378 PHARMACEUTICAL BOTANY 
spores called endospores. The wall of the sporangium is beset 
with asperites of calcium oxalate. Springing from the base of 
the sporangiophores or aerial hypha, one or more stoloniferous 
hyphze traverse a portion of the surface of the substratum, and 
their tips, coming in contact with the substratum, swell up form- 
ing an adhesive organ or appressorium which branches out below 
into a cluster of spreading submerged hyphz and above into 
several aerial hyphz bearing sporangia. This method of growth 
proceeds until the entire surface of the nutritive medium is | 
covered with a dense fluffy mycelium. 
Fic. 280.—Black mold (Rhizopus nigricans). A, older plant; myc, mycelia; 
sph, sporangiophore; sp, sporangium; st, stoloniferous hypha produced by A, and 
giving rise at its tip to a new plant, B. Greatly enlarged. (Gager.) 
Rhizopus reproduces by two methods. The most common 
one is that of division by cleavage furrows. Inthis ASExUAL METHOD, 
a transverse wall is laid down in the sporangiophore near its tip. 
The terminal cell thus formed swells up, becoming globular in 
shape and its multinucleate protoplasmic contents, by progressive 
cleavage, become divided to form numerous spores within the 
wall of the sporangium or enlarged terminal cell of the sporangio-, 
phore. ‘The partition wall, separating the lumen of the sporan- 
gium from that of the sporangiophore, bulges into the sporangium 
as a dome-shaped structure, which is termed the columella. 
Upon the ripening of the spores the wall of the spore case bursts, 
liberating them. These, falling upon moist nutrient substrata, 
germinate and ultimately form new Rhizopus plants. 
