1897.] NATURAL SCIENCES OF PHILADELPHIA. 143 



animal organisms but with all plants also. It is the well-known 

 process of respiration, that which Gautier has called "the animal 

 life of plants." The method I desire to describe is of great sim- 

 plicity, and it yields conclusive results within an hour, provided 

 the light be sufficiently strong ; it does not necessitate the collection 

 of any appreciable volume of gas, and it demonstrates both phases 

 of the endothermic reaction. 



Hematoxylin, the chromogen of logwood, is peculiarly fitted to 

 be an indicator in a case where it is desired to recognize the pres- 

 ence or absence of carbon dioxide and the evolution of nascent 

 oxygen, the solvent being ordinary water from spring or river con- 

 taining its usual traces of various mineral matters. Under the in- 

 fluence of carbon dioxide, the hematoxylin dissolved in such water 

 loses its normal rosy or slightly bluish-red tint, and turns to a yellow 

 with a tinge of brown. In the presence of nascent oxygen, on the 

 other hand, the light red hue deepens momentarily, and ends by be- 

 coming a very deep blood red. The latter change is in a manner 

 permanent, but the former is reversible, i. e. the rosy red color 

 returns when the carbon dioxide is removed. These well-known 

 color reactions are of great delicacy, and are used in the following 

 way : 



!■■■■■!■■■ imi iipiini iiiTnrrr 









ess: 



A sufficient quantity of water is taken to fill all of the tubes shown 

 in the figure, and the dish up to the mark DE. This is tinted with 

 a sufficient quantity of a freshly made solution of hematoxylin. 

 The color should be a very pale hue of red. The tube A is then 



