Syst. Lich. Germ.: 420 (1855).

Thallus slate gray to grayish black when dry, olive when wet, foliose, adnate, papery thin; outline ± orbicular; lobes distinct, elongate, ± broadened and flattened, regularly spreading (fan-shaped); surface smooth to barely striate, dull, but not distinctly wrinkled; isidia numerous, quite variable in shape and size, either cylindrical and typically becoming branched, or becoming flattened, scale-like or lobules (phyllidiate), abundant across the thallus surface, but occasionally also along the thallus margin; apothecia rare, sessile to shortly stalked, laminal, expanded; disk pale to deep reddish brown, initially concave, flattened or indistinctly convex with age; margin lecanorine, typically pale, cream colored, rarely concolorous with the thallus, entire or isidiate, with a broad paraplectenchymatous outer thalline exciple and an inner, indistinct, thin, prosoplectenchymatous proper exciple; ascospores ellipsoid to fusiform, typically transversely 3-septate, rarely becoming submuriform with the formation of an additional longitudinal septum, 19-24 x 6-12 μm.

Substrate & Ecology: A very common epiphyte, occasionally epiphyllic (fern fronds, large leaves), less common on plant debris, rarely on soil (humus), occasionally also on rock; throughout the humid vegetation zones of islands with higher elevations, most typical in the Scalesia-zone, but also in the brown zone, the Miconia-zone, the fern-sedge zone and throughout the agricultural areas of inhabited islands.

Distribution: One of the most common species of Leptogium in the Galapagos; currently known from Santa Cruz, Isabela, Santiago, Pinta, and San Cristóbal Island.

Notes: Easily recognized as a broad lobed species with abundant isidia, rarely also with apothecia. Similar in size and overall appearance to the non-isidiate L. azureum and Swinscow & Krog (1988) suggested that the two taxa form a classical species pair.

Selected specimens: Isabela Island: Volcán Alcedo, outer SE-exposed slope, ca. 500 m below the crater rim, 0˚27’13”S, 91˚5’46”W, 1035 m, fern-sedge zone; Paspalum conjugatum with scattered shrubs of Tournefortia rufo-sericea, on bark of Tournefortia, 6 Mar 2006, Aptroot 64845, CDS no. 31421; on crater rim SE of hut, 0˚27’35”S, 91˚6’43”W, 1080 m, fern-sedge zone; tortoise pasture with scattered trees (Tournefortia rufo-sericea, Zanthoxylum fagara), on bone, carapace of living tortoise shell, 5 Mar 2006, Aptroot, 64823, CDS no. 31398; Pinta Island: along the trail up to the summit from the S-coast, 0˚34’39”N, 90˚45’7”W, 436 m, brown zone; dense forest of Zanthoxylum fagara, few Pisonia floribunda, and the vine Cissampelos pareira; Justicia galapagana in understory, on bark, twigs of Pisonia floribunda (ca. 2 cm in diam.); shaded, wind- and rain-sheltered, 26 Feb 2007, Bungartz 5802, CDS, 33475. San Cristóbal Island:, along trail between entrance to Cerro Pelado and Cerro Partido, trail to Ripioso, 0˚51’40”S, 89˚27’38”W, 383 m, transition zone; dense forest on abandoned farmland with old trees of Hippomane mancinella and introduced species such as Psidium guajava, Passiflora sp. and an understory of Chiococca alba and Rubus niveus, on rock, E-exposed slope of small basalt rock; shaded, wind- and rain-sheltered, 28 April 2007, Bungartz 6687, CDS no. 34923; Santa Cruz Island: along the road from Bellavista to Los Gemelos, 0˚37’55”S, 90˚23’33”W, 579 m, Scalesia zone; open Scalesia pedunculata forest with Rubus niveus, Psychotria rufipes, Zanthoxylum fagara, and scattered lava boulders, on bark, fallen trunk of Scalesia (ca. 15 cm in diam.); semi-shaded, wind- and rain-sheltered, 12 Feb 2006, Bungartz 3484, CDS no. 27240; Tras del Puntudo, ex finca de Don Benito, 0˚38’23”S, 90˚19’57”W, 732 m, Zona húmeda, sobre corteza, Scalesia penduculata, altura al pecho, 8 Feb 2007, Nugra 388, CDS no. 35143; vicinity of Academy Bay, trail to La Copa, moist zone, tree trunks, Weber 83 (L-40275), COLO no. 190021. Santiago Island: along the trail from Cerro Gavilan to La Central, 0˚13’2”S, 90˚46’33”W, 890 m, moist upland; artificial grassland caused by former grazing with Setaria parviflora, Cyperus virens, Paspalum galapageium, Pityrograma calomelanos var. calomelanos, Rhynchospora nervosa, Doryopteris palmata, Hyptis rhomboidea and open soil, on soil between pasture grasses, on NW-exposed and ca. 10° inclined slope; sunny, wind- and rain-exposed, 24 Mar 2006, Bungartz 4835, CDS no. 29009; along the trail from the caseta in La Central to La Bomba (at the coast), ca. 2.5 km NE of the caseta, 0˚13’41”S, 90˚44’9”W, 528 m, transition zone; open woodland of Psidium galapageium, Zanthoxylum fagara, Bursera graveolens, Trema micrantha and Opuntia galapageia with shrubs of Clerodendrum molle, on bark, branches of Pisonia floribunda; semi-shaded, wind- and rain-sheltered, 25 Mar 2006, Bungartz 4881, CDS no. 29085.

from:
Bungartz, F. (2008) Cyanolichens of the Galapagos Islands - The genera Collema and Leptogium. Sauteria 15: 139-158.

Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Thallus: foliose, 1-5(-8) cm in diam., adnate, subdichotomously to irregularly lobate lobes: irregular, elongate, +plane to slightly roughened (but not wrinkled), separate, 2-4 mm wide, 35-110µm thick; apices rotund, entire, dentate to irregularly cut and isidiate, occasionally upturned upper surface: light to medium gray, usually dull, smooth to somewhat wrinkled isidia: usually dense, laminal to marginal, usually cylindrical to flattened and may become lobulate, simple but usually becoming branched, concolorous with the thallus or darker internal anatomy: with upper and lower cortices consisting of a single layer of irregularly isodiametrical cells 5-8 µm in diam., internally with loosely interwoven chains of Nostoc and hyphae lower surface: light to medium gray, smooth, with scattered tufts of white hairs Apothecia: occasional, laminal, sessile to substipitate, 0.5-2 mm wide disc: light brown to more usually red-brown, slightly concave to plane to convex margin: thalline, concolorous with the thallus or cream-colored, entire or isidiate exciple: euparaplectenchymatous, often poorly developed centrally hymenium: hyaline below and thinly brown above, 95-130 µm tall; paraphyses: unbranched, c. 1 µm wide, slightly inflated apically; subhymenium: pale yellow, 45-80 µm thick asci: cylindrico-clavate, 8-spored ascospores: hyaline, 3-septate transversely, 0-1-septate longitudinally, ellipsoid to fusiform, 18-23 x 6-10 µm Pycnidia: not observed Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: particularly common on bark of soft-barked oaks and junipers at intermediate elevations World distribution: pantropical and pantemperate, throughout North America, especially in the south, Australasia, Europe, Asia and East Africa Sonoran distribution: central and southeastern Arizona, Sinaloa and Baja California Sur. Notes: Morphologically the bluish gray L. cyanescens is most similar to the olivaceous brown L. dactylinum Tuck. in Nyl., that is not yet known from the Sonoran region. The latter species usually has smaller, more squamiform lobes and is more abundantly fertile than L. cyanescens.