Cortinarius is from cortina, a curtain, alluding to a cobwebby veil seen only in the comparatively young plants. Sometimes, parts of it will seem more substantial, remaining for a time on the margin of the cap or on the stem. The color of the pileus varies and its flesh and that of the stem are continuous. The hymenophore and the gills are continuous. The gills are attached to the stem, frequently notched, membranaceous, persistent, changing color, dry, powdery, with rusty-yellow spores which drop slowly. The veil and gills are the chief marks of distinction. The former is gossamer-like and separate from the cuticle, and the latter are always powdered. It is always essential to note the color of the gills in the young plant, since color is variable and sometimes shows only the slightest trace on the stem, colored from the falling spores.
Most authorities divide the genus into six tribes, from the appearance of the pileus. They are as follows:
I. Phlegmacium, meaning a shiny or clammy moisture. The pileus has a continuous pellicle, viscid when moist, stem dry, veil spider-webby.
II. Myxacium, meaning mucus, slime; so called from the glutinous veil. The pileus is fleshy, glutinous, rather thin; the gills are attached to the stem, slightly decurrent; the stem is viscid, polished when dry, slightly bulbous.
III. Inoloma, meaning a fibrous fringe; from is, genitive inos, a fibre; and loma, a fringe.
The pileus is fleshy, dry, not hygrophanous or viscid, silky with innate scales; the gills may be violaceous, pinkish-brown, yellow at first, then in all cases cinnamon-color from the spores; the stem is fleshy and somewhat bulbous; veil simple.
IV. Dermocybe, meaning a skinhead; from derma, skin, and cybe, a head.
The pileus thin and fleshy, entirely dry, at first clothed with silky down, becoming smooth in mature plants. The gills are changeable in color. The stem is equal or tapering downward, stuffed, sometimes hollow, smooth.
V. Telamonia, meaning a bandage or lint. The pileus is moist, watery, smooth or sprinkled with whitish superficial fibres, the remnants of the web-like veil. The flesh is thin, somewhat thicker at the center. The stem is ringed and frequently scaly from the universal veil, slightly veiled at the apex, hence almost with a double veil. The plants are usually quite large.
VI. Hydrocybe, meaning water-head or moist head. The pileus is moist, not viscid, smooth or sprinkled with a whitish superficial fibril, flesh changing color when dry, and rather thin. The stem is somewhat rigid and bare. Veil thin, fibrillose, rarely forming a ring. Gills also thin.