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Page number:468 
Remarks (internal):The chamaeleon colours exhibited by E. effusa have undoubtedly led to confusion. Indeed, the specimens examinee above were provisionally assigned to three different species, until the opportunity to see abundant material (at Fernworthy Forest) showed all the variations side by side. Some if not al: of these variations are due to the thickness and maturity of individual fruit bodies plus the humidity at the time of collection. In wet weather, fruit bodies are hyaline, gelatinous, and variously tinted. In damp weather, a dense pruina forms which turns all fruit bodies white and opaque, at least until touched.
Wells (1961) placed Exidiopsis effuse in synonymy with E grisea (Pers.) Bourd. & Maire, but later (Wells, 1987) showec through cultural intercompatibility tests that the two species were distinct. Unfortunately, no descriptions of the specimens used in the tests were provided. However, Oberwinkler (1963), whose species parameters were used by Wells when selecting his test specimens, distinguished E. grisea by its typical occurrence on Abies alba, its colour (' grau bis stahlblau'), and comparatively short spores (9-14 x 3.5-5 µm). Exidiopsis effuse, by contrast, is said to occur on deciduous wood, has a fruit body described as 'blaulich mit rosa Stich', and has longer spores measuring (10-)13-17 x 3.5-4.5 µm. The Devon and are described here. The fourth species, Exidiopsis calcea (Pers.) Wells, has been frequently confused with E. effusa and its occurrence in Britain requires confirmation. The majority of extra-limital species currently assigned to Exidiopsis have conspicuous fruit bodies, possess hyphidia, and should almost certainly be retained within the genus. New combinations are provided for the minority, mostly European, which are clearly to be excluded.
Devon collections of both species confirm Oberwinkler's macroscopic distinctions, but show no differences in spore shape or size.
Ingold (1992), who received part of the Perivale specimer and germinated spores, notes the production of comma shaped microconidia in culture. Though impractical for routine identification, this feature is certainly of taxonomic significance at the level of genera or above. At least one species currently assigned to Exidiopsis produces microconidia of an entirely different kind, thereby underwriting the more obvious morphological reasons for splitting the genus.
Description type:Non-original description 
Description:Exidiopsis effusa (Bref. ex Sacc.) Moll., Bot. Mitth. Trop. 8: 82 (1895).
Sebacina effusa (Bref. ex Sacc.) Maire, Bull. Soc. mycol. France 18: 67 (1902). - Thelephora effusa Bref. ex Sacc., Syll. Fung. 6: 541 (1888).
Basidiomes extensively effused, thinly ceraceous to sub-gelatinous, entirely covered with an easily removed white pruina when damp (absent in wet weather); when this pruina is present, fruit bodies appear entirely white, sometimes with pink, violaceous, or greyish tints; without a pruina, fruitbodies appear gelatinous, hyaline, reddish pink, or violaceous blue-grey. On drying, fruit bodies form a very thin, white, red, or greyish-white crust. Hyphae clamped at all septa, rather thin, ca 1.5-2.5 µm wide, forming a branching, basidia-bearing hymenium in a gelatinous matrix. New hyphal branches normally arise from the bases of basidia. Hyphidia nodulose and weakly branched, ca 0.5-1.5 µm wide, forming a layer with or above the basidia at the hymenial surface, becoming gelatinized and difficult to differentiate in older specimens. Basidia normally 4-septate, ovoid to ellipsoid or pyriform, rather large, around 16.0 x 10.0 µm, clamped at the base, the clamp often forming an open loop in young basidia. Sterigmata tubular, sinuous, extending almost indefinitely to reach the hymenial surface. Spores depressed or weakly allantoid, ca 10.5-14.0(-15.0) x 3 5-4 5 µm (See Table 1), frequently replicating, germinating by one or more germ tubes.
Specimens examined: on fallen Corylus branch, Bovey Great Plantation, Devon (SX 8275), 23 Mar. 1991, P. Roberts 187, K; recollected or same branch, 14 Mar. 1992, P. Roberts 374, K; on decorticated log of Pinus radiata, Lincombe Slopes, Torquay, Devon (SX 9363), 2E June 1991, P. Roberts 258, K; on dead attached Fagus branch, Fernworthy Forest, Dartmoor, Devon (SX 6583), 8 Mar. 1992, P Roberts 370; same location, on fallen Fagus branch, 15 Mar. 1992, P Roberts 378, K; on Ulmus log, Perivale Wood, Middlesex (TQ 1583), 12 May 1991, A. Henrici.

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