320 



PROCEEDIXGS OF THE ACADEMY OF 



[^lay, 



May 7. 

 The President, Samuel G. Dixon, jNI.D., in the Chair. 

 Twenty-two persons present. 



May 14. 



The President, Samuel G. Dixox, M. D. , in the Chair. 



Fifteen persons present. 



Demonstration that Plants (jive off Oxyrjen. — Dr. Ida A. Keller 

 remarked that there is no process in plant life of greater import- 

 ance than the evolution of oxygen in the synthetic preparation of 

 starch by the chlorophyll in the presence of sunlight. In teaching 

 such physiological phenomena it is important to demonstrate them 

 in such a manner as to leave no doubt in ihe mind of the pupil. 

 The method usually described (by Detmer and others) to illustrate 

 this process is quite familiar to all students of botany. It is repre- 

 sented by figure 1. 



A piece of Elodea Canadensis is placed in a jar containing 

 water. A funnel is inverted over the plant and a test tube filled 

 with water is inverted over the funnel. The water is charged with 

 carbon dioxide and the apparatus is placed in the sunlight. Ver}' 

 soon bubbles of gas are disengaged and collected in the test tube. 

 The gas may then be shown to be oxygen. Oq account of ihe 

 limited capacity of the apparatus employed and the comparatively 

 small extent of the assimilating surface, this method is not very 

 useful for purposes of demonstration because of the small volume 

 of gas liberated. 



2 s 



She had found the following extremely satisfactory : — A receiver 



