1. ADDOMS, R. M. The effect of the hydrogen ion on the protoplasm of the root hairs of wheat. Am. Jour. Bot., 10:211-220. 1923.

   2. ALBRECHT, W. A. Nitrate accumulation under straw mulch, Soil Science, 14:299-305. 1922.

   3. ALLEN, R. W. Condition of root system of apple trees in the Hood River district. Ore. Agr. Exp. Sta. Rept. of the Hood River Branch Exp. Sta. for 1914-1915, pp. 20-24.

   4. ALLISON, R. V., and SHIVE, J. W. Studies on the relation of aeration and continuous renewal of nutrient solution to the growth of soybeans in artificial culture. Am. Jour. Bot., 10:554-566. 1923.

   5. ALWAY, F. J., McDOLE, G. R., and ROST, C. O. The loess soils of the Nebraska portion of the transition region: VI, the relative "rawness" of the subsoils. Soil Science, 3:9-36. 1917.

   6. ALWAY, F. J., et al. Relation of minimum moisture content of subsoil of prairies to hygroscopic coefficient. Bot. Gaz., 67:185-207. 1919.

   7. ANDERSON, M. L. Soil conditions affecting the prevalence of Fomes annosus (Trametes radiciperda). Trans. Boy. Scottish Arbor. Soc. 35:112-117. 1921.

   8. AUSTIN, C. L. Influence of pruning upon top and root development. Cal. Agr. Exp. Sta. Rept., 1923:210. 1923.

   9. BAKER, O. E. The agriculture of the Great Plains region. Ann. Assoc. Am. Geog., 13:109-167. 1923.

   10. BALLANTYNE, A. B. Fruit tree root systems, spread and depth as partly determined by excavations on the southern experiment farm. St. George, Utah. Utah Agr. Exp. Sta., Bull. 143. 1916.

   11. BALLS, W. L. The cotton plant in Egypt. Macmillan & Co., London. 1919.

   12. BARKER, B. T. P. Studies on root development. Univ. Bristol Ann. Rept. Agric. and Hort. Res. Sta., 1921:9-20. 1921.

   13. BATES, C. G. Windbreaks: their influence and value. U. S. Forest Service, Bull. 86. 1911.

   14. BECKWITH, M. H. Report of the assistant horticulturist. N. Y. Agr. Exp. Sta. Rept., 4:261-267. 1886.

   15. BEESON, M. A., and MURPHY, H. F. The effect of lime and organic matter on the so-called hardpan subsoils. Okla. Agr. Exp. Sta., Bull. 143. 1922.

   16. BERGMAN, H. F. The relation of aeration to the growth and activity of roots and its influence on the ecosis of plants in swamps. Ann. Bot., 34:13-33. 1920.

   16a. BLINN, P. K. Alfalfa, the relation of type to hardiness. Col. Agr. Exp. Sta., Bull. 181:3-16. 1911.

   17. BREASEALE, J. F. The injurious after-effects of sorghum. Jour. Am. Soc. Agron., 16:689-700.1924.

   18. BRENCHLEY, W. E. Some factors in plant competition. Ann. Appl. Biol., 6:142-170. 1919.

   19. BRENCHLEY, W. E., and JACKSON, V. G. Root development in barley and wheat under different conditions of growth. Ann. Bot., 35:533-556. 1921.

   20. BRENCHLEY, W. E., and SINGH, K. Effect of high root temperature and excessive insolation upon growth. Ann. Appl. Biol., 9:197-209. 1922.

   21. BRIERLEY, W. B. The occurrence of fungi in the soil, in RUSSELL et al, The Micro-organisms of the Soil, pp. 119-120. 1923.

   22. BRIGGS, L. J., and BELZ, J. O. Dry farming in relation to rainfall and evaporation. U. S. Dept. Agr., Bur. Plant Ind., Bull. 188. 1911.

   23. BRIGGS, L. J., and SHANTZ, H. L. Relative water requirements of plants. Jour. Agr. Res., 3:1-64. 1914.

   24. BRIZI, U. Ricerche sulla malattia del rise detta "brusone." Ann. Istit. Agr. Ponti., 5:79-95. 1905.

   25. BRIM, U. Ulteriori ricerche intorno al brusone del rise. Ann. Istit. Agr. Ponti., 6:61-103. 1906.

   26. BROWN, P. E. A study of bacteria at different depths in some typical Iowa soils. Centrbl. f. Bakt., II, 37:497-521. 1913.

   27. BROWN, P. E., and STALLINGS, J. H. Inoculated legumes as nitrogenous fertilizers. Soil Science, 12:365-407. 1921.

   28. CALL, L. E. The effect of different methods of preparing a seed bed for winter wheat upon yield, soil moisture, and nitrates. Jour. Am. Soc. Agron., 6:249-259. 1914.

