Mycetinis scorodonius (Fr.: Fr.) A.W. Wilson & Desjardin., 2005. Mycologia 97: 678.

Petersen, Ronald H. & Hughes, Karen W., 2017, An investigation on Mycetinis (Euagarics, Basidiomycota), MycoKeys 24, pp. 1-138 : 54-57

11. Mycetinis scorodonius (Fr.: Fr.) A.W. Wilson & Desjardin., 2005. Mycologia 97: 678.

Agaricus scorodonius ≡ Fr. 1815. Observ. Mycol. 1: 29.] ≡ Agaricus scorodonius Fr. 1821. Syst. Mycol. 1: 130. ≡ Marasmius scorodonius (Fr.) Fr. 1838. Epicrisis 379. ≡ Gymnopus scorodonius (Fr.) J.L. Mata & R.H. Petersen. 2004. Mycoscience 45: 221.

Type specimen

(neotype, design. Antonín and Noordeloos 1993). Fungi Exsic. Scandinavia, no. 1 (Sweden, Stockholm, Autumn, 1889, coll. A. Romell (BR; isoneotypes B, BP, W).

Diagnosis.

1) Basidiomata of moderate size (pileus 10-30 mm broad; stipe 40-60 × 0.5-1.3 mm); 2) stipe brown or orange brown upward, midsection off-white, downward mahogany to red-brown, glabrous; 3) pileipellis at pileus margin with inflated hyphal termini and broom cell-like cells; 4) spores ellipsoid to amygdaliform, Lm = 9.0 µm; 5) strong garlic odor and taste; 6) distribution in Europe and North America (rare on North American west coast).

Description.

Basidiomata (Fig. 70) of moderate size. Pileus (3-)10-30 mm broad, almost hemispherical when young, convex with slightly raised disc, then convex to almost applanate, even to slightly depressed on disc, smooth, glabrous to subglabrous, hygrophanous; disc neutral brown, "sayal brown" 6C5, “cinnamon” 6B5, brownish orange 6C4, when moist brown, yellow-brown or ochre, sometimes paler towards margin; margin slightly involute then more or less straight, undulating, distinctly pallescent on drying to pale brown 6D5, pale ochraceous, "pale ochraceous buff" 4A2, "pale pinkish cinnamon" 6A2, pinkish, "pinkish buff" 6A3, or dirty white, smooth or slightly radially rugulose, even subsulcate when old. Lamellae adnexed to adnate to a thin pseudocollarium which becomes most visible with lamellar secession in drying, subdistant, close to crowded, total lamellae 38-48, through lamellae 15-20 (in robust form total lamellae 72-97, through lamellae 27-32), slightly intervenose when old, narrow (lamellae -1.5 mm broad); white to orange white 5A2, near "pale ochraceous buff" 4A2, "pale pinkish cinnamon" 6A2 to off-white when fresh; frequent necropigment upon drying and storage to dusky cantaloupe color with a hint of pink to make "light ochraceous buff" 5A4 to "pinkish buff" 6A3; lamellulae in at least two ranks, often rudimentary; lamellar edge concolorous with lamellar face, minutely pruinose. Stipe (15-)40-60 × 0.5-1.5(-3) mm, terete to slightly compressed, often slightly broadened apically, sometimes tapering gradually downward, hollow, often appearing insititious, but usually with poorly developed basal disc or basal mycelium, glabrous to sometimes delicately pruinose at apex only, pallid to pale brown at apex, "tilleul buff" 7B2, drying to "cinnamon buff" 6B4, brownish orange 6C4, downward off-white becoming brown, "sayal brown" 6C5, dark reddish brown 7F8, mahogany, "Verona brown" 6E5, or orange-brown, "Brussels brown"6E6, "Mikado brown" 7C6, "mummy brown" 6F8 towards base, with fine rusty tomentum at base. Context thin, white to pale brown. Rhizomorphs not reported. Odor weak to strong of garlic, rarely lacking; taste usually alliaceous.

Habitat and phenology.

Clustered to gregarious, not fastidious of substratum for fruiting, coniferous needles, various dead deciduous leaves from forest trees ( Fagus , Quercus , Alnus , Acer , etc.) and heaths; widely distributed through Europe including western Russia, Scandinavia, northern Africa and eastern North America (see Antonín and Noordeloos 2010), reported as rare in California; Autumn.

