Lepra excludens (Nyl) Hafellner

 

=Pertusaria excludens Nyl.

    Thallus crustose, rather thick, markedly cracked and areolate, areoles angular, 0.2-0.5 mm across, flat or slightly convex, papillate, white-greyish, dull white, pale grey-ochre sometimes tinged with pink when exposed to seaspray, (see Lepra excludens forme rose), prothallus concolourous, inconspicuous, often with a minute bulge at margin when merging with other thalli, soralia abundant, 0.6-1.5 mm, arising from openings of rounded warts or tubercles, coarsely granular, filled with soredia, paler than the thallus or slightly yellowish when dry and greenish when moist. Apothecia scarce, hidden and arising from the soredia, often aborting. Ascospores unknown. Soralia: C-, K+ yellow > blood-red, KC+ yellow > red, Pd+ yellow-orange. On siliceous (granite) rocks in coastal areas, very seldom on rocky ridges inland (possible confusion with  Pertusaria lactescens ?). N.B. Possibly the sorediate morph of Lepra monogona that is much more scarce. See, notably far from the coasts, Pertusaria lactescens of which the chemical reactions are identical, but  with a thinner thallus and smaller isidioid-like soralia, scattered all over the thallus and not restricted to top of warts.