m, drying quite hard.

The =pileus= is convex to expanded, more or less depressed in the
center, the margin involute, and the surface at first floccose, becoming
in age floccose scaly, since the surface breaks up into triangular
scales more prominent in and near the center, smaller and inconspicuous
toward the margin. The prevailing color is white, but in age the scales
become cream color or buff (in European plants said to become fuscous).
The pileus is either definitely lateral (Fig. 109) or eccentric when the
stem is attached near the center as in Fig. 110. The =gills= are white,
becoming tinged with yellow in age, decurrent (running down on the stem)
in striae for short distances, 4--5 mm. broad, not crowded. The =stem= is
nearly central (Fig. 110), or definitely lateral (Fig. 109), the length
varying according to conditions as stated above. It is firm, tough,
fibrous. The =veil= is prominent in young and medium plants, floccose,
tearing irregularly as the pileus expands.

Figure 110 is from plants (No. 2478a C. U. herbarium) growing from
knothole in living hickory tree, and Fig. 109 from plants (No. 2478b)
growing on a dead stump, near Ithaca.

According to the descriptions of _P. dryinus_ as given by Persoon, and
as followed by Fries and most later writers, the pileus is definitely
lateral, and more or less dimidiate, while in _P. corticatus_ Fr., the
pileus is entire and the stem rather long and eccentric. Stevenson
suggests (p. 166) that corticatus is perhaps too closely allied to
dryinus. The plants in our Fig. 110 agree in all respects with _P.
corticatus_, except that possibly the lamellae do not anastomose on the
stem as they are said to in _corticatus_. According to the usual
descriptions _corticatus_ is given as the larger species, while Fig. 109
of our plant, possessing the typical characters of _dryinus_, is the
larger. The form of the pileus, the length and position of the stem,
depends, as we know, to a large extent on the position of the plant on
the tree. When growing from the upper side, so that there is room above
for the expansion of the cap, the pileus is apt to be more regular, just
as is the case in _Pleurotus ulmarius_, and the stem more nearly
central. When the plant grows from a hollow place in the trunk as those
shown in Fig. 110 did, then there is an opportunity for them to grow
more or less erect, at least until they emerge from the hollow, and then
the pileus is more nearly equal in it