr les micro- organismes fixateurs de l’azote. Ann. d. Cfrmi, et Phys, 30:419. 1893. Berthelot. Nouvelles recherches sur la fixation de l’azote atmospherique par les micro- organismes. Ann. d. Chim. et Phys. 30:411. 1893. Berthelot. Sur une methode destinee a etudier les echanges gazeux entre les etres vivants et l’atmosphere que les entoure. Compt. rend. 118 : 112. 1894. Berthelot. Nouvelles observations sur les composes azotes volatils emis par la terre vegetale. Compt. rend. 118:195. 1894. Beyerinck M. W. Die Bacterien der Papilionaceen-knOllchen. Bot. Ztg. 46:725, 741, 757, 780, 797. 1888. Beyerinck M. W. Wurzelknospen. Verh. d. koninkl. Akad v. Wetensch. te Amsterdam. 25 : — . 1887. See also 1890. Beyerinck M. W. Kunstliche Infektion von Vicia faba mit Bacillus radicicola: Ernahrungsbedingungen dieser Bacterie. Bot. Ztg. 48:838. 1890. Beyerinck M. W. Over ophooping van atmospherische Stick- stoff in culturen van Bacillus radicicola. Vers, en Meded. der koninkl. Akad. van Wetensch. te Amster- dam. Afd. Natuurkunde, Hft. 3:460. 1891. Bohme K. Stickstoff-ernahrung der Leguminosen. Separat 1892. Dresden. Bolley H. B. Notes on root tubercles of indigenous and exotic Legumes in virgin soil of Northwest. Ag. Science 7 : 58. 1893. Bonnier G. La Constitution des Lichens. Jour. d. Bot. 1: 1. 1887. Bonnier G. Germination des spores de Lichens sur les proto- nemas des Mousses. Rev. Gen. d. Bot. 1 : 165. 1889. Bonnier G. Recherches sur la synthese des Lichens. Ann. d. Sc. Nat 7ser. 9 :1. 1889. Bonorden H. F. Handbuch der Allgemeinen Mykologie. 1851. Bordier M. H. “Nitrification.” Mem. Sc. Phys. et Nat. Bor- deaux 5:185. 1890. Borgreve. Zusatz zu: Braun zur Mycorhiza Frage. Forstl. Bl. 13:205. 1889. Mac Dougal: fixation of fjree nitrogen. 191 t Bouche. Zur Unterscheidung des Phaseolus vulgaris und Ph. multiflorus Lam. Bot. Ztg. 10:735. 1852. 'Boudier. Du parasitisme probable de quelques especes du genre Elaphomyces et de la recherche de ces Tuber- aces. Bull. d. Soc. Bot. d. France, 23: — . 1876. Bouquet. Eine neue Hypotheses des Absorptions der Stick- stoff durch Pflanzen. Jour. l’Ag. Practique. 1888. Boussingault J. B. Recherches chimiques sur la vegetation enteprises dans le but d’examiner si les plantes pren- nent de l’azote de l’atmosphere. Ann. Sc. Nat. 10:257. 1837. Boussingault J. B. Recherches chimiques sur la vegetation enterprises dans le but d’examiner si les plantes pren- nent de l’azote de l’atmosphere, Compt. rend. 6 : 102. 1838 and 7 : 138. 1838. Boussingault J. B. Recherches chimiques sur la vegetation enteprises dans le but d’examiner si les plantes pren- nent de l’azote de l’atmosphere, Ann. d. Chim. et Phys. 67:35. 1838 and 69:353. 1838. Boussingault J. B. Recherches chimiques sur la vegetation enteprises dans le but d’examiner si les plantes pren- nent de l’azote de l’atmosphere, Jour. f. Prakt. Chem. 14:193. 1838, and 16:385. 1839. '^Boussingault J. B. Recherches sur la vegetation, etc. Ann. d. Chim. 41:5. 1854, and 43: 149. 1855. ^ Boussingault J. B. Recherches sur la, vegetation, etc. Ann. Sc. Nat. 1:241. 1854. Boussingault J. B. Recherches sur la vegetation, etc. Jour, d. Pharm. 26:127. 1854. 'Boussingault J. B. Recherches sur la vegetation. Compt. rend. 38: 580, 607. 1854, and 39: 601. 