Nordin A. 1999. Buellia species with pluriseptate spores: New and unrecorded species in North America. The Bryologist 102(2): 249-264.
Thallus as a rather thin cover over other lichens and mosses, white to grayish white, usually in small patches, smooth to irregularly verrucose, sometimes almost granular. Prothallus not seen. Cortex mainly consisting of epinecral layer, not staining in LB, adjacent to short-celled, thin-walled hyphal ends slightly protruding from algal layer. Calcium oxalate crystals present throughout thallus. Apothecia abundant, first +/- immersed in the thallus, soon sessile, 0.2-1.1 mm wide, sometimes aggregated and confluent; disc black or dark brown, first flat, later +/- convex, sometimes with a whitish pruina of calcium oxalate; margin prominent at early stages, excluded in strongly convex apothecia. Proper exciple 40-80 µm thick, excipular hyphae with brown pigmented walls and rounded to slightly elongate lumina, often interspersed with crystals; pigment dissolving into a yellow-brownish solution in K present; hymenium hyaline, without oil droplets, 75-95 µm thick; epithecium brown; subhymenial layers brown, up to 275 µm thick. Paraphyses simple or branched in uppermost part, apical cells widened and with pigmented caps; asci 70-90 x 10-23 µm. Ascospores usually 3-septate when mature, with rather pointed ends (Fig. 18), the persistent part of perispore less than half as thick as the proper wall and with narrow gaps (Fig. 19), (26.0-)27.3-31.6(-33.9) x (7.9-)8.8-10.1(-10.2) µm (M = 29.5; 9.5 µm; S.D. = 2.1; 0.6 µm; n = 50). Pycnidia not seen.
Chemistry. Thallus K+ faintly yellowish, C+ orange-yellow (microscope), P+ faintly yellowish. Atranorin (minor) and one or two xanthones present, one unidentified (RI-class: A 5, B 5, C 5-6; present in eight out of 10 tested specimens) and O-methyl-trichloronorlichexanthone (in four out of 10 specimens). Norstictic acid usually present in the apothecia (found in nine out of 10 specimen).
Ecology. Buellia terricola is a terricolous or rarely lignicolous, arctic-alpine species mainly found on calciferous ground. In the Rocky Mountains, it belongs to the alpine zone, in Arctic areas of Canada it has been found as low as just above sea level. Associated species include Caloplaca spp., Cladonia spp., Megaspora verrucosa, Ochrolechia spp., Physconia muscigena, and Rinodina spp.
Distribution. Buellia terricola seems to be a rare species, outside the Canadian Arctic zone only known from a few scattered alpine localities in the Rocky Mountains, so far only once found outside Canada (in Colorado; Fig. 16).
Remarks. Material of Buellia terricola was found under the names B. geophila and B. triphragmioides in herbaria. Buellia geophila (Sommerf.) Lynge is a closely related European species with similar morphology and ecology, but with a distinct secondary chemistry, having O-methyl-trichloronorlichexanthone as its sole substance. Furthermore, the spores are slightly smoother, with a more continuous persistent perispore part. In LM a distinct ornamentation is visible only close to the spore apices (all around the spores in B. terricola). Buellia triphragmioides Anzi differs morphologically, chemically, and ecologically (see the comparisons between B. triseptata and B. triphragmioides). Other species found under the name Buellia geophila were B. insignis (Hepp) Th. Fr., B. venusta, and Dactylospora sp. Buellia insignis seems to be closely related to B. geophila, having a similar morphology, chemistry, and ecology. The spores, normally 1-septate, often have an additional trans-septum on each side of the middle septum (originating from the endospore and lacking a pigmented proper wall part (Nordin 1997), making them appear like B. geophila (and B. terricola) spores. These septa appear late in spore development: younger spores never have more than one septum. In B. geophila and B. terricola, 3-septate spores appear much ear-lier, and all septa have an inner, soon pigmented proper wall part. Buellia insignis seems to be a widespread, but misunderstood species in North America. Imshaug (1951) included it (together with B. geophila) in B. papillata (Sommerf.) Tuck., which has smaller spores, thicker thallus, and a different secondary chemistry (+/- atranorin). No North American material either of B. papillata or B. geophila was seen in connection with this study.