The North American Species of Pholiota

55. Pholiota populicola sp. nov.

Illustrations: Text figs. 155-156.

Pileus 1.5-3.5 (4) cm latus, convexus deinde planus, "argus brown," denique margine "ochraceous tawny," denique "light buff," viscidus, glaber, striatulatus. Caro concolor; odore et gustu mitis. Lamellae depresso-adnatae, mox secedentes, stipatae," "tilleul buff," deinde "ochraceous tawny," planae vel leviter crenulatae. Stipes 7-9 cm longus, 3-4 mm crassus, supra albidus, ab imo sursum "Dresden-brown," pallido-coriaceus, conferte fibrillosus. Velum faciens crassum, superiorem, pallidum, xylinum annulum. Sporae 5-7 x 4.5-4.8 x 4-4.5 µ, leves, truncatae, subcompressae. Pleurocystidia desunt; cheilocystidia 20-27 x 3-7 µ, ventricosa vel ventricoso-rostrata. Cuticula gelatinosa. Specimen typicum in Herb. Univ. Mich. conservatum est; lectum prope Clearwater River, Olympic Peninsula, Washington, May 9, 1939. Smith 13260.

Pileus 1.5-3.5 (4) cm broad, convex becoming plane, at first "argus brown" over all, becoming "ochraceous tawny" on the margin, fading to "light buff" and finally dingy tawny, viscid when young, glabrous, striatulate. Context thin, concolorous with surface; odor and taste not distinctive.

Lamellae depressed adnate and soon seceding, crowded, more or less 30 reach the stipe, narrow (3-4 mm), 2-3 tiers of lamellulae, pallid ("tilleul-buff"), becoming "ochraceous-tawny," edges very thin and even to slightly crenulate.

Stipe 7-9 cm long, 3-4 mm thick, whitish above, becoming "Dresden-brown" from the base upward, tubular equal or slightly enlarged downward, at first densely fibrillose with a pale buff fibrillose coating, fibrillose-squamulose above the annulus, generally glabrescent. Annulus thick, superior, pallid, and striate above, cottony and at times darker below, often evanescent.

Spores 5-7 x 4.5-4.8 x 4-4.5 µ smooth, distinctly truncate (truncation up to 1.5 µ broad), broadly ovate to elliptic-truncate in face view obscurely inequilateral to subelliptic in profile, pale cinnamon to pale tawny in KOH, paler in Melzer's reagent than in KOH, wall relatively thin (estimated at less than 0.25 µ).

Basidia 17-22 x 5-6 µ, narrowly clavate to subcylindric, 4-spored, hyaline to yellowish in KOH and Melzer's sol. Pleurocystidia none. Cheilocystidia 20-27 x 3-7 µ, ventricose-rostrate but small, varying to merely fusoid-ventricose or with odd shapes but apex obtuse, thin-walled, hyaline in KOH and Melzer's reagent, smooth, content homogeneous. Caulocystidia none located.

Gill trama of subparallel non-gelatinous hyphae with broad short to elongate cells, walls hyaline to yellowish in KOH and Melzer's reagent, and showing only a slight tendency to thickening (typically thin-walled); subhymenium narrow and indistinct. Pileus cutis a gelatinous layer of smooth hyaline hyphae 2-4 µ diam. appressed and the layer up to 8-12 hyphae deep (but usually thinner as seen in revived material); hypodermial region of yellowish to hyaline hyphae which are nongelatinous and cells distinctly inflated, the hyphal walls thin to slightly thickened but not measurable (less than 0.4 µ), yellowish in Melzer's reagent. Context hyphae yellowish to nearly hyaline in KOH and in Melzer's reagent; oleiferous hyphae rare. Clamp connections present.

Habit, Habitat, and Distribution: On rotten logs of Populus trichocarpa, Clearwater River, Olympic Mountains, Washington, May 9, 1939, Smith 13260 type.

Observations: The thick, superior, striate annulus collapses and disappears, but when present it is quite distinct from that of P. vernalis. The stipe below the annulus is not squamulose with recurved squamules as in P. mutabilis but rather is coated with pale buff veil fibrils or these aggregating into patches. These differences in addition to the habitat distinguish the species from P. mutabilis, but the aspect of the dried basidiocarps of these two is very similar.