(umbonate). It may be covered with warts, marked with lines (striate),
or zoned with circles. The margin may be acute or obtuse, rolled
backward or upward (revolute), or rolled inward (involute); it may be
thick or thin.


THE STEM.

The stem is the stalk that supports the cap. It is sometimes attached to
one side, and then it is said to be lateral or between the centre and
side, and it is called eccentric; when it is in the middle, or nearly
so, it is central.

It is either solid, fleshy, stuffed with pith, or hollow, fibrous, firm
and tough (cartilaginous). It is often brittle and breaks easily, or it
will not divide evenly in breaking. Its color and size both vary, like
the cap. It may taper toward the base, or toward the apex, be even or
cylindrical. Its surface may be smooth (glabrous), covered with scales
(squamulose), rough (scabrous), dotted, lacerated, or be marked with a
network of veins (reticulated). The base may be bulbous, or only swollen
(incrassated), and it may root in the ground.

[Illustration: Sections of gill bearing mushrooms.

Gills adnexed
Gills free
Gills adnate
Gills decurrent
Gills sinuous
Gills serrated