North American species of Mycena.

176 NORTH AMERICAN SPECIES OF MYCENA

79. MYCENA AURANTIIDISCA Murrill
Mycologia, 8: 220. 1916
Prunulus aurantiidiscus Murrill, North Am. Flora, 9: 336. 1916.
Illustrations: Text fig. 17, nos. 6, 8 (p. 173).
Pileus 7-20 mm. broad, obtusely conic when young, not expanding
or becoming merely broadly conic, margin appressed against the stipe
when young, flaring somewhat in age, striate when moist, glabrous,
"mikado orange" when young and fresh, fading to "mustard yellow"
on the disc and whitish along the margin; flesh thin and fragile, orange
or yellow, odor and taste mild; lamellae bluntly adnate to slightly
hooked, close to subdistant, 20-24 reach the stipe, narrow to subventricose, white at first, becoming tinged yellowish in age, margin
concolorous with the faces; stipe 2-3 cm. long, 1 mm. thick, equal,
strict, hollow, fragile, surface faintly pruinose above, scarcely fibrillose
at the base, upper portion white, basal portion yellowish.
Spores ellipsoid, 7-8 X 3.5-4 A, nonaimyloid; basidia four-spored.
20 X 6 p; cheilocystidia and pleurocystidia similar, 4,, o -,
fusoid with a long narrow neck, smooth in mounts of fresh material,
frequently having the apex or the neck incrusted with an amorphous
mass in mounts of revived material, hyaline; pileus trama with a
poorly differentiated pellicle, the tissue beneath it homogeneous or the
upper portion composed of only slightly enlarged hyphae, faintly
vinaceous brown in iodine.
Habit, habitat, and distribution.-Gregarious under Douglas fir
and pine during the spring and fall; Idaho, Washington, and Oregon.
Not common.
Material studied.-Smith, 7750, 7778, 7880, 7932, 8239, 8415,
8928, 9305, 14641, 16463, 16507. Slipp, UIFP: 3249.
Observations.-It remains an open question whether M. aurantiidisca is a distinct species or merely a form of M. adonis. The
difference in the color of the young stages is striking, but no more so
than that of the two forms of M. flavoalba. In fact, there actually is
less difference. The young stages of M. adonis are scarlet, whereas
those of M. aurantiidisca are brilliant orange. The latter fades to
whitish, at least on the margin, and the former to yellow, but both
are characterized by dominantly yellow colors when first reaching
maturity.