Gloeophyllales » Gloeophyllales genera¬†incertae sedis » Pileodon

Pileodon megasporus

Pileodon megasporus P. Roberts & Hjortstam 1998, in Hjortstam et al., Kew Bulletin, 805-827 (1998).

Diagnosis: Basidiomes tough, effuso-reflexed, up to 70 x 30 mm with narrow pileus up to 12 mm deep; pileus dark brown, woody-hard, smooth, concentrically ridged; hymenial surface dark tawny brown, finely odontioid under lens, with distinct margin narrowly edged whitish-buff, often with remains of previous hymenial surfaces below. The odontioid spines appear to be sterile, and thus represent hyphal pegs arising from the hymenial surface. Hyphal system dimitic; generative hyphae 1.5 - 2.5 pm diam., hyaline, thin-walled, with clamp-connections, often also with unclamped secondary septa; skeletal hyphae 2 - 7 pm diam., brown, with walls up to 3 pm thick; often with distinct, sometimes terminal, swellings up to 12 pm diam.; some hyphae distinctly nodulose; pileal hyphae densely compacted, with short, finely nodulose, hyphal elements at the pileal surface (though these could possibly belong to a hyphomycetous fungus). Basidia c. 60 x 12 pm, with additional narrow stalk up to 30 pm long; sterigmata 4, up to 6 pm long. Basidiospores cylindrical (Q = 3.4 - 3.8), 22 - 30 x 6.5 - 8 pm, hyaline becoming brown, with thin or slightly thickened walls, inamyloid, non-dextrinoid, acyanophilous. Figs. 4 & 5.

The dimitic structure, semi-pileate basidiome, odontioid hymenium of sterile hyphal pegs, clamped generative hyphae, and unusually large, browning basidiospores, together represent a unique combination of characters for Pileodon megaspora, which has no close affinity to any existing genus or species. Superficially, the collection resembles a member of the Hymenochaetales (e.g. Hymenochaete rubiginosa or Phellinus spp.) in colour, habit, and general appearance. But microscopically it is entirely different, having clamped hyphae (unknown in the Hymenochaetales) and large, stalked basidia. In the Boletales, the genus Corneromyces Ginns, described from Borneo, has spores of similar dimensions, but strongly amyloid and with highly thickened walls. Moreover, the basidiome is soft, effused, and monomitic. The closest relative may be Epithele (Pat.) Pat. (Stereales), species of which typically have large basidiospores and sterile teeth (or hyphal pegs). On this basis, Pileodon is here tentatively assigned to the Stereales.

Index Fungorum Number: IF521254

Figure 1. Pileodon megaspora. Effused-reflexed basidiome (shown life-size) with undulate, concentrically-ribbed pileus. Part of holotype collection, K(M) 43725.

Figure 2. Pileodon megaspora. Nodulose pileal elements arising from compacted surface; thick-walled, secondarily- septate, brown context hypha and nodulose hypha; thin-walled, hyaline, clamped hyphae; immature and mature basidia, showing distinct stalks; thin- to thick-walled basidiospores. Holotype, K(M) 43725.

Reference:

Hjortstam, K., Roberts, P. J., & Spooner, B. M. (1998). Corticioid fungi from Brunei Darussalam. Kew Bulletin, 805-827.

 

About Basidiomycota

The webpage Basidiomycota provides an up-to-date classification and account of all genera of the phylum Basidiomycota.

 

Supported by 

Thailand Science Research and Innovation (TSRI)

project entitled:

"Macrofungi diversity research from the Lancang-Mekong Watershed and surrounding areas"

(Grant No. DBG6280009)

Contact

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