LIFE HISTORIES OF FUNGI 257 
stratum is also usually moist. Partly as a result of 
their presence, the substratum on which they grow is 
usually disintegrating with decay. From these facts 
Rhizopus is called a saprophyte. 1 The most common 
species is Rhizopus nigricans. 
249. How Obtained. Rhizopus, or almost any other 
filamentous fungus, may be readily obtained by sowing 
its spores on a suitable substratum. But, unlike the 
higher plants, Rhizopus may ordinarily be obtained merely 
by exposing moist bread, or other nutritive substance, to 
the air. In the course of time, without one's sowing any 
spores, colonies of the plant will appear, and this clearly 
demonstrates the very interesting fact that these spores 
are always floating in the air in greater or less abundance. 
When the moist bread is exposed, some of the floating 
spores come to rest upon it, and there, under favoring 
conditions of moisture, temperature, and light they 
germinate, and develop new plants. 
250. Description of Plant Body. The plant body of 
Rhizopus (Fig. 185) consists of a slender, thread-like 
filament, called the mycelium, branching freely, devoid 
of chlorophyll, and growing over the surface of the 
substratum. The threads of mycelium are termed 
hyphcB. Careful examination with the microscope dis- 
closes the fact that the hyphse are largely or wholly 
aseptate, that is, not divided by cross-walls or septa. 
The plant body, therefore, consists of one cell, though 
there are several to many nuclei distributed through the 
cytoplasm; such a structure is termed a coenocyte. 2 
1 From the Greek, sapros (<rewrp6s), rotten, + phyton (<pvr6v~), a plant. 
2 Greek, KOIVOS (koinos), common, + KVTOS (kutos), a hollow (cell). 
17 
