Führ. Pilzk.: 108. 1871.
Common Name: none
Synonym: Mycena fusco-ocula A.H. Smith
Cap 5-20 (25) mm obtuse-conic, broadly so to campanulate in age, often with a low umbo; margin decurved, sometimes becoming upturned and crenate; surface moist, translucent-striate to somewhat sulcate, hygrophanous, when fresh, dark greyish-brown with a faint whitish bloom at the disc, margin paler, fading overall in age; context thin, soft, approximately 1 mm thick, white to grey; odor and taste not distinctive.
Gills close to subdistant, ascending-adnate, occasionally with a decurrent tooth, narrow, up to 2 mm in width, edges and faces concolorous; lamellulae in 2-3 series.
Stipe 40-75 (100) x 1-2 mm in width, slender, cylindrical, hollow, fragile, equal to slightly larger at the base; surface glabrous to finely pruinose at apex, greyish brown, usually paler above, whitish hairs at base occasionally extending up the stipe; partial veil absent; fresh specimens producing a white milky juice when injured or cut, particularly at the base.
Spores 9-13 x 5-6 µm, smooth, thin-walled, ellipsoid in face-view, tear-shaped in profile with a well-developed hilar appendage, amyloid; spores white in deposit.
Scattered or forming large groups in litter of conifers and hardwoods; especially common under coast redwood (Sequoia sempervirens); also reported from low elevations of the Sierra Nevada; fruiting from late fall to mid-winter along the coast and late fall in the Sierra Nevada; common in most years.
Edibility unknown; insignificant.
California is home to many greyish-brown Mycenas, most of which are difficult to identify without a microscope. Mycena galopus is an exception. It is the only known Mycena in California that exudes a milky juice when tissues such as the base of the stipe are cut or injured. Unfortunately, this feature may be faint or absent in older specimens. Lacking milky juice, a helpful macroscopic character is a bicolored cap, dark at the disk, shading to a pale margin. Interestingly, the contrasting cap colors are the basis of the species epithet for a synonym of Myena galopus, i.e. Mycena fusco-ocula. Mycena galopus is a cosmopolitan species, found not only along the Pacific Coast, but also in the eastern US, Europe, and Japan.
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