FOLIAGE LEAVES: FUNCTION, STRCCTURE, ETC. 



29 



bubbles are numerous. That this activity holds a definite 

 relation to light may be proved by shading the vessel con- 

 taining the plant. When the light is diminished the bub- 

 bles diminish in number, and when sufficiently darkened 



^jyB^tirrM 



Fig. 23. An expcrirat'iit to illustrate the giving off of oxygen in the procet^s of photo- 

 synthesis, 



the bubbles will cease entirely. If now the vessel be again 

 illuminated, the bubbles will reappear, and the rapidity 

 with which the bubbles are formed will indicate in a rough 

 way the activity of the process. That this gas being given 

 off is mainly oxygen may be proved by collecting the 



