﻿of the entire leaf. The intensity of the light 

 which induces a maximum of activity in any 

 plant, and which it may receive without dam- 

 age, is determined by its specific constitution. 



Fig. 19. — Transyekse Sections through the Frond of 

 Lemna trisulca (Duckweed), Showing Different Posi- 

 tions OF Chlorophyli, Bodies. A, position in diflfuse light ; 

 B, in strong light striking the surface perpendicularly ; C, in 

 darkness. After Stahl. 



In the greater majority of plants the efficien- 

 cy of the chlorophyll increases in tempera- 

 tures up to 35° centigrade, varies from 35 to 