1854. Boussingault J. B. Recherches sur la vegetation. Ann. d. Chim. 46:5. 1856. Boussingault J. B. Recherches sur la vegetation. Ann. Sc. Nat. 2:357. 1854. wBoussingault J. B. Recherches sur la vegetation. Jour f. Prakt. Chem. 62:108, 181. 1854, and 63:418. 1854. Boussingault J. B. Recherches sur l’influence que l’azote assimilable des engrais exerce sur la production de la matiere vegetale. Compt. rend. 44:940. 1857, and 45:833. 1857. 192 MINNESOTA BOTANICAL STUDIES. Boussingault J. B. Recherches sur l’influence que l’azote assimilable des engrais exerce sur la production de la matiere vegetale. Ann. Sc. Nat. 7 : 5. 1857. Boussingault J. B. Agronomie, Chemie, Agricole et Phy- siologie 1 : 198. 1860, and 2 : 340. 1861. Boussingault J. B. Sur la nitrification de la terre Vegetale. Compt. rend. 76:22. 1873. Boussingault J. B. Sur la nitrification de la terre vegetale. Ann. d. Chim. et Phys. 29:186. 1873. Boussingault J, B. Sur l’influence que la terre vegetale exerce sur la nitrification des substances azotes d’origine or- ganique employees comme engrais. Compt. rend. 82:477. 1876. Also, Ann. d. Chim. 8:5. 1876. Boutin. Note sur l’origine des nitrates dans l’Amarantus bli- tum. Compt. rend. 82: No. 25. 1876. Boutroux L. Sur la fermentation panaire. Compt. rend. 112: 203. 1891. See also Ann. d. Chim. et Phys. 1892. 'Boutroux L. Reveux des travaux sur les bacteries et les fer- mentations. Rev. Gen. d. Bot. 1 6 : 30. 1894. Bowman J. E. On the parasitical connection of Lathraea squamaria and the peculiar structure of the subter- ranean leaves. Trans. Linn. Soc. 16:399. 1833. Braun. Zur Mycorhiza Frage. Forstl. Bl. 13: 204. 1889. ^Breal E. Ann. Agron. 1888. ^Breal E. Observations sur la fixation de l’azote atmos- pherique par les Legumineuses dont les racines portent des nodosites. Compt. rend. 107:372. 1888. ^Breal E. Fixation de l’azote par les Legumineuses. Compt. rend. 109:670. 1889. 110:670. 1890. Breal E. Bindung des Lufts ticks toffs durch Kresse (Tropae- olum). Ann. Agron. 18:369. 1893. Brefeld 0. Bot. Untersuchungen. 1883. Brefeld 0. Untersuchungen auz dem Gesammtgebiete der Mykologie, 3. 1877. And 7. 1888. Bruchmann H. Ueber Anlage und Wachstum der Wurzeln von Lycopodium und Isoetes. Jen. Zeitschr. f. Naturw. New Ser. 1 : 522. 1874. Bruchmann H. Die Dichotomie der Wurzel von Pinus sylves- tris. Jen. Zeitschr. f. Naturw. New Ser. 1:572. 1874. Bruchmann H. Das Prothallium von Lycopodium. Bot. Cen- tralb. 21:23, 309. 1885. Mac Dougal: fixation of free nitrogen. 193 Brunchorst B. Ueber die Knollchen an der Wurzeln von Alnns nnd den Eleagnaceen. Bot. Centra lb. 24: 222. 1885. Brunchorst B. Ueber die Knollchen an den Leguminosen- wnrzeln. Ber. d. deut. Bot. Ges. 3: Hft. 7, 241. 1885. v Brunchorst B. Ueber einige Wurzelanschwellungen, besond- ers diejenigen von Alnus and Elaeagnaceen. Unter- such. Bot. Inst. z. Tubingen, 2:151. 1886. Brunchorst B. Die Struktur der Inhaltskftrper in den Zellen einiger Wurzelanschwellungen. Sep. a. Bergens Mus. Arsberetning. 235. 1887. » Buscalioni, Si contengono bacteri nei tubercoli radicati delle Leguminose. Malphigia 1 : 21, 464. 1887. *Cloez S. Recherches experimentales sur la nitrification et sur la source de l’azote dans les plantes. Compt. rend 41:935. 