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Heterodermia tremulans (Müll. Arg.) W.L. Culb.

Family :


W. Culberson, Bryologist 69: 485. 1966

Basionym: Physcia hypoleuca var. tremulans Muller Argoviensis, Flora 66: 277. 1880

ID :


Thallus :

Foliose, orbicular to irregularly spreading, adnate to loosely adnate, 2–7 cm wide, often coalescing and forming colonies to 15 cm wide

Lobes :

0.7–1.5 mm wide, plane to slightly convex, sublinear, ± flexuose, sympodial to subdigitately branched, usually discrete at the periphery, radiating; apices not ascending, with short lateral lobes, eciliate

Upper Side:

Grayish white to gray to brownish gray, ± darker at the apices, pruinose or not

Isidia :

Sorediate; soralia whitish or grayish, granular, forming labriform soralia at the tips of the main and lateral lobes

Lower Side :

Corticate, whitish to pale brown, rarely dark gray in the center. Lower surface rhizines sparse, mostly simple or sparsely branched, marginal rhizines frequent, concolorous with the thallus or becoming dark or black near the apices, irregularly branched, to 1 mm long, projecting beyond the lobes

Medulla :


Rare, laminal, sessile to sub stipitate, 1–3 mm wide; margin initially crenulate, becoming sorediate; disc concave, brown to brown-black, epruinose

Apothecia :

Pachysporaria-type, ellipsoidal, 23–32 × 12–14 μm. Pycnidia immersed or slightly protruding; conidia bacilliform, 4–5 × 1 μm

Ascospores :

Cortex K+ yellow, C–, KC–, P+ yellow; medulla K+ yellow, C–, P– or P+ pale yellow; containing atranorin (major), zeorin (major), 16β-acetoxyhopane-6α,22-diol (major), 6α-acetoxyhopane-16β,22-diol (major), 6α,16β-diacetoxyhopane-22-ol (minor), leucotylin (minor), chloroatranorin (minor)

Chemistry :

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