294 Physiologie. 



it, in such a manner as to indicate an approximate proportio- 

 nality between the photosynthetic work it can accomplish, and 

 the partial pressure of the gas in the air around it. 



With regard to the effect of increased proportion (2 — 4 times 

 as much) of carbon dioxide in the air upon the nutrition of 

 plants, it is shown that whilst the activity of photosynthesis is 

 increased, the gain in dry plant-weight is less than in air of 

 normal composition. 



The effect of increased proportion of carbon dioxide upon 

 the general habit of the plant is well-marked: the internodes 

 are shorter and thicker; the axillary buds develope into branches 

 giving the plant a more bushy appearance; the leaves are 

 smaller, consequently the Ieaf-area is diminished; and the 

 development of flowers is almost entirely inhibited. 



The authors conclude that a sudden increase of carbon 

 dioxide in the air to the extent of two or three times the 

 present normal amount, would result in the speedy destruction 

 of nearly all our flowering plants. Vines. 



Charpentier, P. G., Sur l'assimilation du Carbone par 

 une Algue verte. (Comptes rendus des Seances de 

 l'Academie des Sciences. Tome CXXXIV. 17 mars 1902. 

 p. 671.) 



L'auteur a cultive ä l'etat de purete le Cystococcus humi- 

 cola dans une Solution ainsi composee: 



Sulfate de magnesium 1 gr. 



Phosphate bipotassique 2 gr. 



Nitrate de potassium 2 gr. 



Nitrate de calcium gr., 05 



Sulfate ferreux traces 



Glucose 10 gr. 



Eau 1000 gr. 



La plante y pousse tres bien et forme une couche d'un 

 beau vert, sur le fond du vase, d'autant plus abondante que le 

 liquide est en couche plus mince et que l'air a un plus libre 

 acces. Mais sa croissance est ä peu pres la meme, que l'air 

 soit prive ou non de CO 2 , car c'est principalement au glucose 

 qu'elle emprunte le carbone qui lui est necessaire. Maintenu ä 

 l'obscurite, pendant tout le cours de son developpement, le 

 Cystococcus est vert par la chlorophylle qu'il renferme mais il 



croit beaucoup moins vite qu'a la lumiere. 



C. Sauvageau (Bordeaux). 



COPELAND, E. B., The Mechanism of Stomata. (Ann. Bot. 

 Vol. XVI. No. 62. June 1902. p. 327—364.) 



The author finds that the mechanism of opening of the 

 Stoma is by no means uniform in plants: he distinguishes the 

 following types: 