Pileipellis at pileus margin a mixture of three major structures: 1) roughly hymeniform layer of inflated cells (Figs 71 A–D, 72 A–F) (16-)33-40(-45) × 14-23 µm overall, thick-walled (wall -1.5 µm thick, hyaline, smooth or minutely roughened, stalked (stalk 7-20 × 3.5-5.5 µm), clamped; 2) similar inflated termini, overall 33-47 × 14-33 µm overall, stalked (stalk 12-18 × 3.5-6 µm, clamped), usually expanded distally and then beset by complex lobate to diverticulate processes (Fig. 72 G–J); diverticula papillate, fin-like, lobate to digitate, -9 µm long, subrefringent (PhC); and 3) differentiated broom cell-like pileocystidia (Fig. 72 E–L) 21-28 × 8-16 µm overall, stalked (stalk 3-8 × 3.5-5.5 µm), somewhat swollen distally, thick-walled throughout, surmounted by a cluster of outgrowths; outgrowths digitate to catenulate, hyper-refringent (PhC), often knobbed at apex, occasionally dichotomous. Pileipellis over pileus disc constructed of two hyphal types: 1) a coarse hymeniform layer composed of clavate, pyriform, utriform, vesiculose, sometimes slightly fusiform or lobate elements, (5.0-)20-42(-58) × 13-24(-35) µm, smooth or less frequently with a few digitate apical projections (not true broom cells) up to 6 µm long, or only somewhat apically roughened, thin- to thick-walled (wall up to 1.5-2.0 µm, hyaline to yellow-brown); and 2) free-form hyphal termini, coarsely complexly lobed, stalked (stalk 5-12 × 4-6 µm), overall 15-30 × 17-40 µm; individual lobes and hyphae 5-8.5 µm diam, thin- to firm-walled; contents heterogeneous. Pileus and lamellar tramae loosely interwoven; hyphae of two types: 1) 3-7.5 µm diam, firm-walled, conspicuously clamped; and 2) 3.5-9 µm diam, thin- to firm-walled, conspicuously clamped; contents heterogeneous. Pleurocystidia (Fig. 73) 31-40 × 5-7 µm, cylindrical to narrowly fusiform, acutely rounded at apex, conspicuously clamped; contents more or less homogeneous. Subhymenial hyphae branched, cylindrical, hyaline, 2.0-5.0 µm wide, clamped. Basidioles clavate, cylindrical to subampulliform, obscurely clamped; basidia (Fig. 74) 28-42 × 7.0-9.0 µm, clavate to subcapitulate, (2-)4-sterigmate, obscurely clamped; contents heterogeneous, multiguttulate. Basidiospores (Fig. 75) (6.5-)8.0-10.0(-11.0) × (3.5-)4-4.5(-5.5) µm (Q = 1.55-2.57; Qm = 1.93; Lm = 9.0 µm), ellipsoid, ovate to amygdaliform, smooth, thin-walled, inamyloid; contents heterogeneous, minutely multiguttulate. Cheilocystidia (Fig. 76) locally plentiful, siccus -type, (12-)23-40 × 14-21 µm overall, staked (stalk 12-24 × 3-5.5 µm, obscurely clamped), often inflated distally, surmounted with a complex of diverticula; diverticula 2-10 × 1-1.5 µm, gnarled, often dichotomous. Stipitipellis a cutis of 3.0-12.0 µm wide, cylindrical hyphae with yellow-brown to dark brown, slightly thickened (-2.0 µm) walls. Caulocystidia not differentiated, but sometimes scattered, cylindrical, terminal endings of cortex hyphae present.

Commentary.

Description of pleurocystidia may be somewhat miscast. Traditionally, pleurocystidia and basidioles have been confused. The description above is based on the following circumstances: 1) more acutely rounded pleurocystidial apex than subcapitulate basidioles; 2) homogeneous pleurocystidial contents as compared with the heterogeneous contents of basidia and maturing basidioles; and 3) usual length of both structures not acceding that of basidia.

The marasmioid cheilocystidia were sought in three European collections (Belgium, Netherlands, Sweden) in at least two different mounts from two different basidi omata of each collection, so the sudden abundance of highly differentiated cheilocystidia in TFB 7261 was surprising. Moreover, the entire lamellar edge was covered and so was sterile. In other lamellar margins, only structures resembling the clavate shapes found in other species of Mycetinis were observed.

Mycetinis scorodonius may exist in two forms: 1) pileus -20 mm broad; 2) lamellae distant, narrow; 3) stipe slender (1-2.5 mm broad, terete), tapering downward; versus 1) pileus 15-32 mm broad; 2) lamellae crowded, well-developed; 3) stipe robust (2-4 mm broad, often compressed). These forms share the following: 1) strong odor and taste of garlic when fresh; 2) smooth pileus with brown disc and tan limb; 3) pileocystidia in pileipellis from pileus margin. To this writing (X.2016), the robust form has been seen from Belgium, Samara Region, Russia and North America; the slender form has been limited to the Leningrad Region, Russia.

There were sufficient ITS sequences to analyze population structure in Mycetinis scorodonius (Fig. 77). European and North American populations are not mutually exclusive. There is a distinct North American haplotype but European collections seem to be a mix of two haplotypes; one, a North American-like haplotype and one not found in North America termed “European-like” in Fig. 77. A single North American collection has the European-like haplotype and a collection from Mexico is heterozygous for both European-like and North American-like haplotypes.

The origin of the two European haplotypes is uncertain but it would appear that some gene flow between Europe and North America has occurred, either by long distance spore dispersal or human mediation.

