FOLIAGE LEAVES : FtTNCTION, STEUCTURE. ETP. 



29 



bubbles arc numerous. That this activity' holds a definite 

 relation to light may be proved by gradually removing the 

 vessel containing the leaf from the liglit. As the light 

 diminishes the bubbles diminisli in number, and when a. 



Fig. 23. Ad experiment to illustrate the giving off of osygen in tlie process of photo- 

 synthesis. 



certain amount of darkness lias been reached the Imbbles 

 will cease entirely. If now tlie vessel be brouglit back 

 gradually into the light, the bubbles will reappear, more 

 and more numerous as the light increases. That this gas 

 being given off is oxygen may be proved by collecting the 



