Magnusson, AH. 1939. Studies on Species of Lecanora, Mainly the Aspicilia gibbosa Group. Kongl. Svenska Vetenskapsakad. Handl. 17: 34-35.
Thallus up to 3 X 3 cm large, continuous, very thin, 0.15-0.22 mm, dark gray with a bluish shade, C.U.C. 515, 544, repeatedly zonate at the circumference with 1-2.5 mm broad zones, where the whitish hypothallus is +/- visible, radiately and very minutely cracky, slightly uneven; the centre smooth, very thinly rimulose, the indistinct, angular areolae 0.2-0.4 mm, plane, opaque, KOH- (Fig. 36).—Cortex 25(-35) µ thick, +/- transparent, upper 5-7 µ distinctly reddish-brown, cells +/- distinct, (3)3.5-4.5(5) µ, moderately thin-walled, hyphae distinctly branched, cells +/- discrete. Gonidia 6-8(10) µ, stratum about 40 µ thick but only small parts seen. Medulla cellular, dense, with +/- crystals from the stone; oil-cells only at the base, +/- numerous.
Apothecia numerous towards the centre, forming prominent verrucae, 0.3-0.4(0.5) mm large, De 160-180, disc deeply impressed, plane or concave, blackish, circular, or rarely 2(3) contiguous, partly slightly pruinose, margin prominent, obtuse, somewhat darker than the thallus.—Apothecia about 150 µ deep. Exciple widened at the surface, up to 50 µ broad, olivaceous brown, 35-50 µ deep, with large, rounded cells, at the base 10-15 µ, I+ indistinctly or pale blue. Hypothecium about 35 µ, cloudy, with very small cells, I+ pale blue. Hymenium 85-95 µ high, I+ sordid yellowish-green; upper 16-18 µ olive-brown, surface uneven. Paraphyses +/- distinct in water, guttulate, thin-walled with oblong cells in the lower part, in KOH discrete, 1.7 µ thick, submoniliform, apices 3(3.5) µ, subglobose or broadly ellipsoid, next cells mostly oblong, often 4-6 X 1.7-2 µ. Spores 8, shrunk in water, 17 X 9-10 µ, in KOH 18-20 X 11-14 µ when fully developed.
Pycnidia searched for in vain.
Habitat. On porphyreous rock with another zonate species (conf. L. cinerea).
Locality. Sweden. Dalarne: Särna on the shore of Särnasjön 1807 SWARTZ (R.), one large and two small parts of specimens.
This species is characterized by its very thin, zonate thallus with prominent, very small fertile verrucae, its negative K-reaction, its indistinct exciple and thin-walled, submoniliform paraphyses. The cortical structure reminds of the L. laevata but this species has a yellow K-reaction and well developed exciple. I have seen no other similar specimen in the whole material examined.
There are two other similar but sterile species present, also distinctly radiate, one K+ red with rather large, pale areolae and one K- with very dark and very small and convex areolae.The latter resembles morphologically completely the specimen associated with the authentic specimen of L. perradiata, Konyambay, but there the specimen is K+ red.