Varicellaria lactea

Thallus wide-spreading, rather thick, white to grey-white; prothallus paler, often ± zoned; upper surface smooth or ± roughened, matt, mostly rather regularly rimose-areolate; areoles coarse, 0.3–0.8 mm diam., flat to strongly convex, irregularly rounded or angular; soralia 0.5–1.5 mm diam., white, ± convex, at times surrounded by a fragile thalline collar, occasionally ± efflorescent, mostly discrete, rather widely but evenly scattered, rarely contiguous; soredia (50–) 100–160 (–220) µm diam., sometimes aggregated into consoredia. Fertile warts 0.4–0.5 (–0.7) mm wide, very rare, soralium-like, mostly with 1 (-2) apothecia; disc pale brown, at first white-pruinose, often surrounded by an irregular sorediate thalline exciple. Asci 1-spored. Ascospores 180–240 × 60–100 µm, walls very thick (8–10 (–33) µm), not laminar or striate. Conidia 4.5 × 0.5 µm, cylindrical. Thallus C+ carmine-red, K–, KC+ red, Pd–, UV± faintly glaucous (lecanoric and variolaric acids).

Characterised by the white-grey, areolate thallus with neat, round, ± convex, white, C+ bright red soralia; V. hemisphaerica, which is also C+ red, has a pale blue-grey thallus with paler, but not white, markedly convex soralia and usually occurs on trees. Lepra excludens is broadly similar in thallus and soralia, but is C–.