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 
4 4 
Gametangium Gametangium 
4 4 
(+) Gamete (-) Gamete 
Conjugation 
Zygospore 
4 4 
Germ-tube 
4, 4 
Sporangium 
\, } Reduction 
(+) Spores (-) Spores 
4 4 
(+) Mycelium ( ) Mycelium 
4 4 
Sporangium Sporangium 
4 4 
(+) Spore ( ) Spore 
