1917] AGKIOULTUKAL BOTANY. 325 



intact, it was found that the production of shoots is in proportion to the mass 

 of the leaves themselves. The investigation here reported leads to the assump- 

 tion that the growth of dormant buds is determined by and is in proportion to 

 the quantity of a certain material available for the buds. The author does not 

 discuss the nature of the substances which cause the growth of buds, but he 

 points out the fact that leaves form no shoots or very few if kept in the dark. 

 This is believed to indicate that the material from which the new shoots are 

 produced in a leaf is itself to a large extent a direct product of or is dependent 

 upon the assimilatory activity of the leaf. 



Influence of the leaf upon root formation and geotropic curvature in the 

 stem of Bryophyllum calycinum and the possibility of a hormone theory of 

 these processes, J. Loeb (Bot. Gaz., 63 {1911), No. 1, pp. 25-50, figs. SO).— In 

 studies previously noted (E. S. R., 37, p. 127), which showed that substances 

 (water or solutes) may be drawn away from the leaves to accelerate organ 

 formation in the stem but that if not so removed, they will accelerate root and 

 shoot growth in the leaf notches, it was observed also that the leaf has an 

 accelerating influence upon the geotropic curvature of the stem itself. The 

 present article notes a number of studies by the author on the influence in this 

 connection of such factors as the presence, absence, or position of leaves ; split- 

 ting, decortication, or notching of the stem ; and combinations of these factors 

 on the degree of geotropic bending. 



It appears that in B. calycinum, the substances which induce root formation 

 tend to collect on the lower side of a stem placed horizontally, although roots 

 may appear also in notches on the upper side under conditions to be discussed 

 in a later paper. Leafless stems curve and form roots much more slowly than 

 do those having one or more leaves. The position and number of the leaves 

 influence in certain ways the geotropic curvature. Generally it appears that 

 each leaf sends shoot-forming substances toward the apex and root-forming 

 substances toward the base of the stem. The probable significance of these 

 and other observed facts is discussed. 



Th.e spontaneous negative geotropism of roots, Eva Mameli and Eligia 

 Cattaneo (Separate from Atti 1st. Bot. R. Univ. Pavia, 2. ser., 11 11916^, 

 pp. 12). — Concluding a study of negative geotropism and related phenomena 

 observable in Helianthus annuus and in some other plants, the authors state 

 that in spontaneous negative geotropism the root cap becomes shorter and more 

 obtuse than in case of roots positively geotropic. It presents an evident arrest 

 of development with complete absence of starch in that portion during that 

 stage, although starch appears in the stage immediately preceding a new 

 orientation of the rootlet consequent upon the development of diageotropism or 

 positive geotropism. In such case the starch is always found in the physically 

 inferior part of the cell. 



The behavior of certain gels useful in the interpretation of the action of 

 plants, D. T. MacDougal and H. A. Spoehe {Science, n. ser., 45 {1911), No. 

 1168, pp. 484-488). — The authors claim that the systematic endeavor to con- 

 struct a colloidal mixture which would display some of the fundamental 

 physical properties of protoplasm of plants has resulted in finding that a 

 mixture of substances of two of the three more important gi'oups of con- 

 stituents, carbohydrates, and proteins, shows the imbibitional behavior of 

 tissues and tracts of protoplasts of the plant. The differential action of such 

 colloidal masses in distilled water and acid and alkaline solutions is said to 

 yield many striking parallels with growth. 



The effect of continuously supplying water to plants by capillarity, L. 

 Daniel {Compt. Rend. Acad. Sd. [Paris], 163 {1916), No. 19, pp. 525-521).— 

 Several garden plants supplied with water permitted to percolate continuously, 



