Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: at first forming small, decumbent rosettes, but soon developing small, fruticose cushions up to 6 mm wide, branches: cylindrical to slightly flattened, irregularly to ±dichotomously branched, fan-shaped or fingerlike, 1-3 mm long, 0.15-0.65 µm thick, centrally with loose, fountain-like hyphal strand of 3-5 rows incorporating a few photobiont cells upper surface: black, dull or slightly glossy, usually isidiate isidia: numerous, globose to short cylindrical, sometimes branched, 0.025-0.05 x 0.025-0.03 mm lower surface: concolorous with the upper surface, attached by tufts of rhizohyphae Apothecia: thallinocarpous, terminal on tips of branches, up to 1 mm wide, ±round, convex, occasionally concave disc: rough, concolorous; margin: thalline, up to 80-95 µm wide; proper exciple: lacking hymenium: hyaline, IKI+ blue rapidly turning wine red, ±continuous but with wedge-shaped packets of sterile thalline tissue intruding between groups of asci, 95-110 µm tall, covered by ±continuous layer of sterile thalline tissue interrupted only by protruding asci; subhymenium: hyaline, continuous, 95-100 µm thick, IKI+ blue ascus: (16-)24-spored ascospores: hyaline, simple, broadly ellipsoid to subglobose, small, 4.5-5.5(-7) x 3-4 µm Pycnidia: terminal or subterminal, often superimposed, globose to broadly pyriform conidia: bacilliform, 2.5-3.5 x c. 1 µm Spot tests: all negative Secondary products: none detected. Substrate and ecology: on siliceous rock World distribution: North America Sonoran distribution: central and SE Arizona and Baja California Sur. Notes: The species exhibits some variation is growth habit. The specimens from Upland Sonoran Desert habitats form small cushions composed of erect branchings with usually abundant globose to short cylindrical isidia. In Baja California adpressed rosettes or cushions with terete to flattened, irregularly dichotomously or palmately branched, slender branchings predominate and isidia are usually lacking. In Lichinella stipatula and L. robustoides the branchings are always terete and more narrow. Both species lack any isidia. The former species further differs in the presence of a thin, fountain-like hyphal strand composed of 1-2 rows. In Lichinella flexa the lobes are terete, densely branched with deflexed tips and there is a distinct, compact, fountain-like central hyphal cord. Since fruiting bodies are rarely observed it may be difficult to separate Lichinella americana from other dwarf-fruticose members of the Lichinaceae.