658 



THE AMERICAN NATURALIST 



[Vol. XLIJ 



tures started at the full value indicated by a theoretically 

 constant coefficient, but that the protoplasm was unable 

 to keep up the velocity, and the rate declined. It must 

 be borne in mind here that quite probably no chloroplast 



since the first appearance of green cells upon the earth 

 had ever been called upon for anything like such a gas- 

 tronomic effort as these cherry-laurel leaves in question. 

 It is not to be wondered that their capacities speedily 

 declined at such a banquet, and that the velocity-reaction 

 of anabolic synthesis traces a falling curve in spite of the 

 keeping up of all the factors concerned, to wit, tempera- 

 ture, illumination, and supply of C0 2 . This decline is not 

 permanent, but after a period of darkening the power of 

 assimilation returns. Physical-chemical parallels can 

 easily be found among cases where the accumulation of 

 the products of a reaction delays the apparent velocity 

 of the reaction, but this complicated case may be left for 

 further research. 



In relation to assimilation, then, we must say that 