   29. CANNON, W. A. The root habits of desert plants. Carnegie Inst. Wash. Pub. 131. 1911.

   30. CANNON, W. A. A note on a chaparral-forest relation at Carmel, Cal. Plant World, 16:36-38. 1913.

   31. CANNON, W. A. On the relation of root growth and development to the temperature and aeration of the soil. Am. Jour. Bot., 2:211-224. 1915.

   32. CANNON, W. A. On the relation between the rate of root-growth and the oxygen of the soil. Carnegie Inst. Wash. Year Book, 15:74-75. 1917.

   33. CANNON, W. A. Soil temperature and plant growth. Plant World, 20:361-363. 1917.

   34. CANNON, W. A. Relation of the rate of root-growth in seedlings of Prosopis velutina to the temperature of the soil. Carnegie Inst. Wash. Year Book, 16:82. 1918.

   35. CANNON, W. A. Root-growth of Prosopis velutina and Opuntia versicolor under conditions of a small oxygen supply in the soil. Carnegie Inst. Wash. Year Book, 16:82-83. 1918.

   36. CANNON, W. A. Effect of a diminished oxygen-supply in the soil on the rate of the growth of roots. Carnegie Inst. Wash. Year Book, 19:59-61. 1921.

   37. CANNON, W. A. The influence of the temperature of the soil on the relation of roots to oxygen. Science, n. s., 68:331-332. 1923.

   38. CANNON, W. A. A note on the relation of root growth in the soil to oxygen supply: the growth ratio. Ecology, 5:319-321.1924.

   38a. CANNON, W. A. Physiological features of roots, with especial reference to the relation of roots to aeration of the soil, with a chapter on differences between nitrogen and helium as inert gases in anaerobic experiments on plants by E. E. Free. Carnegie Inst. Wash. Pub. 368: 1-168. 1925.

   39. CANNON, W. A., and FREE, E. E. The ecological significance of soil aeration. Science, n..s., 45:178-180. 1917.

   39a. CARLSON, F. A. The effect of soil structure on the character of alfalfa root- systems. Jour. Amer. Soc. Agron., 17: 336-345. 1925.

   40. CHILCOTT, E. C., and COLE, J. S. Subsoiling, deep tilling, and soil dynamiting in the Great Plains. Jour. Agr. Res., 14:481-521. 1918.

   41. CHURCHILL, O. O., and WRIGHT, A. H. The grain sorghums. Okla. Agr. Exp. Sta., Bull. 102. 1914.

   42. CLAYTON, E. E . The relation of temperature to the Fusarium wilt of the tomato. Am. Jour. Bot., 10:71-88. 1923.

   43. CLEMENTS, F. E. Plant indicators, the relation of plant communities to process and practice. Carnegie Inst. Wash. Pub. 290. 1920.

   44. CLEMENTS, F. E. Aeration and air-content, the rôle of oxygen in root activity. Carnegie Inst. Wash. Pub. 315. 1921.

   45. CLEMENTS, F. E., and WEAVER, J. E. Experimental vegetation, the relation of climaxes to climates. Carnegie Inst. Wash. Pub. 355. 1924.

   46. COLBY, A. S. Preliminary report of the root systems of grape varieties. Proc. Am. Soc. Hort. Sci., 19:191-194. 1922.

   47. COLLINS, G. N. A drought-resisting adaptation in seedlings of Hopi maize. Jour. Agr. Res., 1:293-302. 1914.

   48. COVILLE, F. V. Experiments in blueberry culture. U. S. Dept. Agr. Bur. Plant Ind., Bull. 193. 1910.

   49. CRIST, J. W., and WEAVER, J. E. Absorption of nutrients from subsoil in relation to crop yield. Bot. Gaz., 77:121-148. 1924.

   50. CULLINAN, F. P. Root development of the apple as affected by cultural practices. Proc. Am. Soc. Hort. Sci., 1921:197-203. 1922.

   51. CUTLER, D. W. Protozoa of the soil, in RUSSELL et al. The microorganisms of the soil. Long mans, Green & Co., London. 1923.

   52. DARWIN, C. Vegetable Mould and Earthworms. D. Appleton & Co., New York. 1881.

   53. DAVIS, B. M. Root-development of lucerne. New Zealand Jour. Agr., 28:179-180. 1924.

   54. DEAN, D. Sub-surface application of potato fertilizers. Proc. Potato Assoc. Am. for 1923, 10:110-113. 1924.

   55. DICKSON, J. G., et al. The nature of resistance to seedling blight of cereals. Proc. Nat. Acad. Sci., 9:434-439. 1923.

