Mycetinis olidus (Gilliam) R.H. Petersen, comb. nov.

Petersen, Ronald H. & Hughes, Karen W., 2017, An investigation on Mycetinis (Euagarics, Basidiomycota), MycoKeys 24, pp. 1-138 : 31-35

7. Mycetinis olidus (Gilliam) R.H. Petersen, comb. nov.

Marasmius olidus Basionym. Gilliam 1975. Mycologia 67: 822. ≡ Marasmius copelandii var. olidus (Gilliam) Desjardin 1987a. Mycologia 79: 129.

Holotype.

United States, Michigan, Oakland Co., Proud Lake [N42°33'42", W83°31'43"], 1.XI.1970, coll W.W. Patrick, Gilliam 997, (MICH).

Diagnosis.

1) Basidiomata diminutive (pileus 3-18 mm broad; stipe 12-31 × 0.4-2.1 mm; 2) vestured, grayish brown stipe; 3) curved-clavate spores 10-16 µm long; 3) fruiting habitat on fallen Pinus needles and Quercus leaves; 4) penetrating odor of garlic; 5) distribution in eastern United States from Michigan to Tennessee and North Carolina, south to central Florida.

Pileus 3-18 mm broad, pulvinate or convex at first, then plano-convex and often umbilicate, finally plane or convex with a wavy margin, dry, dull, opaque or matt, minutely velutinous particularly on the disc; margin entire to sulcate-striate nearly to disc, pliant, reviving; disc moderate brown in primordia, soon light yellowish brown (Maerz & Paul 11D4-5), "grayish olive" 30C3 outward "pale olive buff" 3B2, often tinged pink, or moderate brown on the disc and light yellowish brown elsewhere. Pileus trama thin (-1.5 mm thick), firm, yellowish white. Lamellae distant, adnexed or subdecurrent, narrow (0.6-1.5 mm broad), thin, distant, moderately numerous (through lamellae 15-20), unequal, with 2-3 irregular tiers of lamellulae, sometimes seceding in age, membranous, often subventricose, entire or minutely fimbriate, straight, occasionally somewhat intervenose, rarely forked near the stipe, light yellowish brown (M&P 11B4) to "tilleul buff" 7B2, in drying becoming concolorous with mature pilei to distinctly “cinnamon” 6B5 or avellaneous (?necropigment). Stipe 12-31(-35) mm long, 0.5-2.1 mm thick, central, terete or flattened at the apex, tapered slightly to the base, straight or curved, dry, dull, opaque, hollow, cartilaginous, even, pruinose above, tomentose below, concolorous with lamellae, yellowish white or light yellowish brown up to 2 mm from the apex downward, moderate brown, grayish brown tinged pink, "wood brown" 7C4 to "buffy brown"6D4 or blackish brown below; not insititious; vesture whitish at stipe apex, downward brownish pink. Sterile stipes occasionally present along the leaf veins near basidiomata, tapered, glabrous, yellowish brown. Rhizomorphs lacking or rare, extremely slender (0.1-0.3 mm broad), -8 mm long, curly, unbranched, black. Basal mycelium on hardwood leaves sometimes forming a flat disc, often visible near the leaf veins as well, fine, resembling spun glass, white. Odor weakly pleasant to pungent, of garlic. Taste of garlic or onion, often persisting in drying and storage.

Habitat and phenology.

Gregarious on duff of Pinus strobus and P. resinosus and on midribs of hardwood leaves, usually Quercus (teste Gilliam 1975); eastern North America from Ontario/Quebec south to Gulf Coast; May to November.