1855. ~Uloez S. Lettre a M. Chevreul concernant les experiences de M. Yille sur la question de l’assimilation de l’azote de l’air par les vegetaux. Compt. rend. 41:775. 1855. aUIocz S. Recherches experimentales sur la nitrification et sur la source de l’azote dans les plantes. L’lnstitute 23: 417. 1855. Cloez S. Recherches experimentales sur la nitrification et sur la source de l’azote dans les plantes. Jour. f. Prakt. Chem. 68:138. 1856. Cloez 8. See Gratiolet. , Clos D. Ebauche de la rhizotaxie 1848. Paris. Clos D. Du collet dans les plantes et de la nature de quelque tubercles. Ann. d. Sc. Bot. 3: 13. 1849. vClos D. Du collet dans les plantes et de la nature de quelques tubercules. Ann. Sc. Nat. 13:5. 1850. See also Soc. Philom. Proc. Verb. 34. 1850. MDlos D. Revision des tubercles des plantes et des tuberculoides des Legumineuses, Mem. d. l’Acad. d. Toulouse 9 ser. 5. 1. 1893. ^Canevari A. La nutrizione delle piante il terreno e la conci- mazione, L’ltalia agricolia 1 9. 1887. ^Chevreul E. Sur le role de l’azote atmosph^rique dans 1’economie vegetale. Compt. rend. 107:1460. 1888. v*Chuard E. Sur V existence de phenom^nes de nitrification dans les mileux riches en substance organiques et a reaction acids. Compt. rend. 1 14 : 181. 1892. 194 MINNESOTA BOTANICAL STUDIES. iCOhn F. Ueber parasitic Algen. Beitr. z. Biol. 1 : Hft. 2 : 87. 1872. Cohn F. Zur Geschichte der Leguminosenknollchen. Centralb. f. Bakt. u. Par-Kunde. 10 : No 6, 190. 1891. “ Coignet J. De l’absorption de l’azote par les vegetaux. Ann. d. 1. Soc. d’agr. d. Lyon, 5 Ser. 2 : 233 . 1888. 'Condamy A. Etude sur l’histoire naturelle de la Trufiie. 1876. Conn H. W. Nature of the root tubercles of leguminous plants. U. S. Ex. Sta. Rec. 2:686. 1890 and 1891, and 3 : 56. 1891 and 1892. vConn H. W. Free nitrogen assimilation. Bull. Torr. Bot. Club 20: 148. 1893. Corda A. K. J, leones Fungorum hucusque cognitorum. 1837, 1854. ^Cornil et Babes. Bacteries du sol. Les Bacteries 1:213. 1890. Cornu. Commission du Phylloxera. 1876. Cornu. Etudes sur le Phylloxera vastatrix. 1878. Coudon Muntz, and La fermentation ammoniacale de la terre. Ann. Agron. 1 9 : 209. 1893. vCrochetelle et Dumont. Sur la nitrification des terre de prairie, Compt. rend. 117:670. 1893. i Dangeard. Note sur les Mycorhizes endtropiques. Le Botan- iste Ser. 2, 223. 1891, De Candolle. Prodromus Syst. Nat. Reg. Veg. 2:312. 1825. Deherain P. P. Sur l’absorption de l’azote par les plantes. Bull. Soc. Chim. 16:2. 1871. Deherain P. P. Sur l’intervention de 1’ azote atmospherique dans la vegetation. Compt. rend. 7 3 : 1352. 1891. And 76:1390. 1873. Deherain P. P. Sur l’intervention de l’azote atmospherique dans la vegetation Bull. Soc. Chim. 1 9 : 538. 1873. Deherain P. P. Sur Intervention de l’azote atmospherique dans la vegetation. Jour. d. Pharm. 18: 95. 1873. ‘"Deherain P. P. Sur l’intervention de l’azote atmospherique dans la vegetation. Ann. Sci. Nat. 5 Ser. 18:147. 1873. • Deherain P. P. Sur l’intervention de l’azote atmospherique dans la vegetation. Chem. News. 29:271. 1874. Deherain P. P. Sur l’enrichessement en azote d’un sol main- tenu en prairie. Compt. rend. 101 . 1885. ^Deherain P. P. Le travail du sol et la nitrification. Ann Agron. 19:401. 1893. Mac Dougal: fixation of free nitrogen. 