AGRICULTURAL BOTANY. 629 



numerous on the upper side of the leaves. The author inclines to the view 

 that the drought resisting capacity does not bear any close relation to num- 

 oer of stomata, but that it is related to the presence of a peculiar structure on 

 the epidermis of the leaves In the form of small special groups of absorbing 

 and storing cells, which are to be further investigated. 



Studies in the chlorophyll group. — XtX, The inconstancy of chlorophyll 

 quotients in leaves and their biological meaning, II. Bouowska and L. 

 Marchlewski {Biochcm. Ztschr., 57 {191S), No. 5-6, pp. Jt23-Jt2'J).— This is a 

 partial review of work previously reported by Jacobson and Marchlewski 

 (E. S. R., 28, pp. 110, 60S), with notes replying to some criticisms offered 

 thereto. 



The role of oxygen in germination, C. A. Shull (Bot. Gaz., 51 il91/f), No. 1, 

 pp. 64-e9).— In a previous study (E. S. R., 26, p. 531), the author found that 

 there was either a change in permeability of the seed coat of Xanthium or a 

 change in oxygen need of the embryo during the winter. It was believed that 

 a careful measurement of the oxygen used by the seed would show whicJi of 

 these changes occurred, and a preliminary report is given of results obluined 

 in studying the role of oxygen in the germination of this seed. 



In the experiments the two lower seeds were placed in one chamber of the 

 respirometer and the seed coats in the other chamber. In 22.5 hours the seeds 

 used 0.475 cc. of oxygen, while the seed coats used 0.098 cc, indicating that 

 possibly the seed coats were partly responsible for the respiration of the in- 

 tact seeds. I^ater the respiration of the lower and upper seeds under atmos- 

 pheric conditions was compared, and finally in atmospheres of oxygen. It was 

 found that the two lower seeds in the atmosphere used 0.687 cc. of oxygen in 

 42.3 hours, while the same number of lower seeds used 1.007 cc. in 12.5 hours 

 in 95 i)er cent oxygen. The upper seeds used 0.509 cc. in 43.2 hours iu the 

 atmosphere, and 0.4406 in 12.5 hours in 90 per cent oxygen. 



This seems to indicate that an increase in the oxygen supply brings about 

 an immediate and rapid Increase in the rate of oxygen absorption and an im- 

 mediate germination of the seeds. The author states that, owing to the com- 

 plexity of the oxygen rule in physiological processes, it is difficult to say which 

 function or functions are affected. It seems certain, however, that the oxygen 

 acts as a limiting factor on some function. The exact method by which the ab- 

 sence of oxygen delays germination, it is said, can be determined only by fur- 

 ther investigation. 



Studies on the assimilation of atmospheric nitrogen by yeast and fungi, 

 P. LiNDNEii and C. W. Naumann {Wch7ischr. Bran., 30 (1913), No. 41, pp. 

 5S9-592). — Reviewing briefly recent contributions in this connection and dis- 

 cussing repeated tests made with Endoblastodcnna salmonicolor, Saccharo- 

 tnyces farinosus, and O'idium lactis, the authors conclude that in the experi- 

 ments cited atmospheric nitrogen was not assimilated by these forms. 



The relation between the transpiration stream and the absorption of 

 salts, H. Hasselbbing (Bot. Gaz., 51 {1914), No. 1, pp. 12, IS; ahs. in Science, 

 n. ser., 89 {1914), No. 998, p. 259). — An account is given of some experiments 

 conducted by the author during the winter of 1008-9 while connected with the 

 experiment station in Cuba. These were carried on with tobacco plants under 

 cheese-cloth shade and in the open to determine the comparative transpiration 

 of tobacco plants. 



The plants grown in the open absorbed about 28 per cent more water than 

 those grown under shade. The plants which absorbed and transpired the 

 greater quantity of water contained the smaller percentage and the smaller 

 absolute quantity of ash. It appears from these experiments that the absorp- 

 tion of salts by roots is independent of the absorption of water and that the 