   56. DICKSON, J. G. Influence of soil temperature and moisture on the development of the seedling blight of wheat and corn caused by Giberrela saubinetii. Jour. Agr. Res., 23: 837-870. 1923.

   57. ELLIOTT, G. R. B. Relation between the downward penetration of corn roots and water level in peat soil. Ecology, 5:175-178. 1924.

   58. EMERSON, F.W. Subterranean organs of bog plants. Bot. Gaz., 72:359-374. 1921.

   59. FINCH, V. C., and BAKER, O. E. Geography of the world's agriculture. U.S. Dept. Agr. 1917.

   60. FRANK, B. Die Assimilation des freien Stickstoffs durch die Pflanzenwelt. Bot. Ztg., 51:139-156. 1893.

   61. GARCIA, F. Sweet potato culture. N. M. Agr. Exp. Sta., Bull. 70. 1909.

   62. GARDNER, V. R., BRADFORD, F. C., and HOOKER, H. D. The Fundamentals of Fruit Production. p. 19. McGraw-Hill Book Company, Inc., New York. 1922.

   63. Ibid., 587.

   64. GARNER, W. W., and ALLARD, H. A. Further studies in photoperiodism, the response of the plant to relative length of day and night. Jour. Agr. Res., 23:871-920. 1923.

   64a. GARNER, W. W., LUNN, W. M., and BROWN, D. E. Effects of crops on the yields of succeeding crops in the rotation, with special reference to tobacco. Journ. Agr. Res., 30:1095-1132. 1925.

   65. GARVER, S. Alfalfa root studies. U. S. Dept. Agr., Bull. 1087. 1922.

   66. GERICKE, W. F. Differences effected in the protein content of grain by applications of nitrogen made at different growing periods of the plants. Soil Science, 14:103-109. 1922.

   67. GERICKE, W. F. Certain relations between root development and tillering in wheat: significance in the production of high-protein wheat. Am. Jour. Bot., 9:366-369. 1922.

   68. GERICKE, W. F. Investigations of physiological processes related to root systems of plants. Cal. Agr, Exp. Sta. Rept., 1922:116-117. 1922.

   69. GILE, P. L., and CARRERO, J. O. Absorption of nutrients as affected by the number of roots supplied with the nutrient. Jour. Agr. Res., 9:73-95. 1917.

   70. GILMAN, J. C. Cabbage yellows and the relation of temperature to its occurrence. Ann. Mo. Bot. Gar., 3:25-84. 1916.

   71. GOFF , E. S. A study of the roots of certain perennial plants. Wis. Agr. Exp. Sta. Rept., 114:286-298. 1897.

   72. GOFF, E. S. The resumption of root growth in spring. Wis. Agr. Exp. Sta. Rept., 15:220-228. 1898.

   73. HAASIS, F. W. Relations between soil type and root form of western yellow pine seedlings. Ecology, 2:292-303. 1921.

   74. HABERLANDT, F. Die oberen und unteren Temperaturgrenzen für die Keimung der wicktigeren landw. Sämereien. Landw. Versuchs-stationen, 17:104-116. 1874.

   75. HARLAN, H. V., and ANTHONY, S. Effect of time of irrigation on kernel development of barley. Jour. Agr. Res., 21:29-45. 1921.

   76. HARRIS, F. S. The effect of soil moisture, plant food, and age on the ratio of tops to roots in plants. Jour. Am. Soc. Agron., 6:65-75. 1914.

   77. HARRIS, F. S. The irrigation of sugar beets. Utah Agr. Exp. Sta., Bull. 156. 1917.

   78. HARRIS, F. S. Soil Alkali, its Origin, Nature, and Treatment. John Wiley & Sons, New York. 1920.

   79. HAYS, W. M. Clovers, Fifth biennial report, Board of Regents of University of Minnesota, suppl. Dept. Agr. 1888.

   80. HAYS, W. M. Corn, its habits of root growth, methods of planting and cultivating, notes oil ears and stools or suckers. Minn. Agr. Exp. Sta., Bull. 5:5-33. 1889.

   81. HAYS, W. M. Roots of crops. N. D. Agr. Exp. Sta., Bull. 10:47-49. 1893.

   82. HAYS, W. M., and BOSS, A. Wheat: varieties, breeding, cultivation. Minn. Agr. Exp. Sta., Bull. 62. 1899.

   83. HAYES, H. K., and GARBER, R. J. Breeding crop plants. 250. McGraw-Hill Book Company, Inc., New York. 1921.

   84. HEADDEN, W. P. Alfalfa. Colo. Agr. Exp. Sta., Bull. 35. 1896.

   85. HEINICKE, A, J. Some relations between circumference and weight and between root and top growth of young apple trees. Proc. Am. Hort. Sci. for 1921, 18:222-227. 1922.