195 ^Deherain P. P. Le travail de la terre et la nitrification. Compt. rend. 116:1091. 1893. l /Delpino. Osservazioni sopra batteriocecidii la sorgente l’azote in una piante-Galega officinalis. Malphigia 2 : 385. 1888. Saussure. Recherches sur la vegetation. 206. 1804. HDetmer. Physiol. Chem. Unters. uber Keimung 68. 1875. >dDevaux. Circulation passive de l’azote dans les vegeta ux. Jour. d. Bot. 5:130. 1891. "Devaux. Les echanges gazeux d’un tubercle, representes schematiquement par un appareil physique, Bull. Soc. Bot. d. France. 37:257. 1891. Devaux. Atmosphere interne des tubercules et racines tuber- culeuses. Bull. d. Soc. Bot. d. France. 37:272. 1890. De Yogue. Fixation de l’azote ammoniacal sur la paille. Compt. rend. 1 1 5 : 25. 1892. /^De Tries. Wachstumgeschichte des roten Klees. Landw. Jahrb. 6:933. 1877. v-Douliot et van Tieghem. Recherches comparatives sur l’origine des membres endogenes dans les plantes vas- culaires. Ann. d. Sc. Nat. 7 Ser. 8:1. 1888. Drouin. See Gautier. Duchartre P. Note sur l’Hypopitys multiflora Scop. Ann. d. Sc. Nat. 3 Ser. 6:29. 1846. Duclaux. La distribution de la matiere organique et des microbes dans le sol. Ann. Inst. Past. 7 : 823. 1893. « Duhamel du Moneeau. La Physique des Arbres. 1758. Dumont et Crochetelle. Sur la nitrification des terres de prairie. Compt. rend. 117:670. 1893. Drobnig. Beitrage zur Kenntniss der WurzelknSllen. Inaug. Diss. 1892. Rbstock. Drude 0. Die Biologie von Monotropa Hypopitys L. und Neot- tia Nidus avis L. 1873. Gottingen. i Kamienski Fr. Ueber symbiotische Vereinigung von Pilzmy- celium mit den Wurzeln hoherer Pflanzen. Arbeit, d. St. Petersb. Naturf. Ges. 17:34. 1886. Keller. Die Wurzelknollcheh der Leguminosen. Biol. Cen- tralb. 9:97. 1889. 1 Kellner 0. Ueber den Gehalt einiger Wurzelgewachse an Stickstoffhaltigen Nicht-Proteinstoffen. Deut. Landw. Presse No. 82. 1880. ^Kellner und Yoshii. Ueber die Entbindung freien Stickstoffs bei der Faulniss und Nitrification. Zeitschr. f. Phys. Chem. 12:95. 1888. ^Kerner von Marilaun A. Schmarotzer, etc. Pflanzenleben 1: # 52, 59, 147, 224, 553, 556, 695, 711, 728, 729, 730. 1890 Also 2:77, 83, 445. 1891. Mac Dougal: fixation of free nitrogen. 203 Kionka H. Die WurzelknSllchen der Leguminosen. Biol. Centralb. 1 1 : 282. 1891. v Klebahn H. Die neuesten Untersuehungen uber die Wurzel- knSllchen. Humboldt 148. 1890. uXlein und Szabo. Zur Kenntniss der Wurzeln von Aesculus hippocastaneum L. Flora 63:147, 163. 1880. v Kny L. Ueber parasitische Algen. Bot. Ztg. 31:139. 1873. Kny L. Ueber die Wurzelanschwellungen der Leguminosen und ihre Erzeugung durch Einfluss von Parasiten. Sitzungsber. d. bot. Yer. d. Prov. Brandenburg 21:55. 1879. ; Kny L. Zu dem Aufsatze des Herrn Prof. B. Frank “Ueber Parasiten in den Wurzelnanschwellungen der Papil- ionaceen.” Bot. Ztg. 37:537. 1879. tXny L. Ueber eigenthiimlich Durchwachsungen an den Wur- zelhaaren zweier Marchantiaceen, untersucht von Dr. Bottger. Sitzungsber. d. Prov. Brand. Jan. 1879. ^Koch und Mayer. Ueber die Aufnahme von Ammoniak durch oberirdische Pflanzentheile. Bied. Centralb. f. Landw- Sept. Hft. 1873. iJKoch A. Zur Kenntniss der Faden in den WurzelknSllchen der Leguminoseen. Ber. d. deut. Bot. Ges. 5: 111. 1887. K&ock A. Zur Kenntniss der Faden in den Wurzelknollchen der Leguminoseen. Bot. Ztg. 48:597. 