COLOR 



173 



of the entire leaf. The intensity of the Hght 

 ^vhich induces a maximum of activity in any 

 plant, and which it may receive without dam- 

 age, is determined by its specific constitution. 



B 



Fig. 19. — Transverse Sections through the Frond of 

 Lemna trisulca (Duckweed), Showing Different Posi- 

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

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

 darkness. After Stahl. 



In the greater majority of plants the eflScien- 

 cy of the chlorophyll increases in tempera- 

 tures up to 35° centigrade, varies from 35 to 