   86. HELM, C. A. Corn in Missouri. Mo. Agr. Exp. Sta., Bull. 185. 1921.

   87. HICKMAN, J. C. Root development of corn. Director's Rept., Penn. State Col. for 1887, 2:90-103.

   88. HILGARD E. W. A report on the relations of soil to climate. U. S. Dept. Agr. Weather Bur., Bull. 3. 1892.

   89. HILGARD, E. W. Soils, 6th ed., pp. 168-171, 245. The Macmillan Co., New York. 1914.

   90. HOAGLAND, D. R. The freezing-point method as an index of variations in the soil solution due to season and crop growth. Jour. Agr. Res., 12:369-395. 1918.

   91. HOAGLAND, D. R., and MARTIN, J. C. Effect of season and crop growth on the physical state of the soil. Jour. Agr. Res., 20:397-404. 1920.

   92. HOFFER, G. N., and CARR, R. IT. Accumulation of aluminium and iron compounds in corn plants and its probable relation to root-rots. Jour. Agr. Res., 23:801-823. 1923.

   93. HOFFER, G. N., and TROST, J. F. The accumulation of iron and aluminium compounds in corn plants and its probable relation to root-rots, II. Jour. Am. Soc. Agron., 15:323-331. 1923.

   94. HOLBERT, J. R., and KOEHLER, B. Anchorage and extent of corn root systems. Jour. Agr. Res., 27:71-78. 1924.

   95. HOLBERT, J. R., et al. Corn root, stalk, and ear rot diseases, and their control thru seed selection and breeding. Ill. Agr. Exp. Sta., Bull. 255. 1924.

   96. HORTON, R. E. Rainfall interception. Monthly Weather Review, 47-603-623. 1919.

   97. HOWARD, A. Recent investigations on soil-aeration, part I, with special reference to agriculture. Agr. Jour. India, 13:416-429. 1918.

   98. HOWARD, A. The influence of soil factors on disease resistance. Ann. Appl. Biol., 7:373-389. 1921.

   99. HOWARD, A. The effect of grass on trees. Proc. Royal Soc. B., 97:284-320. 1925.

   100. HOWARD, A., and HOWARD, G. L. C. The economic significance of the root development of agricultural crops. Agr. Jour. India, Indian Sci. Congr. Number. 1917.

   101. HOWARD, A., and HOWARD, G. L. C. Some aspects of the indigo industry in Bihar. Mem. Dept. Agr. India, 11:1-36. 1920.

   101a. HOWARD, A. Disease in plants. Agr. Jour. India, 16:626-637. 1921.

   102. HOWE, C. G. Pectic material in root hairs. Bot. Gaz., 72:313-320. 1921.

   103. IMMS, A. D. The invertebrate fauna of the soil (other than protozoa), in Russell, et al, The microorganisms of the soil. Longmans, Green & Co., London. 1923.

   104. JEAN, F. C., and WEAVER, J. E. Root behavior and crop yield under irrigation. Carnegie Inst. Wash. Pub, 357. 1924.

   105. JEAN, F. C. Unpublished data, department of botany, University of Nebraska. 1925.

   105a. JEFFS, R. E. The elongation of root hairs as affected by light and temperature. Amer. Jour. Bot., 12:577-606. 1925.

   106. JENSEN, C. A. Relation of inorganic soil colloids to plowsole in citrus groves in southern California. Jour. Agr. Res., 15:505-519. 1918.

   107. JOHNSON, J. Fusarium-wilt of tobacco. Jour. Agr. Res., 20:515-536. 1921.

   108. JOHNSON, J., and HARTMAN, R. E. Influence of soil environment on the root-rot of tobacco. Jour. Agr. Res., 17:41-86. 1919.

   109. JOHNSON, J., and MILTON, R. IT. Strains of white Burley tobacco resistant to root-rot. U. S. Dept. Agr., Bull. 765. 1919.

   110. JONES, L. R. Soil temperature as a factor in phytopathology. Plant World, 20:229-237. 1917.

   111. JONES, L. R. The relation of environment to disease in plants. Am. Jour. Bot., 11:601-609. 1924.

   112. JONES, L. R., et al. Fusarium resistant cabbage. Wis. Agr. Exp. Sta., Research Bull. 48. 1920.

   113. JONES, L. R., and GILMAN, J. C. The control of cabbage yellows through disease resistance. Wis. Agr. Exp. Sta., Research Bull. 38. 1915.

