360 THALLOPHYTES 
True Molds (Mucorales). — There are a number of Molds 
some of which belong to other divisions of the Fungi. The 
Molds of this order are characterized by a zygosporic reproduc- 
tion, on which account they are called Zygomycetes. Of the 
nearly 200 species known, Bread Mold is the most familiar one. 
Fic. 311. — Conidia of the Late Blight of the Potato developing zodspores, 
and zoéspores growing hyphae. X about 400. After Ward. 
Bread Mold (Rhizopus nigricans). — Bread Mold is very 
common about homes, producing a fluffy tangle of hyphae on the 
surface of bread, fruit, and other favorable nutrient substances 
when left exposed (Fig. 313). It is sometimes injurious to 
Sweet Potatoes and other vegetables in storage. The fluffy 
tangle of hyphae is white while young but becomes dark when old, 
owing to the dark color of the mature sporangia. 
A strong poison has been found in connection with Rhizopus 
nigricans, and it has been suggested that some of the diseases of 
stock, such as the “ cornstalk disease”’ and the “‘ horse disease,” 
prevalent in some of the Western states, may be due to the toxin 
which stock get in moldy fodder or other feed. The toxin 
apparently is only effective when introduced into the circulatory 
system. This is shown by the fact that rabbits can be fed the 
Mold without any injury, but when a little of the sap is expressed 
from the mycelium and injected into the blood, the animal dies 
almost instantly. 
The mycelium consists of numerous coenocytic branching 
hyphae. Some of the hyphae penetrate the substratum and 
gather food, while others grow above the substratum and produce 
the visible fluffy mass. The surface hyphae with more or less 
