PRINCIPAL GROUPS OF PLANTS. 



45 



fact that the conidiophores rise to the surface of the leaves 

 where the spores are discharged, forming powdery patches. 



Black Mold. A common example of the Zygomycetes is 

 furnished by the " black mold," Mucor Mucedo. The mycelium 



FIG. 23. B, richly branching mycelium (m) of the mold Phycomyces nitens showing 

 upright hyphae bearing sporangia (g). A, C, D, the common black mold Mucor Mucedo. 

 A, sporangium with columella; C, germination of zygospore (z), with formation of hypha 

 (k), and sporangium (g); D, earliest stages in the development of a zygospore. the hyphal 

 branches (b) showing adjoining ends (a) cut off by cross walls. After Sachs. 



of this plant is coenocytic, thread-like, very much branched, and 

 profusely developed, much like that of Phycomyces nitens (Fig. 

 23, B). This mold is widely distributed, causing trouble in the 

 spoiling of many sugar- and starch-containing substances in the 

 household, including preserves, syrups, fruits, etc. In fact, a 