   114. JONES, L. R., and TISDALE, W. B. Effect of soil temperature upon the development of nodules on the roots of certain legumes. Jour. Agr. Res., 22:17-31. 1921.

   115. JONES, L. R., and TISDALE, W. B. The influence of soil temperature upon the development of flax wilt. Phytopathology, 12:409-413. 1922.

   116. KEARNEY, T. H., et al. Indicator significance of vegetation in Tooele Valley, Utah. Jour. Agr. Res., 1:365-418. 1914.

   117. KELLEY, W. P., and THOMAS, E. E. The effects of alkali on citrus trees. Cal. Agr. Expt. Sta., Bull. 318. 1920.

   118. KIESSELBACH, T. A. Transpiration as a factor in crop production. Nebr. Agr. Exp. Sta., Research Bull. 6:1-214. 1916.

   119. KIESSELBACH, T. A. Studies concerning the elimination of experimental error in comparative crop tests. Nebr. Agr. Exp. Sta., Research Bull. 13. 1917.

   120. KING, C. J. Water-stress behavior of Pima Cotton in Arizona. U. S. Dept. Agr., Bull. 1018.1922.

   121. KING, F. H. Natural distribution of roots in field soils. Wis. Agr. Exp. Sta. Rept., 1892:112; also 1893:160.

   122. KING, F. H. Observations and experiments on the fluctuations in the level and rate of movement of ground-water on the experiment station farm and at Whitewater, Wis. Rept. Wis. Agr. Exp. Sta., 9:129-218. 1893.

   123. KING, F. H. The natural distribution of roots in fields soils. Wis. Agr. Exp. Sta. Rept. for 1893, 10:160-164. 1894.

   124. KNAPP, G. S. Relation of crop yields to quantity of irrigation water in Southwestern Kansas. Kan. Agr. Exp. Sta., Bull. 228. 1922.

   125. KUNKEL, L. O. Tissue invasion by Plasmodiophora brassicae. Jour. Agr. Res., 14:543-572. 1918.

   126. LATSHAW, W. L., and MILLER, E. C. Elemental composition of the corn plant. Jour. Agr. Res., 27:845-860. 1924.

   127. LATTA, W. C. Field experiments with corn. Ind. Agr. Exp. Sta., Bull. 39:35. 1892.

   128. LEES, R. D. Root development in wheat. Agr. Gaz. New South Wales, 35:609-612. 1924.

   129. LIVINGSTON, B. E., and FREE, E. E. The effect of deficient soil oxygen on the roots of higher plants. The Johns Hopkins Univ., Circ. 1917:380. 1917.

   130. LOCKE, L. F., and CLARK, J. A. Normal development. of wheat plants from seminal roots. Jour. Am. Soc. Agron., 16:261-268. 1924.

   131. LYON, T. L., and BUCKMAN, H. O. The nature and properties of soils. A college text of edaphology, p. 282. The Macmillan Co., New York. 1923.

   132. MARBUT, C. F. Soils of the Great Plains. Ann. Assoc. Am. Geog., 13:41-66. 1923.

   133. MASCHHAUPT, J. G. De beworteling onzer cultuurgewassen. [Root systems of agricultural plants.] Verslag. Landbouwk. Onderzoek. Rijkslandbouwproefstat. (Netherlands), 16:76-89. 1915. (Abs. in Exp. Sta. Rec., 31:733. 1914).

   134. MAXIMOW, N. A., and LEBEDINCEV, ELISABETH. Über den Einfluss von Beleuchtungsverhiiltnissen auf die Entwickelung des Wurzelsystems. Ber. Deutsch. Bot. Ges., 41:292-297. 1923.

   135. McBETH, I. G. Relation of the transformation and distribution of soil nitrogen to the nutrition of citrus plants. Jour. Agr. Res., 9:183-252. 1917.

   136. McDOUGALL, W. B. Thick-walled root hairs of Gleditsia and related genera. Am. Jour. Bot., 8:171-175. 1921.

   137. MEGEE, C. R. Unpublished data, department of farm crops, Michigan Agricultural College.

   138. MILLAR, C. E. Hill fertilization of corn. Mich. Agr. Exp. Sta., Quart. Bull. 5:69-73. 1922.

   139. MILLAR, C. E. Availability of nutrients in subsoils. Soil Science, 19:275-285. 1925.

   139a. MILLAR, C. E. The feeding power of plants in different soil horizons. Jour. Amer. Soc. Agron., 17:150-156.1925.

   140. MILLER, E. C. Comparative study of the root systems and leaf areas of corn and the sorghums. Jour. Agr. Res., 6:311-332. 1916.

