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TEXTBOOK OF BOTANY 



green plants.- The green plants in turn are dependent upon certain oxi- 

 dized compounds from the non-green plants. Dependent relations be- 

 tween green and non-green plants briefly outlined above are indicated in 



Fig. 227. Diagram of some dependent relations among green and non-green plants. 



Figs. 227, 228, and 233. Others will be indicated in later chapters. 

 In the absence of adequate data we have assumed that the first food 

 made from carbon dioxide by autophytic bacteria is some kind of sugar, 

 as it is in green plants. 



Saprophytic plants. These are the organisms that cause most of the 

 decay of organic matter. They live upon and obtain food from the dead 

 bodies of plants and animals, and also from the products of all living 

 organisms. Some of them have enzymes that digest cellulose, pectic com- 

 pounds, and even kerosene and coal. Digestion of these substances occurs 

 outside the body of the plant. Their enzymes, therefore, must diffuse 

 from the living cells where they are synthesized into the surrounding 

 media. 



- Probable exceptions are the sulfur bacteria. Although they utilize the sulfur reduced by 

 other plants, it is possible that sulfofying bacteria could survive independently by utilizing 

 the sulfur and sulfur compounds (SO2 and H„S) emitted by volcanoes. The iron bacteria 

 also have possibilities of living independently of other plants. 



