1916] AGEICULTUEAL BOTAjSTY. 223 



curve of intake is by no means so simple as tliat reported for barley by Brown 

 and Worley (B. S. R., 28, p. 226). The temperature coefficient for the rate 

 of intake is said to be decidedly lower than the Van't HoflE coefficient for 

 chemical processes and considerably lower in the case of Xanthium than the 

 values obtained with barley seeds. It is considered that the conclusions reached 

 by Brown and Worley are not generally applicable. 



Seed sterility and delayed germination in CEnothera, B. M. Davis (Abs. in 

 Science, n. ser., 43 {1916), No. 1104, V- 291). — From a study of 50 or more 

 species, races, and hybrids of CEnothera, the author reports considerable seed 

 sterility and delayed germination. A method is suggested for rapidly forcing 

 germination and for preserving for examination the residue of sterile seedlike 

 structures. 



The influence of the medium upon the orientation of primary roots, R. M. 

 HoLMAN {Abs. in Science, n. ser., 43, {1916), No. 1105, pp. 328, 329).— Bj the use 

 of media whose resistance to penetration by the root tip could be widely 

 varied, the author was able to cause roots to behave very nearly as in the 

 air or in the same manner as in the earth, according as the medium was 

 loose or considerably compressed. These experiments are believed to indi- 

 cate that the effect of the medium is primarily, if not exclusively, mechanical. 

 Secondary roots of the species investigated behaved in a manner similar to the 

 primary roots, reacting more promptly in media offering considerable resistance 

 to penetration than in looser media. 



The root growth of forest trees, W. B. McDougall {Abs. in Science, n. ser., 

 43 {1916), No. 1105, p. 324). — Observations made on the roots of Acer saccha- 

 rinum, Tilia americana, Carya alba, and Quercus macrocarpa are reported for 

 the growing season and during the winter from April, 1914, to September, 1915. 



It was found that the root growth of forest trees begins as early in spring 

 as the soil is warm enough for absorption and ceases in autumn when the soil 

 becomes too cold. No summer resting period was found necessary. Where a 

 summer resting period was observed, it was found to be due to a lowering of the 

 water supply and not to any inherent tendency to periodicity. 



The influence of electrical conditions in plants on the absorption by their 

 roots of nutritive substances, D. Shushak (Chouchak), {Zhur. Opytn. Agron., 

 16 {1915). No. 4, pp. 249-269. figs. 5).— In continuation of previous work (E. S. 

 R., 32, p. 32S), the author states that experimental tests as tabulated show that 

 up to a certain point the direction and intensity of the electric current passed 

 through a plant condition the absorption of cations and of anions and determine 

 the rate thereof. These variations in the absorption rate are apparently inde- 

 pendent of electrolysis, as they do not follow Faraday's law. Dead and living 

 wheat plants give results of the same character. 



These facts suggest that some substances, probably colloidal, may be differ- 

 ently polarized under the influence of charges of different sign and intensity up 

 to certain limiting values. Such charges are said to be directly observable in 

 the absence of a current by the use of a delicate electrometer and to be modi- 

 fiable by the addition of salts. The variations in rapidity of absorption of 

 cations and in intensity of current show a degree of correspondence. It is 

 thought that the electrical conditions in the roots of plants may be of signifi- 

 cance in plant nutrition. 



The structure of the bordered pits of conifers and its bearing upon the 

 tension hypothesis of the ascent of sap in plants, I. W. Bailey {Ahs. in 

 Science, n. ser., 43 {1916), No. 1105, p. 329). — Attention is called to the tension 

 hypothesis of the ascent of sap in plants, ^yhich, as interpreted by Dixon, postu- 

 lates continuous columns of water that are entirely free from bubbles of air or 

 gas. The pit membranes of conifers are said to be not entire septa, and not to 



