The North American Species of Pholiota

145. Pholiota rivulosa sp. nov.

Pileus 2-5 cm latus, convexus, glaber, viscidus, demum rivulosus, cinnamomeus; lamellae pallide luteae, latae, subdistantes; stipes 2-4 cm longus, 3-6 mm crassus, pallidus, deorsum demum subcinnamomeus, sporae 6-7.5 x 3.5-4.2 µ; pleurocystidia 54-78 x 8-12 (15) µ, crassotunicata, anguste fusoide ventricosa. Specimen typicum in Herb. Univ. Mich. conservatum est; legit prope Payette Lakes, Idaho. 6 June 1954. Smith 44318.

Pileus 2-5 cm broad, convex becoming broadly convex, glabrous, viscid to thinly glutinous, dark to pale cinnamon color, the margin near pale pinkish buff, on aging the entire surface rivulose to rimulose but this not showing in the dried specimens. Context thin, pliant, pallid, odor and taste not distinctive.

Lamellae broad, adnate, subdistant, yellowish when young, dingy tawny as spores mature, edges even.

Stipe short, 2-4 cm long, 3-6 mm thick, equal pallid over all at first but soon dingy cinnamon from the base up in age (finally colored to some extent overall), as dried dingy yellowish to pallid over all, veil thin and fibrillose.

Spores 6-7.5 x 3.5-4.2 µ, smooth, apical pore not visible in most spores, shape in face view ovate to elliptic, in profile obscurely inequilateral to subelliptic; color in KOH dull cinnamon, paler in Melzer's sol.; wall less than 0.25 µ thick.

Basidia 4-spored, 17-20 x 6-7 µ, clavate, hyaline in KOH. Pleurocystidia abundant, 54-78 x 8-12 (15) µ, narrowly fusoid-ventricose with a long neck and subacute to obtuse apex, smooth, wall thickened to 1-2 µ in the neck, content yellow in KOH (or hyaline) and typically homogeneous throughout. Cheilocystidia similar to pleurocystidia but smaller (walls often ± 1 µ thick).

Gill trama of a central strand of parallel hyphae with smooth refractive walls up to 0.5 µ thick, the cells elongate and inflated mostly near the septa, pale ochraceous brown to nearly hyaline as revived in KOH; subhymenium a gelatinous layer of hyphae 3-5 µ diam., smooth and hyaline in KOH. Pileus cutis a pellicle of narrow (2-4 µ) hyphae with distinct outlines but in a gelatinous matrix, walls of hyphae incrusted; hypodermium of dull rusty to cinnamon non-gelatinous hyphae smooth or with incrustations. Context of closely arranged yellowish-hyaline (in KOH) hyphae with smooth walls, the cells inflated to 10-15 µ at maturity. Clamp connections present.

Habit, Habitat, and Distribution: Gregarious to caespitose on conifer duff and rotten conifer logs, Pacific Northwest. Type: Smith 44313, type, also 23552, 23526.

Observations: Old specimens are immediately recognizable because of the rivulose pileus, an unusual feature in Pholiota. Young specimens, can be distinguished from P. occidentalis var. occidentalis by the pale yellow gills. P. occidentalis var. luteifolia has pleurocystidia with thinner walls and conspicuous caulocystidia.