[Placynthium subnigrum B. de Lesd., more]
Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: dwarf-fruticose, often forming spreading "crusts" cushions: 1-3 mm wide, up to 1.5 mm high, composed of erect, furcate, cylindrical branchings: branches 0.5-1mm long, 0.1-0.2 mm wide, tips often pointed, centrally with rather compact central hyphal strand, 100-140 µm thick, anatomy reticulate towards the periphery, 30-50 µm thick upper surface: black, usually glossy, rarely dull isidia: absent, but the small branches may appear isidioid lower surface: concolorous, attached by tufts of rhizohyphae Apothecia: stipitate on lobe tips, 0.4-0.75 mm wide disc: black, at first slightly depressed, finally plane and wide open; thalline margin: persisting, 75-100 µm wide, usually prominent, later flat; proper exciple: lacking epihymenium: indistinct but upper parts of hymenium reddish brown hymenium: IKI+ deep blue, 75-110 µm tall; sub-hymenium: hyaline, IKI+ blue, up to 80 µm thick, elongated as a stipe into central strand asci: clavate, thin walled, IKI- but with rather conspicuous gelatinous cap, 8-spored ascospores: biseriate, hyaline, simple, broad ellipsoid, small, 7.5-10(-12.5) x 5-6 µm Pycnidia: immersed, ellipsoid, 100-175 µm wide, simple conidia: large, filiform, falcate to sigmoid, 25-35 x 1 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on siliceous and, more rarely, calciferous soil, occasionally on soft rock, in open or sheltered situations from sea level to c. 1500 m elevation, from desert scrub to pine-juniper woodlands, absent in densely forested habitats above 2000 m World distribution: SW North America Sonoran distribution: central, southern and SE Arizona, southern California, and Baja California. Notes: The North American records of Peccania coralloides (Schultz 16076b) reported by Schultz et al. (2001: 117) and Schultz and Büdel (2003: 153) as well as the records of P. fontqueriana (Schultz 16006b, 16127) reported by Schultz and Büdel (2002: 51, 2003: 153) belong here. Peccania subnigra differs from P. tiruncula in having erect, regularly cylindrical branches forming glossy cushions, in colonizing soil crusts and in having slightly larger, broad-ellipsoid ascospores. A hypertrophic form was observed in sand-filled depressions on limestone boulders in central Arizona. This form agrees in all aspects with typical specimens of Peccania subnigra except for its lobe size. The branches are 1-2 mm long and 0.2-0.35 mm wide. Relationships with taxa from the Near and Middle East regions, as well as inner-Asian semi-desert and steppe areas, deserve further study. Peccania texana (Tuck.) Wetmore most probably belongs here.