(>(i PHYSIOLOGY. 



on a green color, and then we find that carbon conversion 

 begins. 



157. Chlorophyll and chloroplasts. — The green substance in 

 plants is then one of the important factors in this complicated 

 process of forming starch. This green substance is chlorophyll, 

 and it usually occurs in definite bodies, the chlorophyll bodies, 

 or chloroplasts. 



The matericil for new growth of plants grown in the dark is derived from 

 the seed. Plants grown in the dark consist largely of water and protoplasm, 

 the walls being very thin. 



158. Form of the chlorophyll bodies. — Chlorophyll bodies 

 vary in form in some different plants, especially in some of the 

 lovv^er 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. In oedogonium, another of 

 the thread-like algae, illustrated in fig. 95, the chlorophyll bodies 



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Fig. 55- 

 Section of ivy leaf, palisade cells above, loose parenchyma, with large intercellular spaces 

 in center. Epidermal cells on either edge, with no chlorophyll bodies. 



are more or less flattened oval disks. In vaucheria, too, a 

 branched thread-like alga shown in fig. 106, the chlorophyll 

 bodies are oval in outline. These two plants, oedogonium and 



