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. 



258. 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 coenocytic 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- I 



Mycelium Mycelium 



i i 



Gametangium Gametangium 



i 4. 



(+) Gamete (— ) Gamete 



Conjugati 



Zygospore 



4.4. 



Germ-tube 



4, I 



Sporangium 



4^ I Reduction 



(-|-) Spores ( — ) Spores 



i i 



(-I-) Mycelium ( — ) Mycelium 



i 4, 



Sporangium Sporangium 



4, 4- 



(+) Spore ( — ) Spore 



