7 6 BOTANY. 



is changed from its attraction in the molecule of carbon dioxide 

 to its attraction in the molecule of starch, the process has 

 been termed carbon assimilation. But since it is not truly an 

 assimilatory process, and because sunlight is necessary in the 

 first step of the conversion, it has also been recently termed 

 photosyntax ox photosynthesis. These terms, however, seem in- 

 appropriate, since the synthetic part of the process is not known 

 to be due to the action of light. In the presence of chlorophyll 

 light reduces the carbon dioxide, while the synthetic part of the 

 process may not be influenced by light. For popular treatment 

 the term carbon conversion was proposed in the author's larger 

 " Elementary Botany." But this is also an unfortunate term, 

 and he would now propose the simple term, starch formation. 

 But there should be no objection to the use of the term carbon 

 assimilation, or photosynthesis. 



139. Fungi cannot form starch.- — If we should extend our 

 experiments to the fungi, which lack the green color so charac- 

 teristic of the majority of plants, we should find that starch 

 formation does not take place even though the plants are 

 exposed to direct sunlight. These plants then obtain carbo- 

 hydrates for food from other sources, as parasites from living 

 plants, and as saprophytes from dead Dlants, or from certain 

 plant products. 



III. Chlorophyll and Chlorophyll Bodies. 



140. Form of the chlorophyll bodies. — This green substance 

 of plants, the presence of which is necessary in the formation 

 of starch, is chlorophyll. It usually occurs in definite bodies, 

 the chlorophyll bodies. Chlorophyll bodies vary in form in 

 some different plants, especially in some of the lower plants. 

 This we have already seen in the case of spirogyra, where the 

 chlorophyll body is in the form of a very irregular band, which 

 courses around the inner side of the cell wall in a spiral manner. 

 In zygnema, which is related to spirogyra, the chlorophyll 

 bodies are star-shaped. In the desmids the form varies greatly. 