1890. ‘"Koch und Kossowitsch. Ueber die assimilation von freien Stickstoff durch Algen. Bot. Ztg. 51:321. 1893. -Koenig. Stickstoff Vorrat. 1887. Kolaczek. Lehrbuch der Botanik. 3741. 1856. ‘•Xossowicz. Die Herkunft des Stickstoffs in den Pflanzen. Mitth. Landw. Akad. zu Petrowsky 13:61. 1890. ""Kossowitsch P. Durch welche Organe nehmen die Legumi- nosen den freien Sticksotff auf. Bot. Ztg. 50:697, 713, 729, 745, 771. 1892. Kossowitsch P. Untersuehungen ueber die Frage ob die Algen freien Stickstoff fixiren. Bot. Ztg. 52:97. 1894. ^Kostycheif. “The formation and properties of vegetable mould.” St. Petersburg Soc. Nat. Bot. 20:123. 1889. i-Xuhn Y. R. Untersuehungen uber die Anatomie der Marattia aceen und andere Gefass-Kryptogamen. Flora 7 2 : 457. 1889. Lachmann J. Ueber KnQllchen der Leguminosen. Landw Mittheil. Zeitschr. d. K. Lehranstalt und Versucht sta 37. 1856. 204 MINNESOTA BOTANICAL STUDIES. Lachmann J. Knollen an den Wnrzeln der Leguminosem Chem. Centralb. No. 18. 1892. Laurent E. Sur le microbe des nodosites des Legumineuses. Compt. rend. 111:750. 1890. Laurent E. Experiences snr la production des nodosites chez. le pois a la suite d’inoculations. Bull. d. 1. Acad. Roy. d. Belgique 3 Ser. 1: No. 6. 764. 1890. ^Laurent E. Experiences sur la reduction des nitrates par les vegStaux. Ann. Inst. Past. No. 7:22. 1890. Laurent E. Recherch.es sur les nodosites radicles. Ann. Inst. Past. 5:105. 1891. -Laurent E. Experiences sur la reduction des nitrates par les vegetaux. Rev. Mycol. 16:25. 1894. Laurent. See Schloesing. >Lawes and Gilbert. On the present position of the question of the sources of nitrogen in vegetation, with some new results, and preliminary notice of new lines of investi- gation. Proc. Roy. Soc. 42: No. 256. 1886. i-Lawes, Gilbert and Pugh. Assimilation of nitrogen by plants. Rep. Brit A. A. S. 51. 1852. ‘-Lawes and Gilbert. On the sources of the nitrogen of vegeta tion, with special reference to the question whether plants assimilate free or uncombined nitrogen. Proc. Roy. Soc. 10:544. 1859-60. ^Lawes and Gilbert. On the sources of the nitrogen of vegeta- tion, with special reference to the question whether plants assimilate free or uncombined nitrogen. Phil. Trans. 431. 1861. Chem. Soc. Journ. 1:100. 1863. Lawes and Gilbert. On assimilation of nitrogen. Chem. News, 6:127. 1863. ^Lawes and Gilbert. Assimilation of nitrogen by plants. Journ. d. Pharm. 44:281. 1863. ^Lawes and Gilbert. Sources of nitrogen in vegetation. Proc. Roy. Soc. 43:108. 1887. ^Lawes and Gilbert. On the present question of the sources of nitrogen in vegetation, etc. Phil. Trans. Roy. Soc. London, 180:1-107. 1888. ^Lawes and Gilbert. Fixation of free nitrogen. Proc. Roy. Soc. 47: No. 1, 85. 1890. KLawes and Gilbert. New experiments on the question of the fixation of free nitrogen. Proc. Roy. Soc. Bond. 47 : 85. 1890. Mac Dougal: fixation of free nitrogen. 205 .Lawes and Gilbert. Experiments on root tubercles and the fixation of atmospheric nitrogen. Abth. f. Ag. Chem. u. Landw. Ver. d. Ges. deut. Naturf. u. Aerzte. Halle. Sept. 1891. ^Lawes and Gilbert. Sources of nitrogen in leguminous plants. Jour. Rev. Ag. Soc. 8 Ser. 2 : 657. 1892. LeComte H. Note sur le Mycorhiza, Bull. d. Soc. Bot. d. France 3 4 : 30. 