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 Add this item to the list   Megalocystidium Jülich
Page number:77 
Remarks (internal):The original description did not specify the characters which distinguish this genus from allied genera. Presumably it was the combination of all the characters listed in the description which were important. Three species were included: C. leucoxanthum, C. lactescens Berk. and C. luridum Bres. Boidin and Lanquetin (1983) placed Megalocystidium in synonymy under Vesiculomyces. Hjortstam (1987b) did not separate Megalocystidium from Gloeocystidiellum.
Current status Megalocystidium leucoxanthum and M. luridum are considered, by us, to be distinct species. However, some Scandanavian collections with spores intermediate between the two suggested to Eriksson and Ryvarden (1975) that the extremes of the species should be tested by intercollection matings. Corticium lactescens is the type species of Gloiothele. The principal characters of Megalocystidium are 1) ellipsoid to suballantoid, relatively long spores with a small apiculus, 2) clamp connections, 3) sulfo-negative, tubular, often strangulated gloeocystidia, 4) long, slenderly clavate basidia, and 5) membranous to ceraceous basidiomes. Both M. leucoxanthum and M. luridum have been reported from North America, but M. luridum is considered to be extralimital (see details under Excluded Names). In addition a new species, M. montanum is proposed herein.
Description type:Non-original description 
Description:Megalocystidium Jülich
Persoonia 1: 140, 1978.
Type species Corticium leucoxanthum Bres.
Basidiomes effuse, typically several cm long and broad, thin to 0.6 mm thick, membranous, ceraceous, in age some deeply fissured, pale yellow, yellow, buff, pallid to tan, lignicolous or corticolous. Hymenial surface smooth, but conforming to the topography of the substrate. Subiculum pallid to white, thin, dense. Hyphal system monomitic. Generative hyphae typically arranged in a narrow layer parallel to and adjacent to the substrate, then becoming perpendicular to the substrate and slightly woven between the gloeocystidia and developing hymenium, with clamp connections, 2-5 µm diam, the walls hyaline, thin or moderately thickened in some species, nonamyloid, acyanophilous. Gloeocystidia cylindrical or subfusoid, sinuous, some strangulated, typically 50-160 x 7-16 µm; the walls hyaline, thin; the contents oily to granular and pale yellow in KOH, sulfo-negative. Basidia slenderly clavate, about 35-65 x 5-8 µm with four sterigmata. Basidiospores ellipsoid to suballantoid, relatively large, typically 9-18 x 4-7 µm, the walls smooth or minutely verrucose, hyaline, thin, amyloid, acyanophilous, with a minute apiculus.

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