This section is from the book "Studies of American Fungi: Mushrooms, Edible, Poisonous, Etc.", by George Francis Atkinson. Also available from Amazon: Studies of American Fungi: Mushrooms, Edible, Poisonous, Etc..
In the genus Collybia the annulus and volva are both wanting, the spores are white, the gills are free or notched, or sinuate. The stem is either entirely cartilaginous or has a cartilaginous rind, while the central portion of the stem is fibrous, or fleshy, stuffed or fistulose. The pileus is fleshy and when the plants are young the margin of the pileus is incurved or inrolled, i. e., it does not lie straight against the stem as in Mycena.
Many of the species of Collybia are quite firm and will revive somewhat after drying when moistened, but they are not coriaceous as in Marasmius, nor do they revive so thoroughly. It is difficult, however, to draw the line between the two genera. Twenty-five of the New York species of Collybia are described by Peck in the 49th Report N. Y. State Mus., p. 32 et seq. Morgan describes twelve species in Jour. Cinn. Soc. Nat. Hist., 6: 70-73.
Collybia radicata Rehl. Edible. - This is one of the common and widely distributed species of the genus. It occurs on the ground in the woods or groves or borders of woods. It is quite easily recognized by the more or less flattened cap, the long striate stem somewhat enlarged below and then tapering off into a long, slender root-like process in the ground. It is from this "rooting" character that the plant gets its specific name. It is 10-20 cm. high, the cap 3-7 cm. broad, and the stem 4-8 mm. in thickness.
The pileus is fleshy, thin, convex to nearly plane, or even with the margin upturned in old plants, and the center sometimes umbonate. It is smooth, viscid when moist, and often with wrinkles on the surface which extend radially. The color varies from nearly white in some small specimens to grayish, grayish brown or umber. They flesh is white. The gills are white, broad, rather distant, adnexed, i. e., joined to the stem by the upper angle. The spores are elliptical and about 15x10 µ. The stem is the same color as the pileus though paler, and usually white above, tapers gradually above, is often striate or grooved, or sometimes only mealy. The long tapering "root" is often attached to some underground dead root. Fig. 94 is from plants (No. 5641, C. U. herbarium) collected at Ithaca, August, 1900.
Collybia velutipes Curt. Edible. - This is very common in woods or groves during the autumn, on dead limbs or trunks, or from dead places in living ones. The plants are very viscid, and the stem, except in young plants, is velvety hairy with dark hairs. Figure 95 is from plants (No. 5430, C. U. herbarium) collected at Ithaca, October, 1900.
Plate 30, Figure.93. - Clitocybe multiceps. Plants white or gray to buff or grayish brown. (Three-fourths natural size.) Copyright.
Plate 31, Fig 94
Collybia radicata. Caps grayish-brown to grayish and white in some small forms. (Natural size.) Copyright.
Plate 32, Fig 95
Collybia velutipes. Cap yellowish or reddish yellow, viscid, gills white, stem dark brown, velvety hairy (natural size). Copyright.
Collybia loagipes Bull., is a closely related plant. It is much larger, has a velvety, to hairy, stem, and a much longer root-like process to the stem. It has been sometimes considered to be merely a variety of C. radicata, and may be only a large form of that species. I have found a few specimens in the Adirondack mountains, and one in the Blue Ridge mountains, which seem to belong to this species.
Collybia platyphylla Fr. Edible. - This is a much larger and stouter plant than Collybia radicata, though it is not so tall as the larger specimens of that species. It occurs on rotten logs or on the ground about rotten logs and stumps in the woods from June to September. It is 8-12 cm. high, the cap 10-15 cm. broad, and the stem about 2 cm. in thickness.
The pileus is convex becoming expanded, plane, and even the margin upturned in age. It is whitish, varying to grayish brown or dark brown, the center sometimes darker than the margin, as is usual in many plants. The surface of the pileus is often marked in radiating streaks by fine dark hairs. The gills are white, very broad, adnexed, and usually deeply and broadly notched next the stem. In age they are more or less broken and cracked. The spores are white, elliptical, 7-10x6-7µ.
The plant resembles somewhat certain species of Tricholoma and care should be used in selecting it in order to avoid the suspected species of Tricholoma.