GERMINATION OF ZYGOSPORES 



123 



three distinct types of germination, (a) All the spores from 

 the germ sporangia of Sporodinia grandis are pure homothaUic, 



that is, are all (H ). {b) All the spores from any single germ 



sporangium of Miicor vmcedo are either all ( + ) or else all ( — ) ; 



Fig. 39. Blakeslea trispora. A. Portion of sporangiophore from which the 

 sporangia have been removed from the capituli. B. Three-spored sporangia 

 borne on sterigma-like processes over the surface of the capitulum. C. 

 Sporangium with sterigma at the base. D. Sporangiospore, provided with 

 tufts of slender hair-like appendages. F and G. Stages in zygote forma- 

 tion. E. Sectional view of nodding sporangia that have not been noted 



to occur except in culture. 



that is, each is unisexual, (c) \n ?hy corny ces miens the spores 



are (-f ), ( — ), and (-| ); that is, some are unisexual and others 



bisexual. Cytological evidence in support of what may logically 

 be assumed to transpire to account for these phenomena has been 

 presented by Cutter (1942). 



The 15 species of Alucorales studied by Cutter represent four 

 patterns of nuclear behavior. In the Mucor type all functional 

 zygospore nuclei fuse in pairs; immediately after, reductional di- 

 vision takes place, and the zygospores then become dormant. In 



