FUNGI AND FUNGOUS DISEASES OF PLANTS 235 



undergrowth one may find large numbers of these saprophytic 

 plants growing upon decaying organic matter. By breaking 

 open an old log or branch of wood (fig. 183) upon which 

 fungi are growing, or by upturning rich soil, one often finds the 

 extensively interwoven, mold-like saprophytic growth. This 

 internal growth gathers nourish- 

 ing material for the whole depend- 

 ent plant, and at the same time 

 helps to bring about the decay of 

 the material upon which it lives. 



221. The algae-fungi. There are 

 many different groups of fungi, 

 and they are often so unlike that 

 it is at first hard for the student 

 to regard them as belonging to 

 the same larger group, the fungi. 

 In the case of some of the molds, 

 if the thread-like fibers of which 

 they are composed were to pos- 

 sess chlorophyll, they would ap- 

 pear quite similar to some of the 

 algae. Because of this structural 

 resemblance one group of fungi is 

 called the algae -fungi (PJiycomy- 

 cetes, meaning "algae-fungi"), 

 that is, fungi that are more like 

 algae than are other fungi. Most 

 of the saprophytic molds and a 



good many destructive parasites belong to the algae-fungi. 

 A few types will show their nature, how they live, and how 

 they affect the things upon which they live. 



222. Bread mold. If a piece of slightly moistened bread is 

 placed in a glass jar or in a covered dish for a few days, an abun- 

 dant supply of mold soon appears upon it. Several kinds of 

 molds may develop at the same time under such conditions, 

 but the common bread mold, or black mold, is the one which 



FIG. 183. A section through a 

 dead branch of a cottonwood tree 



Note the white patches of internal 

 mycelium and the external spore- 

 producing bodies of the fungus, a 

 Polyporus 



