1920] AGRICULTURAL BOTANY. 633 



tli»> share of the geneticist in the final elucidation of the pijjfuient situation must 

 he to provide tlu' chemist witli materials of known factorial composition. 



Comparative studies on the carotin and xanthophyll content of green 

 and autumn yellow leaves, E. Gokkrig (Hot. Centbl., Beihefte, 35 (1918), 1. 

 Alt., No. 2, pp. 3.'f2-S9/f). — It is stated that carotin and xanthophyll participate 

 in the necrobiotic phase of autunni leaf coloring, the latter pigment at least 

 doubling the former as regards quality but the ratio varying with the species. 

 It is thought that quantitative genetic relations do not hold between the green 

 and the yellow colorants of the chloroplasts. Carotin and xanthophyll differ 

 greatly as regards such characters as sensitivity to light and temperature. 



Exudation of water by Colocasia antiquoruni, M. G. Flood {Sci. Proc. Roy. 

 Dublin Soc, n. ser., 15 (1919), No. 36, pp. 506-512, pis. 2, fig. i).—E?:peri menta- 

 tion is described which is considered to show that there is no spwial tissue in 

 the leaf tip of C. antiqtioruin serving as a gland or epithem for the secretion 

 given up by the leaves. No membrane for filtering the water was found to 

 intervene between the water channels and the depression in the leaf. Transfer 

 arrangements in the plant would indicate that cells lower down may secrete 

 and filter the water. No special cells for such work outside the root have been 

 demonstrated. 



On some factors affecting the concentration of electrolytes in the leaf 

 sap of Syringa vulgaris, T. G. Mason (Sci. Proc. Roy. Dublin Soc, n. ser., 15 

 (1919), No. Ji6, pp. 651-666). — An account is given of attempts to work out a 

 plan for making corrections for the viscosity of sap in the determination of con- 

 centrations of electrolytes in plant cells by means of conductivity observations. 

 The osmotic pressure of the cell is frequently due mainly to electrolytes, but 

 the presence of solutes which are neither electrolytes nor sugars is not excluded. 

 Considerable fiuctuations have been indicated in the concentrations of electro- 

 lytes in the leaf sap of S. vulgaris growing in different localities. There is a 

 tendency for the concentration of electrolytes to vary inversely with that of 

 nonelectrolytes. It is suggested that these fluctuations may be associated with 

 the rate of carbon assimilation, which determines the rate at which electrolytes 

 are removed from solution in metabolism. 



The existence of daily growth rings in the cell wall of cotton hairs, W. L. 

 Balls (Proc. Roy. Soc. [London], Ser. B, 90 (1919), No. B 634, PP- 5.'f2-555, pis. 

 S, figs. 4; abs. in Oard. Chron., 3. ser.. 66 (1919), No. 1115, p. 23^).— As a result 

 of studies outlined, the author considers it well established that the primary 

 wall of the seed hairs in cotton contains very small amounts of cellulose; that 

 the secondary thickening of the wall proceeds intermittently under normal 

 Egyptian field crop conditions, being ari*ested each aftei'noon ; that the cellulose 

 of each hair is arranged in 25 growth rings, each being the result of one day's 

 growth with the exception of that of the primary wall ; and that the so-called 

 fuzz hairs are analogous with the lint hairs, though they have coarser and 

 plainer growth rings. 



Outside the cellulose of the primary wall the hairs are covered by a cuticle, 

 bearing wax, which is structurally and historically identical with the cuticle 

 of the testa while structurally and chemically distinct from the cellulose. The 

 secondary wall, but not the primary, is traversed obliquely to the hair axis 

 by simple pits (rarely visible except in the living hair), which cause the twist- 

 ing and convolutions of the hair after death (which are described). 



The method employed utilizes a simple but special sort of ultramicroscopy, 

 the growth rings being but about 0.4 fi in thickness. 



The layers are due to arrest of growth each afternoon during the hot days. 

 In which the lint grows in thickness after forming, by growth in length, the 



