Mycena oregonensis

Description

Mycena oregonensis is a tiny species, with caps only reaching 1 cm (<0.5 in.) in diameter, that is noticeable primarily because of its color. All parts are brilliant yellow and this allows them to stand out in the conifer litter under Douglas-fir and other conifers.

Edibility is unknown, too small to have culinary value.

It is most likely to be confused with a close cousin, Mycena acicula, a species with an orange to the orange-red cap.

Mushroom Identification

1. Cap

   2-8 mm broad, hemispheric becoming convex; margin decurved, slightly undulate; surface moist, faintly pruinose when young, soon glabrous, translucent-striate, indistinctly so when dry; bright yellow, sometimes yellow-orange at the disc, fading to pale yellow or almost white; context thin, yellowish, unchanging; odor and taste mild.

2. Gills

   Adnate to subdecurrent, subdistant, pale yellow, non-marginate.

3. Stem

   1-2.5 cm long, < 1mm thick, fragile, more or less equal; surface pruinose, translucent yellow; veil absent.

4. Spore Print

   White.

5. Habitat

   Solitary to gregarious on rotting conifer needles and leaves of hardwoods, e.g. coast redwood (Sequoia sempervirens), and tanbark oak (Lithocarpus densiflora). Summer to autumn. Rare.

6. Microscopic Features

   Basidia 22-28 x 5-6 µm, slender-clavate, 2-spored, with sterigmata up to 7 µm long. Spores 6.6-9.8 x 3.3-5.5 µm, q = 1.6 - 2.3, qav ~ 1.97, pip-shaped, smooth, non-amyloid. Cheilocystidia 13-68 x 7-17 µm, fusiform, lageniform, utriform, subcylindrical, clavate, with broadly rounded apex, smooth, sometimes with one or two outgrowths, with yellow contents. Pleurocystidia is similar, not frequent. Lamellar trama not vinescent in Melzer's reagent. Hyphae of the pileipellis 2-8 μm wide, covered with simple to furcate, cylindrical, fairly coarse excrescences 2- 15 x 1-4 μm, sometimes the excrescences are cystidia-like, fusiform to lageniform, up to 40 x 8 μm, terminal cells smooth to diverticulate. Hyphae of the cortical layer of the stipe 2-3 µm wide, smooth, terminal cells (caulocystidia) numerous, in tufts, 13-70 x 7-22.5 µm, globose, ellipsoid, fusiform, subcylindrical, with yellow contents. Clamp connections are absent.

Photo sources:

Photo 1 - Author: Arne Aronsen/Naturhistorisk museum, Universitetet i Oslo (CC BY-SA 3.0)

Photo 2 - Author: Sava Krstic (sava) (CC BY-SA 3.0)