   141. MILLER, M. F. The soil and its management. Ginn & Co., Chicago. 1924,

   142. MOSIER, J. G., and GUSTAFSON, A. F. Soil moisture and tillage for corn. Ill. Agr. Exp. Sta., Bull. 181. 1915.

   143. MURRAY, T. J. The effect of straw on the biological soil processes. Soil Science, 12:233-259. 1921.

   144. MUSGRAVE, G. W. Agronomist, N. J. Agr. Exp. Sta., Correspondence. 1924.

   145. NELSON, N. T. The effects of frequent cutting on the production, root reserves, and behavior of alfalfa. Jour. Am. Soc. Agron., 17:100-113. 1925.

   146. NOBBE, F. Ueber die feinere Verästelung der Pflanzenwurzeln. Landw. Vers. Stat., 4:212-224. 1862.

   147. NOBBE, F. Die Pflanzencultur in Wasser, und ihre Bedeutung für die Landwirtschaft, Landw. Vers. Stats., 11:391-397. 1809.

   148. NOYES, H. A., TROST, J. F., and YODER, L. Root variations induced by carbon dioxide gas additions to soil. Bot. Gaz., 66:364-373. 1918.

   149. NOYES, H. A., and WEGHORST, T. H. Residual effects of carbon dioxide gas additions to soil on roots of Lactuca sativa. Bot. Gaz., 69:332-336. 1920.

   150. OSVALD, H. Untersuchungen über die Einwirkung des Grundwasserstands auf die Bewurzelung von Wiesenpflanzen auf Moorboden. Fühling's Landw. Zeit., 68:321, 370. 1919.

   150a. PACK, D.A. Time of year to plant mother beets for seed production. Jour. Agr. Res., 30: 811-818. 1925.

   151. PALLADIN, V. I. Plant physiology. Edited by B. E. Livingston, p. 82. P. Blakiston's Son & Co., Philadelphia. 1923.

   152. PELTIER, G. L., and KING, C. J. Ozonium root rot, unpublished data.

   153. PIPER, C. V. Plants and plant culture. Science, n. s., 53:269-279. 1921.

   154. PRIESTLY, J. H., and NORTH,. E. E. Physiological studies in plant anatomy: Ill, The structure of the endodermis in relation to its function. New Phytologist, 21:113-139. 1922.

   155. PULLING, H. E. Root habit and plant distribution in the far north. Plant World, 21:223-233. 1918.

   156. RIED, MARY E. Quantitative relations of carbohydrates to nitrogen in determining growth responses in tomato cuttings. Bot. Gaz., 77:404-418. 1924.

   157. REID, MARY E. The influence of nitrogen content of seeds upon the proportions of shoots to roots in seedlings, abstract of paper read before Am. Soc. Plant Physiologists and Physiological Section of Bot. Soc. Am., Dec. 29, 1924.

   158. RICHARDS, E. H. Dissolved oxygen in rain-water. Jour. Agr. Sci., 8:331-337. 1917.

   159. ROBBINS, W. W. The botany of crop plants. 2d ed., p. 22. P. Blakiston's Son & Co., Philadelphia. 1924.

   160. Ibid. p. 91.

   161. ROBERTS, E. A. The epidermal cells of roots. Bot. Gaz., 62:488-506. 1916.

   162. Root washings, Rept. N. Y. Agr. Exp. Sta. for 1884. 3:305- 315. 1885.

   163. ROTMISTROV, V. Root-system of cultivated plants of one year's growth. Odessa. 1909.

   164. ROTMISTROV, V. G. The nature of drought according to the evidence of the Odessa Experiment Field. Odessa. 1913.

   165. RUSSEL, J. C. Unpublished data, department of agronomy, University of Nebraska.

   166. RUSSELL, E. J., et al. The micro-organisms of the soil. p. v. Longmans, Green & Co., London. 1923.

   167. RUSSELL, E. J. The development of the idea of a soil population. pp. 16-17, in RUSSELL et al, The micro-organisms of the soil. 1923.

   168. RUSSELL, E. J. Soil conditions and plant growth. p. 39. Longmans, Green & Co., London. 1917.

   169. Ibid. p. 56.

   170. RUSSELL, E. J. Soil conditions and plant growth. 4th ed. 1921.

   171. RUSSELL, E. J., and APPLEYARD, A. The atmosphere of the soil: its composition and the causes of variation. Jour. Agr. Sci., 7:1-48. 1915.

