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

Thallus: crustose, uneven or verruculose, slightly rimose, c. 0.3 mm thick surface: white, cream-colored, pale to greenish gray, smooth or uneven, esorediate Apothecia: sessile, mostly 1-1.5 mm in diam. disc: scarlet red, often slightly brownish tinged, epruinose margin: concolorous with thallus, persistent, epruinose, smooth or crenulate, rarely flexuous exciple: red, thin epihymenium: bright red (K+ red or magenta to purple) hymenium: hyaline, 70110 µm tall; paraphyses: strongly branched and reticulate, gelatinous, with only slightly swollen apices; hypothecium: hyaline asci: clavate, 8-spored ascospores: hyaline, transversely 5-7 septate, 35-55 x 3.5-5 µm Pycnidia: immersed conidia: filiform, slightly curved, 14-16 x 0.8 µm Spot tests: thallus K+ yellow, C-, KC+ yellow, P+ yellow or P- Secondary metabolites: atranorin, placodiolic acid, russulone, either (chemotype a) without psoromic acid, or with it (chemotype b). Substrate and ecology: on bark (Acacia, Nothofagus, Quercus), in humid to arid areas World distribution: tropical to warm-temperate, Mexico, Columbia, and Australia Sonoran distribution: Sonora at 1600-2000 m. Notes: Haematomma infuscum is characterized by its smooth to verruculose, mostly pale gray thallus, sessile apothecia with scarlet red discs, 5-7-septate spores, and containing at least traces of placodiolic acid in addition to russulone. It differs from H. dolichosporum in having longer conidia, and smaller, fewer septate ascospores.