Lepra melanochlora is a species of saxicolous (rock-dwelling) crustose lichen in the family Pertusariaceae.
The thallus of Lepra melanochlora is rather thick, grey to dark grey, and usually cracked into small . Its surface is crowded with coarse, cylindrical, isidia-like that are typically 2âÂÂ3 mm tall and 0.5âÂÂ2 mm wide. These outgrowths are only rarely branched, and their tips are blunt, somewhat flattened, and paler than the rest. The papillae are often worn at the apex, exposing the white medulla, which may sometimes produce a small amount of granular soredia.
Fruiting structures are uncommon. When present, fertile warts arise from the papillae and later expand to about 2âÂÂ3.5 mm across. Each usually bears a few apothecia (often poorly developed), with one to five apothecia per papilla. The is black, 1.5âÂÂ2 mm wide, often dusted with a whitish , and may be flat to convex and somewhat irregular; it is bordered by a curved, wrinkled . The asci are 1-spored, and the ascospores are very large, typically measuring about 180âÂÂ250 à70âÂÂ130 micrometres (üm) but occasionally reaching up to 300 à200 üm, with a smooth, unzoned wall about 22 üm thick. Conidia are cylindrical, about 4âÂÂ5 à0.5âÂÂ1 üm. In a compilation of lichenized and non-lichenized Ascomycota with the largest reported ascospores, those of Pertusaria melanochlora had the largest volume: 300 à200 üm, equivalent to 0.05 cubic millimetres.
In standard spot tests, the thallus is Câ and UVâÂÂ, K+ (yellow turning red), KC+ (magenta-violet, briefly), and Pd+ (orange-red); it contains picrolichenic and protocetraric acids.