s or asci. These asci are generally
intermixed with slender, empty asci, or sterile cells, called
paraphyses. These asci are variously shaped bodies and are known in
different orders by different names, such as ascoma, apothecium,
perithecium, and receptacle. The Ascomycetes often include among their
numbers fungi ranging in size from microscopic one-celled plants to
quite large and very beautiful specimens. To this group belong the great
number of small fungi producing the various plant diseases.

In a work of this kind especial attention is naturally given to the
order of Discomycetes or cup fungi. This order is very large and is so
called because so many of the plants are cup shaped. These cups vary
greatly in size and form; some are so small that it requires a lens to
examine them; some are saucer-shaped; some are like goblets, and some
resemble beakers of various shapes. The saddle fungi and morels belong
to this order. Here the sac surface is often convoluted, lobed, and
ridged, in order to afford a greater sac-bearing surface.

[Illustration: Figure 4.--Small portion of a section through the
spore-bearing part of a morel in which the spores are produced in little
sacs or asci. (a) An ascus, (b) an ascus discharging its spores, (c) the
spores, (d) sterile cells. Highly magnified.--_Longyear._]

In the mushrooms, puff-balls, etc., we find the spores were borne on the
ends of basidia, usually four spores on each. In this group the spores
are formed in minute club-shaped sacs, known as asci (singular, ascus).
These asci are long, cylindrical sacs, standing side by side,
perpendicular to the fruiting surface. Figure 4 will illustrate their
position together with the sterile cells on the fruiting surface of one
of the morels. They usually have eight spores in each sac or ascus.

The stem of the mushroom is usually in the center of the cap, yet it may
be eccentric or lateral; when it is wanting, the pileus is said to be
sessile. The stem is solid when it is fleshy throughout, or hollow when
it has a central cavity, or stuffed when the interior is filled with
pithy substance. The stems are either fleshy or cartilaginous. When the
former, it is of the same consistency as the pileus. If the latter, its
consistency is always different from the pileus, resembling cartilage.
The stem of the Tricholoma affords a good example of the fleshy stemmed
mushroom, and that of the Marasmius illustrates the cartilaginous.

[Illustra