8 THE GENERAL CHARACTERS OF MICROORGANISMS 
of these plants are much alike. But the different species have 
many different methods of reproduction, and it is chiefly upon 
their reproductive bodies that botanists rely to distinguish the 
different species. After the mycelium has grown for a little 
time, it commonly sends up into the air small or large branches 
that produce spores, or reproductive bodies. The method of 
spore production differs sufficiently in the different fungi to 
Fic. 2—Mucor,acommon mold, Fie. 3 —Aspergillus, a common mold, show- 
showing mycelium and spore for- ing mycelium and spore formation 
mation. 
make it possible to classify them. Frequently only the spore- 
producing part of the plant is seen, and it may be the only part 
known, except to botanists. For example, the toadstool is 
only the reproducing portion of a fungus; it has a mycelium 
wholly under ground or buried within the hard mass of the trunk 
of a tree. It is the mycelium, however, that does the work for 
which these fungi are responsible, and not the spore-producing 
part that we see. Figs. 1 to 3 show the general appearance of 
some of these fungi and their methods of forming spores. With these 
methods of reproduction and classification we are not concerned 
in this work, and only such types as are related to our subject 
will be mentioned later in their proper places. 
2. Saccharomyces (Yeasts, Budding Fungi). —These immensely 
important plants are all microscopic in size. While varying 
somewhat, an average size is about 14999 of an inch in diameter. 
They are usually spherical or oval in shape, though sometimes 
