Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: foliose, 2-6 cm in diam., adnate, irregularly lobate lobes: very irregular, thickened (swelling markedly when wet), often anatomosing, 2-4 mm wide, 150-800 µm thick; apices: rotund, thickened, entire or isidiate upper surface: usually olivaceous brown to brownish black, dull, +granular, heavily wrinkled longitudinally isidia: scattered to very dense, usually laminal but sometimes marginal, spherical or granular to subcylindrical, simple, concolorous with the thallus or darker internal anatomy: with upper and lower cortices consisting of a single layer of irregularly isodiametrical cells 4-7 µm in diam., internally with loosely interwoven chains of Nostoc and hyphae lower surface: pale to medium gray, wrinkled, with scattered tufts of white hairs Apothecia: frequent, laminal, sessile, on thickened lobe margins, 0.5-2 mm wide disc: light brown to red-brown, concave to plane margin: thalline, concolorous with the thallus, wrinkled, granularly isidiate exciple: euparaplectenchymatous, 45-90 µm thick centrally hymenium: hyaline below and thinly yellow or brown above, 90-135 µm tall; paraphyses: unbranched, 1-2 µm wide, slightly inflated apically; subhymenium: yellow to pale brown, 35-70 µm thick asci: cylindrico-clavate, 8-spored ascospores: hyaline, submuriform, 3-5-septate transversely, 0-1-septate longitudinally, ellipsoid to subfusiform, 20-35 x 9-12 µm Pycnidia: not observed Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: common on bark of soft-barked oaks at intermediate elevations in montane forests World and Sonoran distribution: relatively common in southeastern Arizona and adjacent parts of Sonora and Chihuahua, and Baja California Sur. Notes: Leptogium milligranum looks rather like a Col-lema and has a rather poorly defined cortex, but Collema species in the region have such extensively anastomosing lobes. Anatomical sections are necessary for confirmation. Due to its similar morphology L. milligranum may be the isidiate counterpart of the L. chloromelum. The former species is a common component of semi-arid oak woodlands whereas the latter species extends from the tropics into warm, temperate areas in southeastern U.S.A. Reports of L. milligranum from Ontario and India are apparently misidentifications.
Thallus black to brownish black when dry, deep olive or brownish black when wet, ± adnate, thick, swelling considerably when wet; outline orbicular; lobes indistinct and broadly merging; surface wrinkled, dull, longitudinally folded and thus strongly ridged; isidia numerous, granular, rarely ± subcylindrical; usually abundant all across thallus, especially on the thallus ridges, occasionally also marginal; apothecia not seen in Galapagos specimens.
Substrate & Ecology: On bark or wood, rarely also on rock (basalt lava), moderately common from the transition zone to the brown zone, rarely also at higher elevations.
Distribution: Known from Fernandina, Santiago, Santa Cruz, Isabela, and San Cristóbal.
Note: At first glance this species looks more like a Collema, but it cannot be easily confused with the three other Collema species currently known from Galapagos. Reports of Weber of L. isidiosellum are erroneous; all Galapagos material previously identified as Leptogium isidiosellum (Riddle) Sierk has fusing lobes and coarsely granular isidia and thus belongs to L. milligranum. The species is often incorrectly reported as L. millegranum, the correct spelling being milligranum.
Specimens examined: Fernandina Island: W-side 100 ft, Weber 314 (L-40470), COLO no. 193190. Isabela Island: Volcán Alcedo, outer E-exposed slope just below the crater rim, 0˚25’17”S, 91˚5’8”W, 1077 m, fern-sedge zone; basalt outcrops, SE-exposed slope with scattered shrubs of Tournefortia rufo-sericea, Opuntia insularis, Lantana peduncularis and occasional trees of Zanthoxylum fagara among basalt rubble, on bark of Croton, 8 Mar 2006, Aptroot 65136, CDS no. 31719; Volcán Cerro Azul, S slope above Iguana Cove, 350 m, on Scalesia, 25 Jun 1976, H. Sipman 71 (L-63546), COLO no. 297890. San Cristóbal Island: plain between Cerro Pelado and Cerro Partido, S of Ripioso, 0˚51’31”S, 89˚27’34”W, 372 m, transition zone; dense shrubland with Croton scouleri, Clerodendrum molle and Macraea laricifolia, on bark, base of Zanthoxylum fagara; shaded, wind- and rain-sheltered, 28 Apr 2007, Bungartz 6669, CDS no. 34905. Santa Cruz Island: at the North side of the island, along the dirt road to the ash quarry Mina Granilla Roja, 0˚36’56”S, 90˚22’3”W, 570 m, lower transition zone; dry, semi-deciduous forest with Bursera graveolens and Zanthoxylum fagara, on dead wood on the ground, 23 Feb 2006, Bungartz 3894, CDS no. 27776; barranco behind Darwin Station, on Bursera, 21 Jun 1971, Weber s.n. (L-54821), COLO no. 255249. Santiago Island: Santiago Bay, Dawson s.n. (L-41036), COLO no. 192948.
from: Bungartz, F. (2008) Cyanolichens of the Galapagos Islands - The genera Collema and Leptogium. Sauteria15: 139-158.