Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: fruticose, short, stubby strongly inflated blades, generally unbranched branches: composed of cylindrical blades 2-3(-4.5) mm in diam. and up to 3 cm in length surface: pale green, becoming greenish yellow in herbaria, often basally blacked, smooth or occasionally crumpled cortex: smooth to gently ridged, rigid, breaking when a branch is bent medulla: white, cottony, lacking the aggregations of hyphae in N. homalea, fide Spjut (1996) "...like tissue paper, hyphae in short bundles and in a triangulate lattice" Apothecia: common, primarily terminal, either solitary or in clumps, up to 6 mm in diam. disc: white or pale buff, concave to convex asci: clavate, 8-spored ascospores: hyaline, 1-septate, fusiform to oblong, 10-12 x 3-5 µm Pycnidia: black, immersed conidia: straight, rod-shaped Spot tests: negative, except when K+, P+ indicating the presence of salazinic acid Secondary metabolites: (-)-16α-hydroxykaurane, +zeorin (usually present), terpenoids, +salazinic acid and, fide Spjut (1996), T3 triterpene. Substrate and ecology: on coastal rocks sharing microhabitat preferences with N. laevigata and N. procera World and Sonoran distribution: coastal California from the Mexican border to the San Francisco area, and NW Baja California, including Guadalupe Island. Notes: Niebla robusta is comprised of clumps of stubby, strongly inflated, cylindrical branches. Just as N. ceruchoides resembles a compact, tiny Cladina, N. robusta is superficially like a Dactylina because of its tubular, stunted appearance. The cortex is smooth or gently ridged, and consists of a palisade layer overlying a supportive layer. The medulla is white, and apothecia are commonly terminally borne either as solitary structures or in clumps, often triplets. Subterminal black pycnidia occur in many thalli, decreasing basally, but are absent from some specimens.