Pileipellis constructed of three interlocking types of structures: 1) pileal hairs (Fig. 41) as side-branches of repent pileipellis, -75 × 4-8(-14) µm, thin- to firm-walled, minutely roughened (perhaps resinous), usually subcapitulate; 2) inflated hyphal termini (Fig. 42) broadly clavate, subglobose, to spheropedunculate, (9-)20-36(-42) × (4-)11-21)-24) µm, usually thick-walled (wall -1.0 µm thick, occasionally weakly pigmented), occasionally with lobose apical outgrowths; and 3) free-form hyphal segments (Fig. 43), often quite extensive, firm-walled, with lobes and extended arms, occasionally internally septate, sometimes with internal clamp connections. Pileus and lamellar tramae loosely interwoven; hyphae 3-7.5 diam, thin-walled, occasionally clamped. Pleurocystidia (Fig. 44) 14-32 × 6.5-8.5 µm, generally fusiform with rounded apex, conspicuously clamped; contents more or less homogeneous. Basidia (Fig. 45) 19-26(-29) × (4-)7-10 µm, clavate, hardly capitulate, 4-sterigmate, obscurely clamped; contents heterogeneous, multiguttulate; sterigmata slender, spindly. Basidiospores (Fig. 49A) (8-)11-16 × (2.8-)3.5-4(-4.5) µm (Q = 2.00-3.67; Qm = 2.93; Lm = 11.7 µm), marasmioid (distally rounded, proximally tapered), thin-walled, inamyloid; contents minutely granular. Cheilocystidia (Figs 46, 47) rare to plentiful, occasionally probably rendering lamellar edge sterile, 28-45 × 10-16 µm (at widest point), stalked (stalk 5-30 × 3.5-5 µm, obscurely clamped), expanded distally, ranging in shape from obpyriform, to obpyriform with one or more large lobes or digitate diverticula, hyaline, thin- to firm-walled; contents more or less homogeneous. Stipe medullary hyphae 3-9 µm diam, strictly parallel, nonamyloid, thin-walled. Stipe cortical hyphae 2-8.5 µm diam, nonamyloid, thick-walled (wall -2 µm thick, pigmented pale yellow to moderate reddish brown, immediately weakly yellow-olive in 3% KOH (BF). Caulocystidia (Figs 48, 49B) -150 × 2.5-8.5 µm, arising as side branches or termini of stipe surface hyphae, thick-walled (wall - 2.5 µm thick, hyaline to moderate brown, light olive green in KOH), scattered on stipe apex, downward more densely gregarious, toward stipe base gathering into synemmatoid columns of -150 individuals, appearing hirsute; stipe base strigose.

Commentary.

Interpretation of structures and terminology can be summarized as follows. 1. Gilliam (1975b) chose not to use the term cheilocystidia for clavate cells found "present on the lamellar edges only," and not projecting beyond basidia. Such cells are scattered along the lamellar edge, sometimes indistinguishable from immature basidia except for cell breadth (10-16 µm broad for clavate cells versus 8-10 µm broad for basidia). Usually, however, frequent cheilocystidial cells form lobes or diverticula, immediately distinguishing them from basidioles. 2. Pleurocystidia are either absent or indistinguishable from basidioles before the latter have developed heterogeneous contents and clavate shape. For similar conclusions, see under My. copelandii . 3. Other east ern North American taxa on Quercus leaves = Gymnopus (sect. Perforantia ) foliiphilus, G. inflatotrama nom. prov., G. novomundi nom. prov. ( Androsacei ) and M. straminipes . 4. "Sterile stipes" (teste Gilliam 1975) are reminiscent of M. opacus , in which sterile stipes are common but interpreted as rhizomorphs ( Desjardin et al. 1993). 5. Caulocystidial wall thickness is not visible in PhC, but with IKI and BF, the inner surface of the wall becomes visible because the hyper-refringency of the caulocystidia disappears.

Desjardin (1989) provided type specimen descriptions of Marasmius copelandii Peck and M. olidus Gilliam. Desjardin (1987a) concluded that the differences between M. olidus and M. copelandii did not warrant species rank, and reduced Gilliam’s epithet as M. copelandii var. olidus . According to Index Fungorum, Gilliaim’s epithet (as Marasmius olidus or M. copelandii var. olidus ) has not been transferred to Mycetinis . Here, the differences from My. copelandii appear significant enough to accept My. olidus as a separate species within Mycetinis . The two taxa share the following: 1) strong odor and taste of garlic; 2) vestured stipe; 3) spore statistics; 4) doubtfully differentiated pleurocystidia; 5) basically clavate cheilocystidia; 6) inflated pileipellis elements. Differences between My. olidus and My. copelandii can be listed as follows: 1) basidiomata of My. olidus consistently smaller and less robust that those of My. copelandii ; 2) pileipellis free-form cells appear to be of different shape and extent; 3) lamellae distant ( My. olidus ) versus close to crowded; 4) cheilocystidia are doubtful in My. olidus , but when observed, they range from those figured by Gilliam to broadly fusiform and submammilate; 5) fruiting habitat on Quercus leaves; 5) distribution in eastern North America.

