MOLDS 



49 



reproduction (Figs. 32 and 33). In the mucors, the mycelium is usually 

 richly developed within and often also on the surface of the substratum; 

 asexual reproduction is accomplished by spores borne as conidia or 

 borne within sporangia; and sexual reproduction is accomplished by 

 the conjugation of special branches from the mycelium forming zygo- 



FIG. 32. FIG. 33. 



FIG. 32. Mucorineos. Mucor. From Tabula Botanical, showing sporangia 

 originating from mycelium, spores and spore germination, and the formation of 

 zygospores in a heterothallic species (diagrammatic). (Reduced one-half.) (By 

 permission of A. F. Blaskeslee.) 



FIG. 33. MuLorinea. Mucor, Rhizopus. A, B, C, D, Formation of the zygo- 

 spores from conjugating branches; E, section of Z>; F, mature zygospores in section; 

 G, germination of zygospores; H, diagram pf fruiting stolons of Rhizopus nigricans; 

 K, section of sporangium during spore formation, highly magnified (From Tabula 

 Botanica.) (Reduced one-half.) (By permission ofA.F. Blaskeslee.} 



spores (Figs. 32 and 33). The typical mucors produce sporangia as 

 capsule-like dilations at the ends of erect fertile hyphae, each con- 

 taining many spores. Septa are commonly developed in the mycelium 

 when sporangia begin to appear. These fertile hyphae may be micro- 

 scopic or attain a length of several centimeters. 



Important Species. Perhaps the commonest form is Rhizopus 

 nigricans (syn. Mucor stolonifer), the black mold of bread, a cosmo- 



4 



