Mycetinis scorodonius f. diminutivus R.H. Petersen, K. Dyson & J. Ammirati, f. nov.

Petersen, Ronald H. & Hughes, Karen W., 2017, An investigation on Mycetinis (Euagarics, Basidiomycota), MycoKeys 24, pp. 1-138 : 57-58

11A. Mycetinis scorodonius f. diminutivus R.H. Petersen, K. Dyson & J. Ammirati, f. nov.

Holotype.

United States, Washington, King Co., Bellevue, N47°34'55.91", W122°10'06.96", 4.XI.2015, coll. K. Dyson, KLD 2220-11-4-2015 (TENN69345),

Diagnosis.

1) Basidiomata diminutive (pileus 3-10 mm broad; stipe 10-33 × 0.8-1.5 mm); 2) stipe glabrous-shining, not at all vestured; 3) pileipellis at pileus margin a combination of thick-walled inflated elements and arbuscular pileocystidia; 4) pileipellis over pileus disc a hymeniform layer of inflated hyphal termini, mostly thick-walled and hyaline, with scattered thicker-walled, pigmented individuals; 5) spores 8-9.5 × 3.5-4.5 µm (Lm = 8.65 µm); 6) fruiting on soil or minute plant detritus in urban environments.

Description.

Basidiomata (Fig. 78) diminutive, sparsely gregarious, often cespitose in small groups. Pileus 3-10 mm broad, strongly convex when young with strongly inturned margin, becoming shallowly convex to almost plane by maturity, sometimes shallowly and broadly umbonate, smooth, suede-like (not glabrous), near "sayal brown" 6C5, “cinnamon” 6B5 to “drab” 6D3 over disc, somewhat paler, "ochraceous buff" 5A5, "light grayish olive" 30B2, "tilleul buff" 7B2, "pale pinkish cinnamon" 6A2, over limb and margin, often somewhat radially puckered; margin inrolled when immature, downturned to gently downturned by maturity, entire with no evidence of striation. Lamellae adnexed to adnate, attached to a weak pseudocollarium not seceding with dried lamellae, well-developed (-1 mm broad), hardly ventricose, thickish, total lamellae 52-56, through lamellae 17-22, characteristically crisped when dried, probably off-white when fresh, "cartridge buff" 30A2 to "light buff" 3A2 when dried; lamellulae in 1-2 ranks. Stipe 10-33 × 0.8-1.5 mm, terete, more to less equal, gradually enlarged downward from midsection to base, insititious, glabrous-shining, not at all vestured, apically near "tawny olive" 5C5, downward in midsection "ochraceous tawny " 6C6, downward to base "mummy brown"6F8 to “bister” 5F8. Odor strong, of garlic, but perhaps not all populations; taste not recorded.

Habitat and phenology Fruiting substrate soil with most common over-story trees Pseudotsuga and/or Thuja , probably mulch or minute woody debris; Fall; at this time known only from four collections from urban sites, King Co., Washington.