Alexander Smith’s preliminary identification of MICH-F-005239 (paratype of My. olidus ) as M. prasiosmus may have been predicated on habitat (i.e. on fallen Quercus leaves) and advice from his professor, Calvin Kauffman. Here, My. prasiosmus (= My. querceus ) is accepted in Mycetinis , but for an apparent European taxon, basidiomata of which are significantly larger than those of My. olidus , and the micromorphology of which is quite different from that of My. olidus , especially spore size and shape.

Redhead (1982) correctly reported that "pigmented hyphal walls" of stipe cortex of My. olidus (as Marasmius ) showed a color change to greenish gray in KOH solution. This reaction was also reported for M. prasiosmus , but this is true only for Kauffman’s concept of this name, for which M. olidus was later introduced. The American concept of M. prasiosmus is quite different from the European organism treated here as M. prasiosmus , in which the color reaction is missing.

Specimens examined.

United States, Florida, Alachua Co., vic. Gainesville, San Felasco State Park, Planera Hammock, Hwy 232, N29°47'00.2", W82°27'58.0", 12.XII.1987, coll DE Desjardin, TFB DED 4529 (TENN57177). Michigan, Liv ingston Co., vic. Pinckney, E.S. George Reserve, N42°27'30.88", W84°00'41.34", 4.X.1936. coll. A.H. Smith (AHS5034, as M. prasiosmus ), det. M. Gilliam (as M. olidus ) (MICH-F-00051235, paratype); Oakland Co., Proud Lake, N42°33'42", W83°31'43", 1.XI.1970, coll W.W. Patrick, Gilliam 997, (MICH-F-11400, holotype, p.p.); Proud Lake, N42°33'42", W83°31'43", 15.X.1955, coll. AH Smith (AHS51125) (as Marasmius prasiosmus ), det. M. Gilliam (as M. olidus ) (MICH-F- 0051239; paratype); Milford, 15.IX.1938, N42°35'32", W83°36'05", coll. A.H. Smith (AHS10936, as M. prasiosmus ), det. M Gilliam (as M. olidus ) (MICH-F-0051237, paratype); Haven Hill, N42°38'27.56", W83°33'48.28", 11.X.1956, coll. A.H. Smith (AHS62192, as M. prasiosmus ), det. M. Gilliam (as M. olidus ) (MICH-F- 00051238, paratype); Washtenaw Co., Ann Arbor, N42°16', W83°44', Cascade Glen, 17.IX.1907, coll. & det. C.H. Kauffman (as M. prasiosmus ), s.n. (MICH-F-00051241); vic. Chelsea, Mill Lake, N42°19'44", W84°05'22", 26.VIII.1972, coll. A.H. Smith (s.n., as M. prasiosmus ), det. M. Gilliam (as M. olidus , MG 1549 (MICH-F- 0051243, paratype); vic. Dexter, Silver Lake, N42°25'13", W83°57'35", 2.X.1936, coll. A.H. Smith (AHS5004, as M. prasiosmus ), det. M. Gilliam (as M. olidus ) (MICH-F- 00051244, paratype); vic. Dover, Silver Lake, N42°25'13", W83°57'35", 23.IX.1938, coll. A.H. Smith,(AHS11057, as M. prasiosmus ss. Kauffman), det. M. Gilliam (as M. olidus ) (MICH-F-0051245; paratype). North Carolina, Swain Co., GSMNP, Kephart Prong Trail, N35°35'23.7", W83°21'49.2", 25.VII.1991, coll V Antonín, VA 97/257 (BRNM; fragment TENN50012); Tennessee, Blount Co., GSMNP, Metcalf’s Bottoms, N38°40'54.1", W83°38'56.7", 24.V.2013, coll. Sam Morris, TFB 14211 (TENN68071).