INCOME OF THE PLANT. 



147 



hGclies or (Jiromatophores j for plants wliicli, like fungi, etc., are 

 devoid of chlorophyll are unable thus to acquire enei'gy. Enter- 

 ing the chlorophyll-bodies, the kinetic energy of sunlight is ap- 

 plied to the decomposition of carbon dioxide (COJ and water 

 (H^O). Alter passing through manifold but imperfectly known 

 processes, the elements of these substances linally reappear as 

 starch (CjIIj^OJ often m the form of granules imbedded in the 

 chloro^^hy 11 -bodies, and free oxygen, most of which is returned 



INCOME OF PTERIS. 



to the atmosphere. Thus the leaf of Pteris in the light is con- 

 tinually absorbing carbon dioxide and giving forth free oxygen. 



Carbon dioxide and water contain no potential energy, since 

 the affinities of their constituent elements are completely sat- 

 isfied. Starch, however, contains potential energy, since the 

 molecule is relatively unstable, i.e., capable of decomposition 

 into simpler, stabler molecules in which stronger affinities are 



* It lias been generally believed that plants are unable to make use of free 

 atmospheric nitrogen, but recent investigations have disproved this view for 

 certain species. 