Gordon (1994) and Gordon and Petersen (1998) employed three methods in a taxonomic analysis of numerous pan-Atlantic collections of My (as Marasmius ) scorodonius . Using basidiome collections and derived cultures of European and eastern North American specimens, collections were submitted to Numerical Taxonomy and Multivariate Analysis System (NTSYS-pc; ( Rohlf 1992)) and UPGMA cluster analysis, pairing experiments using single-basidiospore isolates and laccase electrophoresis. Although some micromorphological variation was found (i.e. presence/absence of cheilocystidia), European and North American collections were intermixed, with no clear-cut separation detected. Likewise, pairing experiments indicated that European and eastern North American collections were sexually intercompatible, indicating a single biological taxon across the trans-Atlantic barrier. Laccase electrophoresis, however, clearly separated European versus eastern North American collections, indicating lack of long-distance genetic exchange across the oceanic barrier. Altogether, results were not incompatible with conclusions shown here by use of DNA sequences.

Although apparently rare, one specimen of My. scorodonius from Washington (state) has been examined. Another from California is reported in Mycoportal (Humboldt Co., Patrick’s Point State Park, 25.IX.1968, coll. & det. HD Thiers, annot. DE Desjardin, SFSU-025263).

Basidiomata of My. alliaceus and My. copelandii do not exhibit differentiated pileocystidia. In My. copelandii , free-form cells accompany inflated hyphal termini, but in My. alliaceus , the inflated elements are the only element observed, although at pileus margin some individuals are found to produce apical outgrowths.

Specimens examined.

Belgium, Dimpre, vic. Heer, Massembre, N50°09.360", E4°51.224", coll. KWH, TFB 13746 (TENN65123). Canada, Nova Scotia, Kejimkujik National Park, N44°22'44", W65°20'32", Rogers Brook Trail, 4.VIII.1992, coll SA Gordon, TFB 5031 (TENN51442); Kejimkujik Nat. Park, Grafton Lake Loop Trail, N44°22'55", W65°10'55", coll. SA Gordon, TFB 5038 (TENN-F- 53468). The Netherlands, Gelderland Prov., Wageningen, N51°58'12", E5°39'54", 3.VIII.1959, leg. K. Bakker, det. C. Bas, LRH 23881 (TENN-F-23881). Russia, Leningrad Region, Dist. Lindylovskaye, Rocha Reserve, N60°14.30', E29°32.394', 25.VIII.1999, coll RHP, TFB 10400 (TENN58260); Samara Region, Zhijulevsky Reserve, vic. St. Nicholas Spring, Shirayevo Valley, N53°23.425', E49°57.939', 17.VIII.2004, coll RHP, TFB 12168 (TENN-F-60107). Sweden, Uppland, vic. Uppsala, Tärnby Lund, N59°51' 345", E17°38'05", 4.IX.1994, coll RHP, TFB 7261 (TENN-F-53568); Västergötland, Lillaedet, Myrtuvan, N58°08'30", E012°02'40", 19.IX.1991, coll/ SA Gordon et al., TFB 3796 (TENN-F-50533). United States, Georgia, Rabun Co., Rte 28, approx. 1 mi into GA, N34°57'11.32", W83°11'00.70", 1.VI.1993, coll RHP (as M. copelandii var. olidus ), TFB 6213 (TENN52873); Maine, Hancock Co., Lamoine, N44°29'22", W68°18'35", 25.VII.1992, coll. SA Gordon & W. Litten, TFB 5005 (TENN-F-53474); Massachusetts, Berkshire Co., vic. North Adams, N42°42'03", W73°06'33", 16.IV.1986, coll. DE Desjardin, DED 4060 (TENN-F- 54179); Michigan, Marquette Co., Powell, vic. Ives Lake, N46°50'47", W87°50'05", 28.VIII.1971, coll. RHP, TENN-F-036156; North Carolina, Macon Co., vic. Highlands, Nantahala Nat. For., Blue Valley, Pickelsimer’s Falls Trail, N35°00'50", W83°14'39", 18.VII.1991, coll. SA Gordon., TFB 3701 (TENN-F- 50689); Tennessee, Blount Co., GSMNP, Cades Cove, Parsons Branch Rd., N35°33'44", W83°22'48", 14.IX.1987, coll DE Desjardin, DED4500 (TENBN-F-54182); GSMNP, Cades Cove, vic. Oliver cabin, N35°36'25.42", W83°47'39.03", 12.VI.2013, coll. RHP, TFB 14229 (TENN68086); Sevier Co., GSMNP, Greenbrier area, N35°42'28", W83°22'48", 19.VII.1986, coll. DE Desjardin, DED 3875 (TENN-F- 54209); GSMNP, Mt. LeConte, N35°39'18", W83°26'28", 4.VI.1957, coll. LR Hesler, TENN-F-009183. Washington, King Co., Seattle, Univ. Washington campus, N47°39'14.83", W122°18'28.53", 12.X.1942, coll. & det. DE Stuntz, STz 1239 (WTU-F-9221).