1887. ,Leone und Magnaninii. Nitrification des organischen Stick- stoffs. Chem. Centralb. 1 : No. 5. 1891. Mattirolo 0. Sur le parasitisme des truffes etsur la question des Mycorhiza. Arch. Ital. Biol. 9:218. 1888. < Mattirolo 0. Sur le parasitisme des truffes et sur la question des mycorhizes. Arch. Ital.d. Biol. 9. 1888. ’■'Mayer A. Lehrbuch der Agriculturchem. 3rd Ed. 1:163. . McMurtrie. Notes on absorption of nitrogenous nutriment by the roots of plants. Proc. Brit. A. A. S. 139. 1887. HMene C. Experiences sur l’influence d. gaz dans la vegeta- tion, Dingier poly tech. Jour. 119:453. 1851. ^Mene C. Experiences sur l’influence du gaz azote dans la vege - tation. Compt. rend. 32:180 1891. -Menozzi. See Alpe. -Merker P. Gunnera macrophylla Blum. Inaug. Diss. Mar- burg, 1888. Flora 72: 211. 1889. Meyen J. Ueber das Hervorwachsen parasitischer Gebilde aus den Wurzeln anderer Pflanzen. Flora 12:49. 1829. JMeyer A. Ueber die Knollen der einheimischen Orchideen. Archiv. d. Pharmacie 24. 1886. "Milde. Notizen zur Kenntniss von Anthoceros und Blasia. Bot. Ztg. 9:629. 1851. 208 MINNESOTA BOTANICAL STUDIES. Miles. Die nitrifizirenden Mikrpben, Chem. Centralb. No 47. 1887. Miles. Biological factors in the nutrition of farm crops. Proc. A. A. A. S. 433. 1890. Millon E. Nitrification. Chem. News 2: No. 56. 263, 337. 1860. See also Compt. rend. 1 7 : 452, 470. Millon E. Theorie chimique de la nitrification. Jour. d. Pharm. 88:325. 1860. Millon E. Note sur la nitrification, etc. Compt. rend. 51:819. 1860. ^Millon E. De la nitrification en la Algerie. Jour, de Pharm. 38:246. 1860. ' Millon E. Theorie chimique de la nitrification. Compt. rend. 51:548.- 1860. ^Millon E. Theorie chimique de la nitrification. Chem. News 2:337. 1860. Millon E. Nitrification. Chem. News. 82. 1864. Moebius. Ueber endophytic A1 gen. Biol. Centralb. 11:546. 1891. Moebius. Conspectus algarum endophyticum. La Notarisia 6: 1221, 1279, 1291. 1891. ^ Moeller H. Plasmodiophora Alni. Ber. d. deut. Bot. Ges. 3: 102. 1885. Moeller H. Beitrag zur Kenntniss der Frankia subtilis. Brunch. Ber. d. deut. Bot. Ges. 8:215. 1890. 1 Moeller H. Bemerkungen zu Frank’s Mittheilung urber den Dimorphismus der Wurzelkn5llchen der Erbse. Ber. d. deut. Bot. Ges. 10:242. 1892. ■"Moeller A. Ueber die Cultur fiechtenbildener Ascomyceten ohne Algen. Inaug. Diss. Munster. 1887. hMorck. Ueber die Formen der Bakterioiden bei der einzelnen spezies der Leguminosen. Inaug. Dissert. 1891. Leipzig. L Morren C. Experiences sur l’absorption de l’azote par les ani- malcules et les algues. Compt. rend. 38:932. 1854. "Morren C. Experiences sur l’absorption de l’azote par les ani- malcules et les algues. Ann. Soc. Nat. (Zool. ) 1:339. 1854. Mulder G. H, Ueber die condensation des Stickstoffs aus der Atmosphare in der Ackererde und ueber das Ernah- rungsvermogen der organische Bestandtheile des Bodens fur die Pflanze. Jour. f. Prakt. Chem. 32: 344. 1844. Mac Dougal: fixation of free nitrogen. 209 Mulder G, H, Ueber die Quelle des Sticks toffs in den Pflanzen . Flora 28:239. 1845. Mulder G. H. Van Waar bekommen die niet b ernes te plan ten hare Stickstoffs. Amsterdam. Verslag. 3 : 61. 1855. Mulder G, H, Versuch einer Phys. Chem. 751. Muller P, E, Bemerkungen ueber die Mycorhiza der Buche. Bot. Centralb. 