xxx DISTRIBUTION OF FOOD-MATERIALS 411 



rhizoids are dependent upon the green cells of the leaves 

 for their supplies. Like other cells devoid of chlorophyll 

 they .are unable to make use of carbon dioxide as a source 

 of carbon, but require ready-made carbo-hydrates, the 

 manufacture of which is continually going on, during 

 daylight, in the chlorophyll-containing cells of the leaves. 

 This striking division of labour is the most important 

 physiological difference between mosses and the more lowly 

 organised green plants described in previous lessons. 



