Slideshow image
Physcia subobscura Nyl.
Family: Physciaceae
Physcia subobscura image
Thompson, J., 1984. American Arctic Lichens: The Macrolichens.
Thallus small to middle-sized, the marginal lobes low lying, the central forming small tufts or cushions; lobes narrow, to 0.3 mm broad, the tips sorediate with labriform soralia, the tips then erect to reflexed, the margins ciliate with blackening cilia; upper side light gray to very dark, smooth, epruinose; underside white to brownish with black rhizinae; upper cortex paraplectenchymatous; lower cortex prosoplecten-chymatous. Apothecia laminal, sessile to short pedicillate, to 2 mm broad, disk flat, brown, bluish pruinose; epithecium brown; hymenium low, 60-70 μ, hyaline; paraphyses unbranched or branched at tips, capitate; asci clavate; spores brown, 1 septate, “physica type” with hourglass lumina, 15-18 x 9-10 μ. Conidia cylindrical 3-4 μ.

Reactions: cortex K+ yellow, medulla K—.

Contents: atranorin in the upper cortex.

This species grows on rocks in the vicinity of seashores and in the vicinity of rainwater depressions. It is probably circumpolar but reports are from Europe and North America in arctic and boreal localities. It is very rare in North America.