CHLOROPHYLL AND ASSIMILATION 135 



TABLE XXVII 

 Relation of Chlorophyll Content to Assimilation 



It will be seen that these plants fall into two classes. 

 The first five have an assimilation number of about 6, 

 the last two of about 12. All the plants examined by 

 Willstatter fall into one of these two groups. The con- 

 ditions of experiment were such that neither an increase 

 of light nor of carbon dioxide supply could increase the rate 

 of assimilation, so that the figures may be taken as expressing 

 the plant's maximum capacity for a teinperature of 25° C. 

 Taking the plants of either group, we see then that there 

 seems to be a very close relation between the assimilating 

 capacity and the quantity of chlorophyll present. The 

 plants of the second group, however, are able to employ 

 their chlorophyll to much better purpose than the others. 

 As Willstatter points out, they are plants which are remark- 

 able for rapid and luxuriant growth. The amount of 

 chlorophyll available is, therefore, not the sole factor in 

 producing vigorous assimilation. The same amount can 

 allow in Cucurbita double the rate shown by Ampelopsis. 

 In the latter, at least, it is therefore in excess. 



This is further demonstrated by the behaviour of young 

 leaves. In these the assimilating capacity is greater, related 

 to the amount of chlorophyll, than in old leaves ; as the leaf 

 matures the amount of chlorophyll increases, and so, in 

 general, does the assimilating power, though not to the same 



