Varicellaria lactea (L.) Schmitt & Lumbsh =Pertusaria lactea (L.) Arnold

    Thallus crustose, widespreading, to 15 cm diam., rather thick, slightly rugose, pleated and rimose, areolate and slightly verrucose, whitish, pale white-cream, white-grey, homogenous and more or less globose soralia covering the thallus, to 2 mm diam., whitish, tinged greenish when moist, and C+ bright red, becoming more flattenned and marginate when old, margin sometimes distinctly pearl necklace-like, prothallus sometimes markedly developed, whitish with a more or less zonate structure. Apothecia very scarce, 1 or 2 per fertile wart (resembling to soralia), 0.4-0.7 mm diam., disc whitish due to pruine at first, then brown-pink. Ascii 1-spored. Ascospores simple, very large, 180-240 x 60-100 µm. Photobiont: Chlorococcoid. Thallus C+ carmine (sometimes faint), K-, KC+ red, Pd- ; soralia: C+ bright carmine red. Not especially maritime, on well-lit large siliceous rocks near the seashore and elsewhere. See Pertusaria hemisphaerica of which the thallus is not rimose, that seldom grows on rocks and has larger, more spherical, cream soralia, and not marginate when old.*