Pluteus muscicola Stevenson (26 D) Fig. 17 = Pluteolus muscicola (Stevenson) comb. nov. (Basionym: P. muscicola Stevenson, Kew Bull. 16: 72, 1962)

Spores elliptic, rust: brown to ochraceous, smooth, with broad apical germ pore, 8-11 X 4.5-5.5 µ. Cuticle of articulate cells forming an hymeniderm, with brown plasmatic pigment, clamp connections none.

Basidiospores orange-tawny in mass, 7.5-8.5(-9.5) x 4.5-5.5(-6) µm ellipsoid, very slightly amygdaliform in side-view, smooth, relatively thick-walled, truncate from broad germ-pore. Basidia 4-spored, clavate-pedicellate, hyaline, in 'pavement' with shorter

brachycystidia. Cheilocystidia lageniform with short to elongate neck, 17.5-35 x 6-10.5(-12) µm, apex slightly swollen 2.5-5(-7) µm; pleurocystidia absent. Pileipellis a mixture of chains of inflated cells, 14-22.5 µm  long, and vesiculose to spheropedunculate cells, 29-40 x 15-26 µm, some end-cells filled with pale greyish to lilaceous brown vacuolar sap, long, flexuous, septate hyphae also present pushing through gelatinous pellicle.

The spotting, pattern of raised lines and scrobiculae of the pileus and their colouring is very variable, and probably depends on age of the basidioma and environmental conditions, although the microscopic characters are relatively constant. However, a collection on Nothofagus fusca (Horak ZT 67/192) differed in the cheilocystidia being slightly forked at their apex, the basidiospores slightly paler in overall pigmentation and slightly smaller, and the pileipellis apparently lacking numerous elongate hyphae. The collection, however, comes well within the variation accepted for B. muscicola.

Horak (1971b) agrees with our disposition of Stevenson's taxon although he prefers to use the generic name Pluteolus. Stevenson's material differs only in that a few 2-spored basidia were found; this undoubtedly explains the slightly larger spore-size for the type material; also see Stevenson, 1982a. ZT 69/46 is somewhat different in that although the immature pilei are scrobiculate the old pilei have dark raised lines upon them.