   172. SACHS, J. Handbuch der Experimental-Physialogie der Pflanzen. p. 177. 1865.

   173. SAHUT, F. De l'influence directe du sujec Sur le greffon. Rev. Hort., 57:305- 309. 1885.

   174. SALISBURY, E. J. The soils of Blakeney point: a study of soil reaction and succession in relation to the plant covering. Ann. Bot., 36:391-431. 1922.

   175. SAMPSON, A. W. Range and pasture management. p. 156. John Wiley & Sons, New York. 1923.

   176. SANBORN, J. W. Roots of farm crops. Utah Agr. Exp. Sta., Bull. 32. 1894.

   177. SANDSTEN, E. P. Potato culture in Colorado. Colo. Agr. Exp. Sta., Bull. 243. 1918.

   178. SCHULZE, B. Wurzelatlas. Berlin, vol. 1, 1911; vol. 2, 1914.

   179. SCHULZE, B. Studien über die Bewurzelung unserer Kulturpflanzen. Festschrift 50, Jubildäum Agr. Chem. Versuchs- u. Kontrollstat., Breslau, pp. 67- 95. 1906. (Abs. in Exp. Sta. Rec., 31:733. 1914.)

   180. SCHWARZ, F. Die Wurzelharre der Pflanzen. Untersuch. Bot. Instit. Tübingen, 1:135-189. 1883.

   181. SCOTT, H. The influence of wheat straw on the accumulation of nitrates in the soil. Jour. Am. Soc. Agron., 13:233-258. 1921.

   182. SEWELL, M. C. Effect of Andropogon sorghum on succeeding crops of Triticum sativum vulgare. Bot. Gaz., 75:1-26. 1923.

   183. SHANTZ, H. L. Natural vegetation as an indicator of the capabilities of land for crop production in the Great Plains area. U. S. Dept. Agr., Bur. Plant Ind., Bull. 201.1911.

   184. SHANTZ, H. L. The natural vegetation of the Great Plains region. Ann. Assoc. Am. Geog., 13:81-107. 1923.

   185. SHANTZ, H. L. Natural vegetation, grassland and desert shrub. U. S. Dept. Agr., Atlas of American Agriculture,. Section E. 1924.

   186. SHEPPERD, J. H. Root systems of field crops. N. D. Agr. Exp. Sta., Bull. 64. 1905.

   187. SIFGLINER, J. B. Temporary roots of the sorghums. Jour. Am. Soc. Agron., 12:143-145. 1920.

   188. SIEVERS, F. J., and HOLTZ, H. F. The silt loam soils of eastern Washington and their management. Wash. Agr. Exp. Sta., Bull. 166. 1922.

   189. SKENE, M. The biology of flowering plants. pp. 5-6. Sidgwick & Jackson, London. 1924.

   190. SMITH, J. W. Agricultural meteorology, the effect of weather on crops. p. 79. The Macmillan Co., New York. 1920.

   191. SNOW, L. M. The development of root hairs. Bot. Gaz., 40:12-48. 1905.

   192. SORAUER, P. Manual of plant diseases. 3d ed., translated by F. Dorrance, 1:841. 1920.

   193. SOUTHWORTH, W. A study of the influence of the root system in promoting hardiness in alfalfa. Sci. Agric. (Canada), 1:5-9. 1921.

   194. SPILLMAN, W. J. Farm grasses of the United States. Orange Judd Co., New York. 1907.

   195. STEWART, GEORGE. Potato production. Utah Ag'r. Exp. Sta., Circ. 40. 1919.

   196. STOKLASA, J., and ERNEST, A. Beiträge zur Lösung der Frage der chemischen Natur des Wurzelsekretes. Jahrb. Wiss. Bot., 46:55-102. 1908.

   197. Storrs Agr. Exp. Sta., Bull. 3. 1889.

   198. STUART, W. Production of late or main-crop potatoes. Farmers' Bull. U. S. Dept. Agr., 1064. 1919.

   199. SWEZEY, G. D. Soil temperatures at Lincoln, Nebr. 1888-1902, Nebr. Agr. Exp. Sta., Ann. Rept., 16:95-129. 1903.

   200. TACKE, BR. Die Entwicklung der Wurzeln und der Kalkgehalt des Bodens. Fühling's Landw. Zeitg., 69:58-59. 1920.

   201. TAUBENHAUS, J. J., and KiLLOUGH, D. T. Texas root rot of cotton and methods of its control. Tex. Agr. Exp. Sta., Bull. 307. 1923.

   202. TEN EYCK, A. M. Roots of plants. N. D. Agr. Exp. Sta., Bull. 36. 1899.

   203. TEN EYCK, A. M. A study of the root systems of cultivated plants grown as farm crops. N. D. Agr. Exp. Sta., Bull. 43. 1900.

