VELOCITY OF REACTION. HETEROGENEOUS SYSTEMS 137 



of Typka latifolia increases with the content of carbonic 

 acid in the surrounding air, and nearly proportionally with 

 it, up to about 2 per cent. An optimum occurs at about 6 

 per cent. At further increase the assimilation decreases, 

 but very slowly. This process was recently studied by 

 Miss Gabrielle Matthaei, 1 who found that the assimilation 

 of carbonic acid by a leaf of Pnmus Laurocerasus increases 

 with temperature in the following manner (for a leaf of 

 50 cm. 2 and in one hour) : 



The process is in all points analogous to the action of 

 ferments. The chlorophyll may here be regarded as the 

 acting ferment. The value of /* is 11,940. In these 

 figures we observe already a greater increase at lower tem- 

 perature than the formula indicates. If the temperature 

 falls below o, the assimilation sinks very rapidly, so that 

 at 6 C. the observed figure is only 0.2 mg., correspond- 

 ing to a value of /* between o and 6 C., about ten times 

 greater than between o and 37. Above this latter tem- 

 perature again the assimilation sinks with rising tempera- 

 ture until the leaf dies. This evidently depends on a de- 

 struction of the functions of the chlorophyll at very low or 

 at higher temperatures. 



1 Gabrielle Matthaei : Phil. Trans. Roy. Soc., Ser. B, 197. 47 (1904). Cf. 

 Kanitz: Zeitschr.f. Elektroch.^ No. 42 (1905). 



