The North American Species of Pholiota
19. Pholiota minutula sp. nov.
Illustrations: Text figs. 26-27.
Pileus 2-6 mm latus, convexus, siccus, fibrillosus, sordide ochraceobrunneus. Lamellae latae, confertae, vel subdistantes, argillaceae demum fulvae. Stipes 2-3.5(4) mm longus, -1 mm latus, fibrillosus. Vellum luteobrunneum. Sporae 7-9 x 5-6 µ, subtruncatae. Pleurocystidia desunt. Cheilocystidia 26-40 x 4-7 µ, anguste clavata vel subfilamentosa. Specimen typicum in Herb. Univ. Mich. conservatum est; legit prope Dexter, Mich. 5 Oct. 1944, Smith n. 34229.
Pileus 2-6 mm broad, convex becoming broadly convex, surface dry and densely fibrillose, the fibrils fringing the margin for a time after the veil breaks, dingy yellow-brown fresh, drying dingy clay-color.
Lamellae broad, close to subdistant, adnate or with a decurrent tooth, dingy tan becoming dull rusty brown, edges slightly crenulate.
Stipe 2-3.5 (4) mm long, less than 1 mm thick, shaggy-fibrillose from veil fibrils and colored about like the pileus, apex pruinose.
Spores rusty cinnamon in KOH under the microscope, 7-9 x 5-6 µ, wall up to 0.5 µ thick, smooth, elliptic to ovate in face view, elliptic to obscurely inequilateral in profile, with a distinct apical pore causing apex to appear slightly truncate in large spores.
Basidia 24-30 x 6-7.5 µ, 4-spored, hyaline in KOH, clamped at base. Pleurocystidia none. Cheilocystidia 26-40 x 4-7 µ, flexuous-filamentous to narrowly clavate or near base slightly ventricose, thin-walled, smooth, hyaline or ochraceous in KOH. Pileus cutis of appressed non-gelatinous tubular hyphae 2-5 µ diam., ochraceous in KOH and with tawny incrustations arranged in a variable pattern. Context hyphae mostly hyaline to yellow in KOH and thin-walled. Clamp connections present. All hyphae inamyloid.
Habit, Habitat, and Distribution: Scattered on bark of living cottonwood tree, Dexter, Mich., Oct. 5, 1949, Smith 34229, type.
Observations: This is a shaggy little species about the size of Mycena corticola but with different spores. It differs from Naucoria horizontalis in smaller spores (14-18 x 6-7 µ for the latter). It differs from P. corticola in lacking pleurocystidia and in having the well developed germ pore at the spore apex. The color of the spores is about that of P. aberrans but the wall is not quite as thick. This species is one of the reasons for not recognizing the genus Pachylepyrium. It has the spore features of that genus but, as Pholiota species have evolved, it is in a different line.