Magnusson, AH. 1939. Studies on Species of Lecanora, Mainly the Aspicilia gibbosa Group. Kongl. Svenska Vetenskapsakad. Handl. 17: 34-35.
Thallus determinate, uniform, or distinctly zonate in outline, pale ashy gray or ashy gray, rimose-areolate, areoles irregular and unequal, subcomposite, KOH-, outline thin and surrounded by dark hypothallus. Apothecia crowded, single or often a few in any areole, minute, disc black, plane, impressed, surrounded by often not darker thalline margin. Hymenium tall, paraphyses submoniliform. Excipulum iodine not bluish. Spores moderately sized.
Thallus 2-4 cm diam., C.U.C. 233, 495, 554, 590, areolae 1-2 mm large, 0.3-0.4 mm thick with irregular and wide cracks to the base, gradually dividing into smaller ones, their surface uneven with low protuberances and initial cracks (Fig. 19). - Cortex 15-20(35) µ thick, +/- transparent or partly obscured by air, exterior 4-8 µ brownish-olive, no or little developed amorphous stratum. Cells +/- distinct, 3-5(6) µ, thin-walled, subangular. Gonidia 8-12(17) µ, stratum 35-50(100) µ, sometimes with enclosed air, dense, surface even. Medulla +/- transparent or gray and filled with much air, cellular, dense, cells thin-walled at the base and especially below the apothecia with much oil.
Apothecia De 125-240, (1)2-5 present in most areolae, disc 0.25-0.4(0.8) mm, often irregular in shape, smooth, plane or +/- concave, thallus margin generally obsolete and gray, rarely slightly prominent and darker than the thallus. Apothecia 170-250(300) µ deep. Exciple +/- distinct, widened, about 35 µ, towards the surface with globose or angular, distinct cells, brownish or olive, about 35 µ deep, laterally 10-15 µ thick, at the base up to 35 µ +/- distinctly cellular, I-. Hypothecium 35-50(90) µ thick, cloudy, indistinctly cellular, I+ bluish. Hymenium (110)135-150(170) µ high, I+ yellowish- or orange-brown; upper 15-20 µ dirty olive green. Paraphyses +/- indistinct in water and HCl non-guttulate, in KOH distinct and much branched, apices submoniliform, uppermost two cells globose, 2.5(3) µ, next joints (broadly) ellipsoid, lower ones cylindric. Asci 100-120 X 17-25 µ, clavate. Spores 8, (17)20-25 X 13-16 µ, broadly ellipsoid to ovoid.
Pycnidia as brown prominent warts about 140 X 100 µ, wall thin, brownish. Conidia 17-20 X 0.6-1 µ, straight, partly relatively thick, 1 µ.
Habitat. On siliceous rocks, at the banks of brooks or in other places rich in nitrogen. One specimen (Funasdalen) associated with Caloplaca conf. ferruginea, Rhizocarpon badioatrum, Lecanora polytropa, Lecidea goniophila, Candelariella vitellina and traces of Lecanora (Plac.) muralis and L.(Asp.) cinereorufescens, probably growing near the top of a stone.
Distribution. This hitherto neglected species has probably a wide boreal and perhaps arctic distribution. Norway. Finnmark: Varanger, Nyborg 1857 TH. FRIES (U.), type.--Sweden. Jämtland: Åre, Mörviken 1936; Duved, Prästgården 1933 STENHOLM (in hb). Frostviken, Raudek 1934 Mn, at 400 m on stones in a brook.—Finland. Ostrob. bor.: Nedertorneå, Kaakamo, Udden 1915 E. HÄYRÉN (Hfs.) on the shore on stone. Thallus distinctly radiate, zonate.—Novaja Zemlya. Belusha 1921 LYNGE (O.) called L. gibbosa by ZAHLBR.—Greenland. South east part: Marias valley 1932 P.F. SCHOLANDER (O.) called L. arctica v. composita by LYNGE. Distinctly zonate.
The new speices has a rather commonplace appearance, most resembling L. obscurata though with thicker, cracky thallus and several not prominent apothecia in the areola. Some specimens resemble L. sonata on account of the zonate thallus margin, but the thallus there is thinner with prominent apothecial verrucae, and the cortical cells smaller. L. laxula has about the same colour but denser not impressed discs, lower hymenium and short conidia. L. indissimilis is characterized by its large cortical cells, its high hymenium, impressed discs, rather large spores and long conidia.