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Stereocaulon rivulorum H. Magn.
Family: Stereocaulaceae
Stereocaulon rivulorum image
Stephen Sharnoff  
Thompson, J., 1984. American Arctic Lichens: The Macrolichens.
Primary thallus disappearing. Pseudopodetia loosely or firmly adhering to the ground, erect or decumbent, forming low lax tufts, whitish with a bluish tinge 0.5-1.2 mm thick, bare or with a whitish to roseate thin tomentum, very fragile, sparingly branched with no distinct main axis; phyllocladia glaucous-white, granular or somewhat elongated, broader toward the apices, dispersed in groups along the pseudopodetia, leaving spaces showing on the axis, conglomerate and angular crustose on some decumbent pseudopodetia; cephalodia infrequent, on the underside of dorsiventral pseudopodetia, inconspicuous, tuberculiform with granular surface, of the same pale color as the tomentum or brownish violet, containing Nostoc. Central medullary hyphae parallel, not firmly conglutinate, leptodermatous, 2.5-3.5 µ thick, the lumina 1.3—1.7 µ; the exterior hyphae forming a pale yellowish cylinder of gelatinous, more conglutinate, hyphae 6-10 µ thick, colored pale yellow by KOH; phyllocladia with cortex 25-45 µ thick, pale yellowish, of firmly conglutinate hyphae, not easily discernible, partly parallel to the outer surface. Apothecia usually numerous, terminal or sublateral, 1-3 mm broad; disk dark brown, with long persistent pale margin, lower surface plane, white, tomentose; hypothecium hyaline, 35-50 µ thick; hymenium 60-70 µ thick; paraphyses contiguous, 1.5 µ thick, the tips capitate to 4.5 µ brown; asci cylindrico-clavate, 50-60 x 10-12 µ, 1+ pale blue, hymenial gelatine not colored; spores 8, cylindrico-fusiform with one end narrower, 3-septate, 25-37 x 3-3.5 µ. Conidia straight, cylindrical 5-6 X 1-1.2 µ.

Reactions: K+ yellow, P— .

Contents: 

Strain 1: atranorin, perlatolic acid, and anziatic acid. This strain occurs in Scandinavia, Iceland, Greenland, and Alaska. The similar appearing S. groenlandicum has the same content as this strain but with the addition of miriquidic acid.

Strain 2: atranorin and lobaric acid. This is the common arctic-alpine strain.

Strain 3: atranorin, stictic and norstictic acids. Lamb (1977) cites only Greenland and Jan Mayen Island for this strain.

Strain 4: only atranorin present. A widely distributed strain.

This species grows in low places below permanent snowbanks and along streams where it is occasionally inundated. It is circumpolar, arctic, and alpine, in our sector distributed from Greenland, trans-Canada to Alaska and south to Colorado and Washington.