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Page number:153 
Remarks (internal):Selection of the type specimen for Parmasto's forma incarnatus is confused by the fact that Burt on two occasions (1917, 1919) selected a lectotype for M. incarnatus Schw. The two specimens in FH and PH represent different species. The specimen selected in 1917 and in PH is M. incarnatus of Schweinitz, Fries, and others. The specimen selected in 1919 and in the Curtis Collection (FH) is, according to Burt's description and discussion, M. tremellosus with an unusually reddish hymenium (I have seen European collections with a very distinctly red color, in particular there are two from Ricken at S). Thus the type specimen for forma incarnatus is in the Curtis Collection and has no connection with the type of M. incarnatus Schw., which is in PH (see similar comment by Ginns 1970, p. 245). I have examined all seven specimens that are labelled M. incarnatus in the Curtis Collection (FH). The collections from Alabama (Peters 428), Pennsylvania (Michener 478), South Carolina (Society Hill, Oct. 1849), and Texas (Billings 114) are cited by Burt (1919) and I have deter-mined them to be M. incarnatus. Other specimens that Burt cites (1919) are M. tremellosus, including the one labelled "Merulius incarnatus Schw! Herb. Schwein." which presumably is the one that Burt thought should be type.
The conical, waxy hyphal strands which ex-tend into the fibrous context are particularly evident in basidiocarps where insects preferentially have removed the fibrous layer. Merulius incarnatus is the species with basidiocarp features and habit most similar to M. tremellosus. The former has spores 2-3 µm wide, resinous or other deposits in the abhymenial hyphal layer of the context, a few refractive hyphae in the context, heavy deposits of yellowish granules at the base of the folds, and a comparatively broad granule-impregnated zone adjoining the subhymenium, all features which distinguish M. incarnatus. Variations of Meruliopsis corium, Phlebia rufa, and rarely Gloeoporus dichrous are similar externally. Meruliopsis corium is distinguished by its simple-septate hyphae, P. rufa has spores 2-3 t wide and gloeocystidia. Gloeoporus dichrous has narrower spores and the hymenial surface is usually distinctly poroid and pale purple with pores, five to seven pores per millimetre. Merulius tremellosus, M. incarnatus, and G. dichrous, al-though distinct species, have similar microscopic features of the basidiocarps. The cultural characters of each are very distinct (cf. the species code of each).
In related studies Singh et al. (1961) have reported the presence of a Ptychogaster stage for M. tremellosus, and Moore and McAlear (1961, 1962) have illustrated its hyphal ultrastructure.
 
Description type:Non-original description 
Description:Merulius tremellosus Fr., Syst. Mycol. 1: 327. 1821.
= Xylomyzon tremellosum, Pers., Mycol. Eur. 2: 30. 1825.
=Merulius tremellosus f. incarnatus Parm., Izv. Akad. Nau'k Estonsk. S.S.R., Ser. Biol. 16: 386. 1967 ut "(Schw.) Parm.... non Fr. nec auct.; vide Burt . . . (1919)" i.e. M. incarnatus non Schw. q.e. in Burt (1917) sed in Burt (1919).
= M. imbricatus Balfour-Browne, Br. Mus. (Nat. Hist.) Bot. Bull. 1: 192. 1955.
Basidiocarps effused or effused-reflexed, often imbricate, separable when fresh, often confluent, extent variable, usually 5 x 3 but up to 25 x 10 cm and 5 mm thick; margin where effused pale yellow to orange-red, occasionally darker, waxy, translucent, fimbriate, up to 2 mm wide; where reflexed soft and cartilaginous when fresh, drying horny, up to 4 cm wide and 4 mm thick, the abhymenial surface white to pallid, tomentose to hirsute, azonate; hymenium translucent, when young or fresh pale orange-yellow to deep orange-red when dried or in older specimens usually blood red, waxy, the folds narrow, 0.5-1.5 mm deep, continuous nearly to the margin, radiating, branching to acute side ridges or dichotomously, occasionally forming elongated and nearly rectangular pits, one or two per milli-metre; context white to pallid, up to 3 mm thick, cartilaginous and water-soaked when fresh, when dry cottony, often striated with waxy hyphal strands.
Hyphal system monomitic; context of two hyphal layers, the abhymenial layer has hyphae randomly oriented, rather loosely woven, lacking granular deposits, with interspersed waxy strands, hyaline, rather thin- to thick-walled, with clamp connections, 2-5.5 µm diam; abruptly the hyphae become closely packed, parallel, horizontally oriented, this hyphal layer extends to the subhymenium. However, at the base of the folds the hyphae are randomly oriented, serpentine, more widely spaced, becoming flexuous and loosely woven in the folds, these hyphae have walls rather thin and with hyaline, apparently gelatinous droplets up to 2 µm diam, scattered over the exterior; subhymenium and hymenium of some specimens with granular deposits throughout (Fig. 22); cystidia lacking to scattered, cylindrical or with the projecting portion slightly swollen, thin-walled, occasionally incrusted, frequently collapsed, 30-65 x 4-7.5 µm, projecting up to 25 µm; basidia of the chiastobasidium type (Boidin 1958), slenderly clavate, 17-28 x 3-5 µm; spore wall thin, hyaline, smooth, IKI-, very pale blue in lactic-blue; spores some biguttulate, cylindrical, in profile allantoid to reniform, 3.5-4.5 x 1-1.5(-2) µm (Figs. 2C and 22).
Habitat: Saprophytic on a wide variety of angiosperms and gymnosperms, associated witha white rot. Sometimes isolated from decay in living oak (Davidson et al. 1942), poplar (Atwell 1956), and wood products (Davidson et al. 1947). Common in autumn in North America from southern United States to tree line in Canada; widespread in Europe; also in Morocco (Marie and Werner 1938), Brazil, Uruguay, China, India, Japan, Siberia, Tibet, and Pakistan.
Critical specimens examined
Authentic: M. imbricatus, Tibet, Ludlow and Sheriff 12187A (now at K).
 
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