Pileipellis complex, differing significantly between pileus margin and pileus disc; pileal hairs not observed. Pileipellis of pileus margin a mixture of two elements: 1) inflated elements (Fig. 79 A–D) 12-27 × 7-11 µm overall, with stalk absent to 4-7 × 4-5.5 µm, obscurely clamped, thick-walled (wall -0.8 µm thick, hyaline), delicately roughened, usually producing diverticula apically; diverticula 2-6 × 1-1.5 µm, ranging from bud-like to digitate, usually gnarled and often dichotomous, semi-refringent; and 2) pileocystidia (Fig. 79 E–H) 23-37 ×10– 14 µm overall, arbuscular, stalked (stalk 7-18 × 3-5.5 µm, obscurely clamped), producing a complex of diverticula; diverticula 2-8 × 1.5-2.5 µm, gnarled, often dichotomous, refringent. Pileipellis of pileus disc a mixture of two elements: 1) inflated hyphal termini (Fig. 79 E–H), subglobose, often coarsely dichotomously lobed, thick-walled, smooth or delicately roughened, hyaline, obscurely clamped; and 2) inflated hyphal termini (Fig. 80 A–D), significantly thick-walled (wall -2.0 µm thick along flanks, up to 3 µm thick distally, pigmented yellowish (PhC), smooth; contents dense, pigmented dull ochraceous. Pileus trama loosely interwoven; hyphae 3-7.5(-14) µm diam, firm-walled, often swollen somewhat near branch points, conspicuously clamped. Pleurocystidia (Fig. 81) 29-42 × 7-9 µm, fusiform with acutely rounded apex, conspicuously clamped; contents more or less homogeneous. Basidioles clavate; basidia (Fig. 82) 35-40 × 8-10 µm, elongate-clavate, 4-sterigmate, conspicuously clamped; contents heterogeneous, appearing oily. Basidiospores (Fig. 83) (7.5-)8-9.5(-10) × 3.5-4.5(-5) µm (Q = 1.89-2.29; Qm = 2.12; Lm = 8.65 µm), ellipsoid to narrowly subamygdaliform, hyaline, thin-walled, inamyloid; contents heterogeneous, multigranular or multiguttulate. Lamellar edge probably sterile; cheilocystidia (Fig. 84) plentiful, 23-35 × 6.5-11 µm overall, stalked (stalk 8-20 × 3.5-4.5 µm, obscurely clamped), swollen distally, thick-walled (wall -0.7 µm thick, hyaline), surmounted by a cluster of diverticula; diverticula stiff, rigid, gnarled, often branching, usually dichotomously. Stipe medullary hyphae 3.5-8.5 µm diam, firm- to thick-walled (wall -0.5 µm thick, hyaline), strictly parallel, free (not involved in slime matrix), conspicuously clamped. Stipe cortical hyphae 2-5.5 µm diam, thick-walled (wall -1.0 µm thick, weakly pigmented), obscurely clamped. Caulocystidia absent.

Commentary.

Pileipellis in My. scorodonius f. diminutivus is complex. Elements of pileus margin differ substantially from those of the pilus disc. This complexity is similar to that seen in My. opacus and My. scorodonius , both of which form pileocystidia at or near the pileus margin, and suppress them over the pileus disc. The occasional occurrence of very thick-walled, pigmented inflated individuals in the pileus disc is typical of the genus.

A non-vestured stipe is not typical of Mycetinis taxa. Mycetinis cinnamomeus from South Australia exhibits basidiomata of similar size; Cleland’s description does not include vesture and Desjardin’s notes on the type specimen indicates absence of caulocystidia. Mycetinis scorodonius also exhibits a glabrous-shining stipe, which may be reflected in ITS sequences from f. diminutivus, also without stipe vesture, which match those of My. scorodonius . Basidiomatal dimensions are significantly different, however, raising the question of molecular versus morphological evidence. This situation also arises with My. salalis / My. copelandii (q.v.).

All listed collections of f. diminutivus were made in mulched planters near office buildings, from which plant debris was regularly removed. Paucity of substrate, perhaps exacerbated by urban environment (i.e. lack of water, aerial pollution, frequent harsh sunlight, mulch pH, etc.) may be causative factors in the production of diminutive basidiomata.

Specimens examined.

United States, Washington, King Co., Bellevue, N47°34'55.91", W122°10'06.96", 4.XI.2015, coll. K. Dyson, KLD 2220-11-4-2015 (TENN69345 (holotype); same data, KLD 22218-11-4-2015 (TENN69348); same location, 14.X.2015, coll. K.L. Dyson, KLD 22167-10-14-2015 (TENN69347); Redmond, N47°37'56.04", W122°07'59.56", 20.X.2015, coll. K.L. Dyson, KLD 19061-10-20-2015 (TENN69346).