2 6 : 22. 1886. Muntz, See Schloesing. Muntz A. De quelques faits d’ oxydation et de reduction, produits par les organismes microsc. du sol. Journ. d. Pharm. et d. Chem. 5 Ser. 12: No. 6. 1885. Muntz and Marcano. Sur la formation des terres nitrees dans les regions tropicales. Journ. d. Pharm. et d. Chem. 5 Ser. 12: No. 6. 1885. Muntz A. Ueber einige Oxidation und Reduction durch Mik- roorganismen im Boden. Chem. Centralb. No. 37. 1885. Muntz A. Ueber d. Bildung d. saltpeterhaltigen Erden in den Tropen. Chem. Centralb. No. 37. 1885. Muntz A. Sur la decomposition des engrais organiques dans le sol. Compt. rend. 110:1206. 1890. Muntz A. Sur la decomposition des engrais organiques dans le sol. Compt. rend. 110: 1026. 1890. Muntz A. Du role des engrais verts comme furnures azote^s. Compt. rend. 110:972. 1890. Muntz A. Sur la formation des nitrates dans la terre. Compt. rend. 112:1142. 1891. Muntz A. Sur la formation des nitrates dans la terre. Compt. rend. 112:1143. 1891. -Muntz and Coudon. La fermentation ammoniacale de la terre. Ann. Agron. 1 9 : 209. 1893. '-N. H. J. M. The fixation of free nitrogen. Nature, 24:41. 1890. -Naegeli. Botanische Beitrage: Pilze im Innern von Zellen Linnaea 16:278. 1842. "Naegeli. Ernahrungsmechanismus der niederen Organismen. Sitzber. d. Munch. Akad. July, 1879. uNaegeli. Ernahrung der niederer Pilze durch Kohlen und Stickstoffverbindungen. Bot. Mittheil. 3 : 395. 1881. "Nathusius. Symbiose der Waldbiiume mit Mycorhiza. Zeit- schr. f. Naturw. 62:Hft. 6 1890. '-Nicolai. Das Wachstum der Wurzel. Schr. d. phys.-Okon. Ges. z. Koenigsberg. 7 : 35, 78. 1875. 210 MINNESOTA BOTANICAL STUDIES. Noack F. Ueber Micorhizende-bildende Pilze. Bot. Ztg. 47:389. 1889. Nobbe F. Vegetationsversuche in Boden mit lokalisirten Nathrstoffen. Landw. Ver. Sta. 6:98. 1868. iNobbe F. Ueber die Stickstoffernahrung der Leguminosen. Verhandl. d. Ges. Deut. Naturf. nnd Aerzte. Ver- samml z. Bremen, 2:551. 1890. -Nobbe F. Stiekstoffernabrung der Leguminosen. Chem. Cen- tralb. 1: No. 6. 1891. i Nobbe, Schmid^ Hiltner and Hotter. Versuche ueber die Stick- stoff assimilation der Leguminosen. Landw. Yer. Sta. 39:327. 1891 Nobbe, Schmid^ Hiltner and Hotter. Ueber die physiologische Bedeutung den WurzelknGllchen von Eleagnus angus- tifolius. Landw. Ver. Sta. 41 : 138. 1892. INobbe^ Schmid, Hiltner and Hotter. Ueber die Verbreitungs- ^ fahigkeit der Leguminosen Bacterien im Boden. Landw. Ver. Sta. 41:137. 1892. Nobbe and Hiltner. “The interchange between leguminous plants and the bacteria causing root tubercles.” Sachss. Landw. Zeitschr. 165. 1893. ^Oliver F. W. On Sarcodes sanguinea. Ann. Bot. 4:303. 1890. -Otto R. Die Assimalation des freien atmospharischen Stick- stoffes durch die Pflanze. Bot. Centralb. 46:387. 1890. Also, 47:62, 123, 175. 1891. Otto. See Prank. dPenzig 0. Die Krankheit der Edelkastanien und B. Frank’s Mykorhiza. Ber. d. deut. Bot. Ges. 3 : 301. 1885. ^Persoon. Traite sur les champignons comestibles. 1818. Petermann A. “Contribution a la question de l’azote.” Mem. d. 1’ Acad. Roy. d. Belg. 1891. Petermann A. Beitrage zur Stickstoffrage. Abstract. Chem. Centralb. 1:988. 1893. Ibid. 2:889. 1892. Ibid. 3: No. 20. 1892. -Petermann A. Contribution a la question de l’azote. Mem. d. T Acad. roy. d. Belg. 47. 1892.