Fungus Diseases of Plants 



147 



and, therefore, can not make their food like the algae and 

 the higher green plants. They are called dependent plants. 

 There are many kinds. Plants like the fungi are thought 

 by scientists to be greatly changed algae that have lost 



Fig. 88. Spores, or seeds, of the fungus producing the "rust" of wheat. A, 

 summer spores, or "red rust" stage; B, same germinating on surface of 

 leaf; C, autumn spores, or "black rust" stage. 



the power of carbon assimilation, and are, therefore, 

 dependent on host plants to supply the food they need. 

 They are called independent plants. Many higher 

 plants are dependent in the same way, such as the 

 dodder, or "love vine.' 7 They grow under many con- 

 ditions, but all must get their food from plant or animal 

 substance. Species that get their food from living plants 

 or animals, are called parasites. Those that get their 

 food from dead plant or animal remains, are called 

 saprophytes. Some species of fungi may get their food 

 from either living or dead organisms. The red or black 

 powdery mass which we call "rust," is only a mass of 

 spores (one-celled seeds) of the fungus causing the 

 disease. The body of the plant exists as a lot of threads 

 inside of the host-plant and is not visible to the eye. 

 When magnified by the microscope, these fine hyphsa 

 may be plainly seen. 



