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Lepraria crassissima (Hue) Lettau |
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Nomenclatural data
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Feddes Repert. 61: 125 (1958).—Crocynia crassissima Hue, Bull. Soc. Bot. France 71: 393 (1924).
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Morphology
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Thallus crustose, leprose, with cottony to powdery or membranous appearance; bluish, greyish or greenish, brownish patches of dying parts often present; thick, relatively soft, sometimes weakly attached to the substrate; shape usually rosette-forming, uneven, often folded, usually several cm in diam.; margin usually delimited, lobes sometimes present, poorly defined; cortex absent; medulla present, very thick, white; lower surface distinct, folded (if whole thallus folded), smooth to tomentose, white to brownish; prothallus absent; areoles absent; squamules absent; often eroded patches with exposed medulla on older specimens, soredia abundant, mostly coarse, up to 300(–400) µm in diam., loosely packed; projecting hyphae present, short to long; large granules slightly resembling isidia that become sorediate may be present in well developed thalli. Photobiont green, coccoid.
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Chemistry
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Divaricatic acid, nordivaricatic acid (major, rarely trace), zeorin ± (major to minor). K–, C+rose-red, KC–, Pd–.
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Remarks
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Species producing divaricatic acid and zeorin include L. crassissima, L. incana and L. nigrocincta, but differ in following aspects. L. incana and L. nigrocincta contain nordivaricatic acid in trace amount or it is absent, unlike L. crassissima. L. incana is mostly composed of soredia (powdery), lower surface not distinct, thallus never folded and rarely delimited. L. nigrocincta has cottony appearance like L. crassissima, but develops dominant blackish hypothallus and partly scarce soredia. Additionally, Baruffo et al. (2006) reported divaricatic acid in L. rigidula as a very rare accessory. That species is distinct by its lax cottony thallus and very long projecting hyphae from soredia, and producing atranorin and nephrosteranic acid.
L. multiacida, L. lobificans, sometimes L. nivalis, L. vouauxii may be morphologically similar, but differ in chemistry and spot reactions spot reactions (see descriptions of these species). L. isidiata was historically described as variety of L. crassissima, but today is defined differing in chemistry, morphology, ecology (see L. isidiata). L. crassissima was synonomised with L. incana by Kümmerling et al. (1991, Leuckert et al. 1995), but was shown to be distinct by van den Boom et al. (1994), Ekman & Tønsberg(2002). Species producing isidia-like structures include L. crassissima, L. isidiata, L. santosii, L. xerophila, see the discussion under L. isidiata
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Ecology and distribution
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Substrate and ecology: mostly siliceous rock and epilithic mosses, sometimes bark or calcareous rock; shaded, humid. Distribution: Europe, Australia.
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