LIFE HISTORIES OF FUNGI 267 



() value, which fuse and form a zygospore. Such 

 mycelia are, of course, monoecious. 



The life-cycle of a dioecious mold is illustrated in 

 Fig. 192. 



268. Phycomycetes. Rhizopus nigricans represents the 

 group of Phycomycetes, lower fungi, often called "tube- 

 fungi." The group is characterized by the tubular hyphae 

 without septa. In this ccenocytic character they re- 

 semble the filamentous or tubular green algae (such as 

 Vaucheria, or "green felt"), of which they are supposed 

 to be degenerate descendants. 



259. Life -cycle of Rhizopus. The life-cycle of Rhizopus 

 may be diagrammed as follows: 



OUTLINE OF LIFE HISTORY OF RHIZOPUS 



(+) Spore (-) Spore 



4 4 



Mycelium Mycelium 



Gametangium Gametangium 



4, 4 



(+) Gamete (-) Gamete 



Conjugation 



Zygospore 

 Germ-tube 



44 



Sporangium 



4^ } Reduction 



