ABSORPTION AND USE OF CARBON 



227 



plish the breaking up of the carbon dioxide molecule is pre- 

 sumably derived from the radiations absorbed. The remainder 

 of the molecule of carbon dioxide, with its unsatisfied chemical 

 affinities, is further acted upon by protoplasm of the chloroplast, 

 and as the result of the synthetic processes a carbohydrate, gener- 

 ally cane sugar, is formed. 

 The successive steps in the 

 construction of this com- 

 plex compound, and the 

 part played by the plasma 

 are wholly unknown, and 

 even the outline given is 

 based in great part upon 

 theoretical considerations. 1 

 The entire process is known 

 as photosynthesis. The 

 products may be diffused 

 a rapidly as formed, and 

 undergo further combina- 

 tion to form nitrogenous 

 bodies, or they may ac- 

 cumulate because of the 

 great activity of the chloro- 

 plasts. The accumulation 

 may appear as glucose in 

 cells of some plants, al- 

 though in the greater num- 

 ber of species the saturation 



of the cell with the photosynthetic products is followed by their 

 condensation into some insoluble form as starch. During the 

 day the action of light causes the accumulation of the surplus 

 products, which are more or less completely translocated from 

 the green cells during the succeeding period of darkness. 



1 Went, A. F. C. Chemisch-physiologische Untersuchungen ueber das Zuckerrohr. 

 Jahrb. Wiss. Bot. 31:289. 1898. 



Fig. 112. Cultures of hemp in : neutral solid 

 substratum. A complete nutrient solution has 

 been added to I, and the plants have attained 

 a height of 1.5 meters : a solution lacking 

 potassium nitrate has been added to the sub- 

 stratum in II, and only the sterile substratum 

 placed in the pot in III. After Ville. 



