Parasola megasperma (P. D. Orton) Redhead, Vilgalys & Hopple

Zhu, LiYang & Bau, Tolgor, 2025, Emendation of morphology and infrageneric standards of Parasola (Psathyrellaceae, Agaricales) and its species diversity in China, IMA Fungus 16, pp. e 143796-e 143796 : e143796-

Parasola megasperma (P. D. Orton) Redhead, Vilgalys & Hopple , in Redhead, Vilgalys, Moncalvo, Johnson & Hopple, Taxon 50 (1): 236 (2001).

Figs 12 o , 16

Basionym.

Coprinus megaspermus P. D. Orton , Notes R. bot. Gdn Edinb. 32 (1): 141 (1972).

Description.

Pileus 8–11 × 6–9 mm when still closed, 15–18 mm when mature, at first semiglobose to mitriform, expanded pileus conical to flattened, mostly with a depressing disc at center; dry; ochreous to dark yellow-brown at center, surrounded with a water-soaked circulus, pale brown-gray at margin, dark yellow-brown at ridge of plication; sulcate-striate up to center. Context extremely thin, almost unseen in membrane part of pileus, cream to sordid yellow, odor and taste not distinctive. Lamellae crowded, free and remote from stipe, with a circular empty space which is visible around the apex of the stipe, 1 mm in wide, L = 35–42, I = 0 or 1, first pale-yellow gray then become gray to purple-gray, or dark gray; hardly deliquescent with age. Stipe 48–71 × 2–3 mm, cylindrical, hollow, equal or slightly attenuate towards the apex, cream and darker at base, glabrous. Spore print not recorded.

Basidiospores [37, 2, 1] (13.1 –) 14.4–15.1 (– 16.3) × (9.3 –) 10.1–10.5 (– 11.9) × (8.3 –) 8.8–9.5 (– 9.7) μm, Q 1 = 1.28–1.55, Q 2 = 1.59–1.61, av. Q 1 = 1.43, av. Q 2 = 1.60; ellipsoid, with apical papilla and convex base in front view, narrow ellipsoid in side view; smooth, dark brown to almost black; inamyloid; germ pore central, 2.0–2.9 μm wide. Basidia dimorphic, 17–44 × 11–15 μm (in average 32 × 13 μm), sterigma 4–6 μm, clavate, sometimes constricted in middle part, hyaline, 4 - spored, surrounded with 5–7 pseudoparaphyses; subhymenium yellow brown, composed of subglobose, ellipsoid, oblong or cylindrical elements. Cheilocystidia 25–55 × 23–34 μm, abundant, subglobose, utriform, ellipsoid or sublageniform, smooth, colorless, thin-walled. Pleurocystidia very rare, when present 49–75 × 22–26 μm, oblong to cylindrical, smooth, colorless, thin-walled. Lamella trama regular, 6–10 μm wide, hyaline, colorless, thin-walled. Pileipellis a hymeniderm, made up of sphaeropedunculate and clavate cells, 30–43 × 13–21 μm, hyaline, with yellow-brown hue at base; pileus trama hyphae densely interwoven, thin-walled or slightly thick-walled, hyaline, yellow-brown, 5–8 μm wide; sclerocystidia absent. Stipipellis hyphae parallel, 4–8 μm wide, hyaline, thin-walled, occasionally with short branches; hyphae of stipe trama 9–20 μm wide, colorless, thin-walled; caulocystidia unseen. Clamp connection present.

Ecology.

Solitary, subfasciculate or in small groups, grow on sandy soil or soil with manure in grassy place. Fruiting in July to August. Recorded with certainty from Netherlands, Britain, Poland in Europe (Uljé 2005; Gierczyk et al. 2011; Schafer 2014) and America (Mainland and Hawaii Islands) (Keirle et al. 2004); other reports also from New Zealand (https://www.gbif.org/); only known from Inner Mongolia Autonomous Region in China so far.

Specimens examined.

CHINA • Inner Mongolia Autonomous Region, Tongliao City, Horqin Left Back Banner, Udantala Forest Farm , July 16 th 2022, 42°59'31"N, 122°46'37"E, 207 m a. s. l., T. Bau, W. N. Hou, HMJAU 60099 (H 2207124) ; CHINA • Inner Mongolia Autonomous Region, Hulunbuir City, New Barag Left Banner, Amugulang Town, Jianggaihuduge , 48°08'41"N, 118°21'05"E, 696 m a. s. l., August 7 th 2022, T. Bau and L. Y. Zhu, HMJAU 64101 (Z 22080716) .

Notes.

Parasola megasperma could be easily distinguished from other species without sclerocystidia by its large dark ellipsoid basidiospores which are up to 14 μm in average. Moreover, the dark yellow-brown ridge on pileus when mature and the water-soaked circulus around the brown central could also be recognizable characteristics of this species. Parasola megasperma has been often confused with Parasola schroeteri and Parasola hercules due to the relatively large basidiospores shared by these three species. However, the shape of basidiospores differ significantly: Parasola hercules exhibits basidiospores that are predominantly rounded triangular to weakly 5 - or even 7 - angular, while those of Parasola schroeteri are consistently rounded triangular (Uljé 2005).

The presence of pleurocystidia in Parasola megasperma varies with specimens. In the specimens examined here, pleurocystidia were very rare and exclusively cylindrical. In contrast, other studies by Keirle et al. (2004), Uljé (2005) and Gierczyk et al. (2011) reported pleurocystidia as ellipsoid to narrow ellipsoid. Notably, this structure was not mentioned in Schafer’s description (2014).

Figures

Figure 12. Basidiomata of species in Clade Plicatilis and Clade Misera of sect. Parasola. a – c Parasola tenuissima: a HMJAU 64085, b HMJAU 64086, c HMJAU 64084; d – f Parasola chowii: d HMJAU 60358, e HMJAU 60374, f HMJAU 64099; g – l Parasola neoplicatilis: g, h HMJAU 64087, i HMJAU 64088, j, k HMJAU 60084, l HMJAU 64089; m, n Parasola plicatilis: m HMJAU 60367, n HMJAU 60366; o Parasola megasperma HMJAU 60099.

Figure 16. Basidiomata and microscopic structures of Parasola megasperma: a basidiomata (HMJAU 64101), b pileipellis (HMJAU 60099), c basidiospores (HMJAU 60099), d basidia (HMJAU 60099), e cheilocystidia (HMJAU 60099), f pleurocystidia (HMJAU 60099, HMJAU 64101), g stipitipellis (HMJAU 60099). Scale bars: 1 cm (a); 10 μm (b – g).