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 genus, with ferruginous spores, corresponds with Collybia among the white-spored agarics. The gills are free or attached, but not decurrent, and the stem is cartilaginous. The plants grow both on the ground and on wood. Peck, 23rd Report N. Y. State Mus., p. 91, et seq., gives a synopsis of seven species.
Naucoria semi=Norbicularis Bull. Edible. - This is one of the common and widely distributed species. It occurs in lawns, pastures, roadsides, etc., in waste places, from June to autumn, being more abundant in rainy weather. The plants are 7-10 cm. high, the cap 3-5 cm. broad, and the stem 2-3 mm. in thickness. The pileus is convex to expanded, and is remarkably hemispherical, from which the species takes the name of semi-orbicularis. It is smooth, viscid when moist, tawny, and in age ochraceous, sometimes the surface is cracked into areas. The gills are attached, sometimes notched, crowded, much broader than the thickness of the pileus, pale, then reddish brown. The stem is tough, slender, smooth, even, pale reddish brown, shining, stuffed with a whitish pith. Peck says that the plants have an oily flavor resembling beechnuts.
Naucoria vernalis was described by Peck in 23rd Report N. Y. State Mus., p. 91, from plants collected in May. The plants described here appeared in woods in late autumn. The specimens from which this description is drawn were found growing from the under side of a very rotten beech log, usually from deep crevices in the log, so that only the pileus is visible or exposed well to the view. The plants are 4-8 cm. high, the cap 2-3 cm. broad, and the stem 4-5 mm. in thickness. The taste is bitter.
Naucoria vernalis. Cap hair brown to clay color; gills grayish brown to wood brown; stem clay color (natural size). Copyright.
The pileus is convex, then the center is nearly or quite expanded, the margin at first inrolled and never fully expanded, hygrophanous, smooth (not striate nor rugose), flesh about 5-6 mm. thick at center, thin toward the margin. The color changes during growth, it is from ochraceous rufus when young (1-2 mm. broad), then clove brown to hair brown and clay color in age. The gills are grayish brown to wood brown, at first adnate to slightly sinuate, then easily breaking away and appearing adnexed. The spores are wood brown in color, oval to short elliptical and inequilateral 6-8 x 4-5 µ. Cystidia hyaline, bottle shaped, 40-50 x 8-12 µ. The stem is somewhat hollow and stuffed, rather cartilaginous, though somewhat brittle, especially when very damp, breaking out from the pileus easily though with fragments of the gills remaining attached, not strongly continuous with the substance of the pileus. The color is buff to pale clay color; the stem being even, not bulbous but somewhat enlarged below, mealy over the entire length, which may be washed off by rains, striate at apex either from marks left by the gills or remnants of the gills as they become freed from the stem. Base of stem sometimes with white cottony threads, especially in damp situations. In the original description the stem is said to be "striate sulcate." Figure 150 is from plants (No. 3242, C. U. herbarium) collected in woods near Ithaca, October 1, 1899.