1918.] AGRICULTUEAL BOTANY. 821 



Osmotic pressure in animals and plants, W. R. G. Atkins {Set. Prog. 

 [Lo7idon], 11 (1917), No. 44^ pp. 562-577). — Summing up observed results m 

 comparative studies of osmotic pressures iu animal and plant cells, the author 

 notes that in this respect, as v^'ell as in other phases of their physiology, there 

 is an abbreviated recapitulation of phylogeny in case of members of each 

 division, notwithstanding the difference in the conditions under which the two 

 great divisions of living matter have developed. 



It is stated that in animal cells the upper limit of osmotic pressure is not 

 far from 7.5 and that within the body each cell may be considered as a water 

 dweller, being in osmotic equilibrium with the other cells and the intercellular 

 solutions. In primitive naked plant cells, in free sperms, and in unfertilized 

 ova, the osmotic relationships are much the same as those for lower animals. 

 In case of higher plants, however, the presence of a comparatively inextensible 

 cellulose wall brings about entirely new conditions (which are discussed), 

 and as a result very great differences as regards osmotic pressure exist in the 

 different tissues. In this division a very great part of this osmotic influence 

 is due to nonelectrolytes, sugars preponderating. The effect of light upon 

 chlorophyll-bearing organs is considered by far the most powerful of the many 

 causes which influence osmotic pressure in plants. 



The main purpose of this paper is to emphasize the differences existing as 

 regards osmotic pressure in animals and in plants. 



Carbon assimilation, I. Jokgensen and W. Stiles {New Phytol., U^ {1915), 

 Nos. 8-9, pp. 240-250; 10, pp. 281-294; 15 {1916), Nos. 1-2, pp. 11-23; 3-4, pp. 

 85-96; 5-6, pp. 117-135, figs. 6; 7, pp. 144-160, figs. 7; 8, pp. 176-193; 9-10, pp. 

 205-232, figs. 4; 16 {1917), Nos. 1-2, pp. 24-45, fig. 1; 3-4. pp. 77-i04).— This is 

 mainl5' a review of recent work by different investigators on the pigments of 

 the green leaf and on the processes connected with them. 



Buffer processes in the metabolism, of succulent plants, Jenny Hempel 

 iCompt. Rend. Lab. Carlsberg, 13 {1917), No. 1, pp. 130, figs. 16).— The author 

 gives an account of investigations carried out on ijlants subjected to widely 

 diiferent external conditions, designed to determine the concentration of 

 hydrogen ions in the cell sap extracted from leaves and the relation of such 

 concentration of hydrogen ions to the quantity of contained acid as shown by 

 titration, and to estimate the importance of such relation. 



It is stated that in the sap from leaves of succulent plants the concentration 

 of hydrogen ions varies, but is determined by the quantity of titratable acid 

 and the quantities of dissociated malates. In certain saps (possibly in all 

 succulents) acid is never associated with acid salt, though varying quantities 

 of acid salt and normal salt occur together in a mixture of a marked buffer 

 character. The facultj^ of producing and accumulating acids varies greatly in 

 succulents. It may stand in causal relation to the quantity of dissociated 

 malates. Species vary greatly as regards the distance between the litmus 

 and phenolphthalein points as shown by titration, older leaves sometimes 

 exceeding younger ones in this respect, and the quantity of aluminum malate 

 appearing to be influential in this respect. Sap from seedlings of lupines 

 {Lupinvs albus) showed nearly uniform values for the concentration of 

 hydrogen ions. Fluid from nonstimulated pitchers of Nepenthes showed 

 indefinite concentrations of hydrogen ions as contrasted with the fluid from 

 pitchers subjected to stimulus. By means of lacmoid paper an approximate 

 value is obtainable for the concentration of hydrogen ions in a liquid when 

 such concentration falls within certain limits. 



A study of stomata, L. Rehfous {Bui. Soc. Bot. Geneve, 2. scr., 9 {1917), 

 No. ^-6, pp. 245-350, figs. 135). — The author gives an extended account of 



