Marasmius: white spores; collybioid stature; pileus bald or not fibrillose; stipe insititious, often wire-like or black and hair-like; often with rhizomorphs; often with a strong onion-like or garlic-odor; fruiting bodies not viscid or gelatinous. Collybia and Mycena can be separated by the non-insititious stipe, lack of strong onion-like or garlic-like odor. Habitat: terrestrial, on leaves of hardwood plants, on needles of Conifers, often on bark, rarely on wood. Omphalina and its segregate genera can be separated by their omphalinoid stature.

Typically species of Marasmius do not grow on cones. In addition, the stipe base is typically unicolorous; species with a pale apex and a brown, dark-brown, or black stipe base most often belong to Marasmiellus. Species of Micromphale grow on Madrone bark or Coast Redwood branchelets and are not wiry or hair-like. Species of Baeospora and Strobilurus are found on cones. Crinipellis piceae grows on spruce needles and has a fibrillose pileus.

Genera which have been segregated out of Marasmius and are acceptable for Botany 360 are:

Micromphale: there are typically 2 species of Micromphale in northern California, one grows on madrone bark and the other on coast redwood branchlets. M. arbuticola which grows on the scale bark of Madrone and M. sequoiae which grows on the branches of coast Redwood. Both species have a dark brown or greyish orange, minutely pruniose or pubescent, insititious stipe, a rugulose to rugulose-sulcate stipe, and either a onion-like odor in M. arbuticola and no odor in M. sequoiae. Species of Marasmius also grow on Madrone or Coast Redwood, but these have a black, hair-like stipe, blackish rhizomorphs attached to the stipe base, and/or a strong garlic-like odor.

Marasmiellus: Typically recognized by its insititious, pruinose stipe; in two of the three species the stipe apex is pale and the stipe base is either brown or black and in all 3 species the stipe is not wiry nor black and wire-like and the odor is at most mildly onion-like or garlic-like. All species grow on conifer needles which in two species have a 3 species of Marasiellus occur in northern California; M. candidus which grows in great abundance in coastal forests and has a white, rugulose-sulcate pileus, distant and intervenose gills, a pubescent stipe with a white apex and dark base; M. filopes (rare in California) has a minute (1-2 mm broad), pinkish buff or pale brownish grey pileus, pruinose stipe insitition on needles of conifers, and by the mild garlic odor; and M. pluvius has a insititious, pruinose stipe with a pallid apex and reddish-brown base, grows on needles of conifers, and has a mild odor and taste.

Crinipellis

Baeospora

Stobilurus.