Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: foliose, small to rather large, 2-4(-5) cm wide, rounded or unilaterally developed, loosely adnate, distinctly and deeply lobate lobes: short to extended, 2.5-1.5 cm wide, 130-350 µm thick when moist, apically broadened, rather few, repeatedly ±furcate or palmately branched lobules: elongated, 0.5-2.5(-4) mm wide, linear, usually convex and canaliculate below; tips: often broadened and ±flat, entire or crenate, not distinctly swollen and plicate upper surface: olive-green, usually not black, dull or slightly glossy, epruinose isidia: absent or present, few or abundant, at first globose to terete, finally scale-like lower surface: concolorous or somewhat paler, with white tufts of rhizines Apothecia: often numerous, 0.5-2 mm wide, usually broader than the lobules, adnate or sessile with ±constricted base disc: plane to slightly concave or convex, smooth, reddish brown, dull or slightly glossy, epruinose thalline exciple: thin, entire or slightly crenate, inconspicuous or slightly prominent, lacking a pseudocortex proper exciple: thin, euthyplectenchymatous or sometimes subparaplectenchymatous hymenium: hyaline, 6590 µm tall asci: clavate to subcylindrical, (6-)8-spored ascospores: hyaline, ±ellipsoid with acute or obtuse ends, 2-celled, rarely indistinctly 4-celled, not constricted at septum, (8.5-)12-22(-24) x 4-7(-8.5) µm Pycnidia: laminal or marginal, immersed, pale conidia: bacilliform, with slightly swollen ends, 5-6.5 x 1-1.2 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on siliceous and calcareous rocks at low to high elevations World distribution: SW North America, the Caribbean, South America, China, India, Japan, and Socotra (Yemen) Sonoran distribution: southern and central Arizona, throughout Sonora and Baja California Sur, Chihuahua, and Sinaloa. Notes: Collema texanum's elongated, repeatedly branched, canaliculate lobes with down curved margins and its 2celled ascospores are characteristic. Tongue-shaped, canaliculate lobes are also found in Digitothyrea that may grow side by side with Collema texanum. Digitothyrea differs, however, in its jet black thallus color, its coccoid cyanobiont, and its apothecial and pycnidial characters.
Thallus olive green, usually not black (even when wet), foliose, adnate to ± loose, moderately thick; outline irregular; lobes distinct, elongated, convex, canaliculate below, repeatedly furcate with down-turned and apically broadened ends; surface smooth, dull; isidia absent, sparse or common, globular, swollen, or inflated, with age rarely ± flattened; apothecia occasional to common, sessile to barely stalked, laminal, expanded; disk deep reddish brown, flattened to slightly concave or convex; margin lecanorine, concolorous with thallus, with a broad, densely prosoplectenchymatous outer thalline exciple, and a distinct inner prosoplectenchymatous proper exciple; ascospores ellipsoid to subfusiform, with acute to blunt ends 1(-3) septate, 12-22 x 4-7 μm.
Substrate & Ecology: In the Galapagos this is currently the only Collema species known from rock (basalt lava); moderately common; typically found in the transition zone, but some specimens also from the dry and humid vegetation zones.
Distribution: New to the Galapagos; currently known from Santa Cruz, Isabela, and Santiago.
Notes: The species can typically be recognized by the convex, narrow, repeatedly branched lobes that are canaliculate below.
Selected specimens: Santa Cruz Island: Puerto Ayora, near begin of road to Baltra, 0˚44’34”S, 90˚13’27”W, 25 m, on rock (lava), 26 May 2005, Aptroot 63102. Santiago Island: along the trail from Bucanero to Jaboncillos, ca. 3 km SE of Bucanero, 0˚10’52”S, 90˚48’33”W, 362 m, transition zone; open woodland of large Bursera graveolens and smaller Psidium galapageium trees, grassland and basalt boulders, on rock (basaltlava), 22 Mar 2006, Aptroot 65411. Isabela Island: Volcán Alcedo, along the trail going up the E-slope, basalt rubble field to the SE-side of the trail and the barranco, 0˚24’3”S, 91˚2’35”W, 434 m, dry lowlands; basalt rubble field with scattered vegetation (Bursera graveolens, Zanthoxylum fagara, Pisonia floribunda, Senna pistaciifolia), on rock (basalt lava), 9 Mar 2006, Aptroot 64990, CDS no. 31570.
from: Bungartz, F. (2008) Cyanolichens of the Galapagos Islands - The genera Collema and Leptogium. Sauteria15: 139-158.