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Page number:404 
Remarks (public):The genus is marked by two characters only: the presence of gloeocystidia and the amyloidity of the spores. These characters alone, however, do not form a sufficient base for a natural genus. If the criterion of sulfoaldehyde reaction of the gloeocystidia is added, one species, G. citrinum, falls out. If the presence of clamps, the density of the texture, the reaction of the hyphae to cottonblue, the nature of the spore wall, and the shape of the spores are considered, the genus may be sepa-
rated into seven species groups, all very small, as far as the Northeuropean species are concerned.
a) G. porosum-group with rather dense context, clamped, non-cyanophilous hyphae, and ellipsoid or reniform, verrucose spores (G. porosum and G. su baspe rispo ru m ).
b) G. convolvens-group with dense context, non-cyanophilous hyphae without clamps, besides gloeocystidia also encrusted, metuloid cystidia; ellipsoid, verrucose spores (one species).
c) G. ochraceum-group with very dense, pseudoparenchymatic context, no clamps, cyanophilous hyphae, and smooth or verrucose, ellipsoid spores (G. karstenii with verrucose spores, G. ochraceum with smooth spores).
d) G. furfuraceum-group with loose context of clamped, distinct, noncyanophilous hyphae, and globose, echinulate spores (one species).
e) G. luridum-group with dense, ceraceous context at least in the subhymenial trama, clamped, non-cyanophilous hyphae and smooth, ellipsoid to allantoid spores (G. leucoxanthum and G. luridum).
f) G. lactescens-group with fleshy context in the live state, narrow, noncyanophilous hyphae without clamps, numerous paraphysoid hyphae in the hymenium, smooth, ellipsoid spores (one species).
g) G. citrinum-group with gloeocystidia without oily contents and without sulfoaldehyde reaction, narrow hyphae without clamps in a loose context, and smooth, subglobose spores (one species).
The genus is certainly not very natural. G. citrinum, being the only species with gloeocystidia without granular contents and without aldehyde reaction, had better be separated, but as we cannot find a better place for it, we prefer to leave it in the genus. Moreover it resembles in some respects G. lactescens. Eriksson has earlier pointed at similarities between the G. luridum-group and the genus Aleurodiscus, and Boidin (Bull. Soc. d'Hist. nat. Toulouse 92 p. 284, 1957) has found relations between G. ochraceum and Stereum s.str.
Description type:Non-original description 
Description:Gloeocystidiellum Donk em. Donk, Fungus 26 p. 8, 1956. -Meded. Nederl. mycol. ver. 18-20 p. 156, 1931.
Fruitbodies resupinate, effused, thin to considerably thick (0,05-1 mm), generally ceraceous when wet and alive, at least in the young fruitbodies, firmer with age and when dried, membranaceous to coriaceous; hymenium more or less thickened; hyphal system monomitic, with or without clamps; basal layer of more or less horizontal hyphae present in some species but is generally inconspicuous; density of the hyphal context varying, in some species the tissue is composed of distinct, loosely interwoven hyphae, in others it is very dense, pseudoparenchymatic; gloeocystidia (pseudocystidia) always present, thinwalled, tubular, sinuous, normally (in water or KOH) with granular, oily, yellowish contents (in cottonblue the oil coalesces to larger oildrops), which in most cases react positively to sulfovanilline; encrusted cystidia in one species, lacking in the others; basidia clavate, normally with 4 sterigmata, in a dense palisade; spores varying in size and shape, always amyloid, smooth or warted to echinulate.
Genotypus: Gloeocystidiellum porosum (Berk. & Curt.) Donk.
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