FUNGI AND FUNGOUS DISEASES OF PLANTS 237 
Under magnification the hyphe may be seen to consist of 
heavy, tubular cell walls, in which the granular protoplasm is 
not separated into distinct cellular divisions by transverse 
walls, as it is in most of the alge. 
Bread mold lives upon and within its nutrient substance 
anil absorbs food material directly from it. Parts that are in 
contact with the sub-stratum do the work of food absorption. 
Food is carried through the tubular cells to the parts of the 
mycelium that are above the food material. Since nutrient 
material is secured in ready and abundant supplies, the growth 
and extension of the mold is usually quite rapid. 
224. Effect of mold upon bread. If a piece of bread upon 
which mold is growing vigorously is kept moist, much of the 
bread is consumed by the mold, but usually the mold will not 
continue to grow until the bread is completely consumed. 
Either because it has secured all the food it can extract from 
the bread, or because it has secreted substances that prevent 
its further growth, or because it is unable to hold its own 
with other organisms (molds and bacteria), the bread mold 
after a time ceases to grow. Other molds and bacteria may 
appear, one kind following another for weeks, until the decay 
of the bread is almost or quite complete. 
If the mold, and the material upon which it grows, is kept 
tightly sealed, growth stops before all the food material is 
used. Molds often grow for a time in jars of fruit, forming 
upon the top of the fruit a coating which remains until the 
jar is opened. If this coating is removed and a fresh supply 
of air is admitted, a new growth soon appears, and if a con- 
stant supply of air is maintained, various molds may grow 
until all the fruit is destroyed. 
225. Reproduction of bread mold. In addition to vegetative 
reproduction by means of stolons, this mold also reproduces 
itself both asexually and sexually. Upon the ends of upright 
hyphe, sporangia are produced (fig. 184). In the develop- 
ment of the sporangia, first a transverse wall cuts off a small 
tip of the upright stalk. This tip cell grows rapidly until it 