   204. TEN EYCK, A. M. The roots of plants. Kan. Agr. Exp. Sta., Bull, 127. 1905.

   205. The influence of the depth of tillage upon the depth of roots. N. Y.. Exp. Sta. Rept., 1888: 171-173. 1889.

   206. THOMPSON, C. A., and BARROWS, E. L. Soil moisture movement in relation to growth of alfalfa. N. M. Agr. Exp. Sta., Bull. 123. 1920.

   207. TISDALE, W. H. Flaxwilt: a study of the nature and inheritance of wilt resistance. Jour. Agr. Res., 11:573-605. 1917.

   208. TISDALE, W. H. Relation of temperature to the growth and infecting power of Fusarium. lini. Phytopathology, 7:356-360. 1917.

   209. TROMMER, M. Untersuchungen über den Einfluss der mechanischen Bodenbeschaffenheit auf das Wachstum der Wurzeln. Landw. Jahrb. Bayern, 10:163-219. 1920. (Abs. in Exp. Sta. Rec., 48:513-514, 1923.)

   210. TRUOG, EMIL. Soil acidity: I, Its relation to the growth of plants. Soil Science, 5:169-195. 1918.

   211. TURNER, H. C. The effect of planting method upon growth of western yellow pine. Jour. Fores., 16:399-403. 1918.

   212. Viticultural nursery, Wahgunyah, visit of inspection. Victoria Jour. Dept. Agr., 14:345-353. 1916.

   213. VOROB'EV, S. I. On the study of the root systems of cereals and forage plants. Selsk. Khoz. Liesov., 251:477. 1916.

   214. WAKSMAN, S. A. Influence of microorganisms upon the carbon-nitrogen ratio in the soil. Jour. Agr. Sci., 14:555-562. 1924.

   215. WALKER, J. C., and JONES, L. R. Relation of soil temperature and other factors to onion smut infection. Jour. Agr. Res., 22:235-262. 1921.

   216. WATERS, H. J. Field experiments with corn. Mo. Agr. Exp. Sta., Bull. 14:19. 1891.

   217. WATT, R. D. The influence of phosphatic fertilizers on root development. Rept. Austral. Assoc. Adv. Sci., 1913, 14:661-665. 1914. (Abs. in Exp. Sta. Rec., 33:526. 1915.)

   218. WEAVER, J. E. A study of the root-systems of prairie plants of southeastern Washington. Plant World, 18:227-248; 273-292. 1915.

   219. WEAVER, J. E. A study of the vegetation of southeastern Washington and adjacent Idaho. Nebr. Univ. Studies, 17:1-133. 1917.

   220. WEAVER, J. E. The ecological relations of roots. Carnegie Inst. Wash. Pub. 286. 1919.

   221. WEAVER, J. E. Root development in the grassland formation, a correlation of the root systems of native vegetation and crop plants. Carnegie Inst. Wash. Pub. 292. 1920.

   222. WEAVER, J. E. Plant production as a measure of environment, a study in crop ecology. Jour. Ecology, 12:205-237. 1924.

   223. WEAVER, J. E. Investigations on the root habits of plants. Am. Jour. Bot., 12:502-509. 1925.

   224. WEAVER, J. E., and CRIST, J. W. Relation of hardpan to root penetration in the Great Plains. Ecology, 3:237-249. 1922.

   225. WEAVER, J. E., JEAN, F. C., and CRIST, J. W. Development and activities of, roots of crop plants, a study in crop ecology. Carnegie Inst. Wash. Pub. 316. 1922.

   226. WEAVER, J. E., KRAMER, JOSEPH, and REED, MAUD. Development of root and shoot of winter wheat under field environment. Ecology, 5:26-50. 1924.

   227. WHERRY, E. T. Soil acidity and a field method for its. measurement. Ecology, 1:160-173.1920.

   228. WHITAKER, E. S. Root hairs and secondary thickening in the Compositae, Bot. Gaz., 76:30-58. 1923.

   229. WILLARD, C. J., and THATCHER, L. E. Experiments with Hubam clover. Ohio Agr. Sta., Monthly Bull., 7:3-18. 1922.

   230. WILLIAMS, C. G., and WELTON, F. A. Corn experiments. Ohio Agr. Exp. Sta., Bull. 282. 1915.

   231. WINKLER, E. A. Hubam as a farm crop. Gleanings in Bee Culture, 50:762- 764. 1922.

   232. ZEDFRBAUER, E. Ein Beitrag zur Kenntnis des Wurzelwachstums der Fichte. Centralbl. gesam. Forstw., 46:336-337. 1920. (Abs. in Bot. Abst., 13:1166, no. 7669. 1924.)