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..
This is a very pretty plant growing on rotting wood in clusters, often two or three joined at the base, the base of the stem inserted in the rotten wood for 1-2 cm., and the base is clothed with blue, hair-like threads. The plants are 6-9 cm. high, the cap 1-2 cm. broad, and the stem not quite 2 mm. in diameter.
The pileus is ovate to convex, viscid when young. The color is bright blue when young, becoming pale and whitish in age, with a tendency to fuscous on the center. The cap is smooth and the margin finely striate. After the plants have dried the color is nearly uniform ochraceous or tawny. The gills are close, free, narrow, white, then grayish white, the edge finely toothed or fimbriate. The spores are globose, smooth, 6-9 µ. The stem is slender, hollow, faintly purple when young, becoming whitish or flesh color, flexuous, or nearly straight, even, often two united at the base into a root-like extension which enters the rotten wood. The base of the stem is covered with deep blue mycelium which retains its color in age, but disappears on drying after a time. Figure 101 is from plants (No. 2382, C. U. herbarium) collected at Ithaca, in woods, June 16, 1898. Mycena hamatopa Pers. - This is one of the species of Mycena with a red juice which exudes in drops where wounds occur on the plant. It is easily recognized by its dense cespitose habit, the deep blood red juice, the hollow stem, and the crenate or denticulate sterile margin of the cap. Numbers of the plant occur usually in a single cluster, and their bases are closely joined and hairy. The stems are more or less ascending according to the position of the plant on the wood. The plants are 5-10 cm. high, the cap is 1-2.5 cm. broad, and the stem 2-3 mm. in thickness.
Mycena acicula. Cap brilliant red, gills and stem yellowish (natural size). Copyright.
The pileus is conic, then bell-shaped, and as the margin of the cap expands more appears umbonate, obtuse, smooth, even or somewhat striate on the margin. The color varies from whitish to flesh color, or dull red, and appears more or less saturated with a red juice. The thin margin extends a short distance beyond the ends of the gills, and the margin is then beautifully crenate. The gills are adnate, and often extend down on the stem a short distance by a little tooth. The stem is firm, sometimes smooth, sometimes with minute hairs, at the base with long hairs, hollow, in color the same as that of the pileus.
Mycena cyanothrix. Cap viscid when young, blue, becoming pale and whitish in age, and fuscous in center; gills white; stem faintly purple when young, then flesh color or white, blue, clothed with blue hairs at base (natural size). Copyright.
The color varies somewhat, being darker in some plants than in others. In some plants the juice is more abundant and they bleed profusely when wounded, while in other cases there is but little of the juice, sometimes wounds only showing a change in color to a deep red without any free drops exuding. Figure 102 is from plants collected at Ithaca, in August, 1899. It is widely distributed in Europe and North America. Mycena succosa Pk., another species of Mycena with a juice, occurs on very rotten wood in the woods. It is a small plant, dull white at first, but soon spotted with black, and turning black in handling or where bruised, and when dried. Wounds exude a "serum-like juice," and the wounds soon become black. It was described by Peck under Collybia in the 25th Report, p. 74.
Mycena haematopa. Dull red or flesh color, or whitish, a dull red juice exudes where broken or cut, margin of cap serrate with thin sterile flaps (natural size). Copyright.