non common to all free fungous cells.

=The stem.=--The stem is usually fixed to the center of the pileus, but
it may be _eccentric_, i. e., fixed to one side of the center, or
entirely lateral. When the stem is wanting the pileus is _sessile_. With
regard to its interior the stem is _solid_, when it is evenly fleshy
throughout (Fig. 246), or _hollow_ when the interior is occupied by a
cavity (Fig. 248). If the cavity is narrow and tubular the stem is
_fistulose_ (Fig. 245); and if the center is filled with a pithy
substance it is _stuffed_ (Fig. 243). These terms apply only to the
natural condition of the stem, and not the condition brought about by
larvae, which eat out the interior of the stem, causing it to be hollow
or fistulose.

The terms applicable to the consistency of the stem are difficult to
define. In general, stems may be either _fleshy_ or _cartilaginous_. The
meaning of these terms can best be learned by careful study of specimens
of each, but a few general characters can be given here. Fleshy, fibrous
stems occur in the genera _Clitocybe_ and _Tricholoma_, among the
white-spored forms. Their consistency is like that of the pileus,
namely, made up of fleshy, fibrous tissue. They are usually stout,
compared with the size of the plant, and when bent or broken they seem
to be more or less spongy or tough, fibrous, so that they do not snap
readily. Cartilaginous stems have a consistency resembling that of
cartilage. Their texture is always different from that of the pileus,
which is fleshy or membranous. In general such stems are rather slender,
in many genera rather thin, but firm. When bent sufficiently they either
snap suddenly, or break like a green straw, without separating. In
regard to their external appearance some resemble fibrous stems, while
others are smooth and polished as in _Mycena_ and _Omphalia_.

=The veil.=--In the young stages of development the margin of the pileus
lies in close contact with the stipe, the line of separation being
indicated by a kind of furrow which runs around the young button
mushroom. In many genera, as _Collybia_, _Mycena_, _Omphalia_, etc., the
pileus simply expands without having its margin ever united to the stipe
by any special structure, but in other forms, which include by far the
greater number of genera of the _Agaricaceae_ and some _Boleti_, the
interval between the stem and pileus is bridged over by threads growing
from the margin of the pileus and from t