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Plectocarpon lichenum (Sommerf.) D. Hawksw.
Family: Lecanographaceae
[Arthonia stictarum (De Not.) Jatta,  more]
Plectocarpon lichenum image
Ascomata: developing on the upper or lower surface of the host thallus, inducing distinct, basally constricted galls, dispersed, single or more rarely grouped, black, flat to convex, rarely slightly concave, rounded, 0.6-4(-5) mm diam., c. 140-340 µm thick; surface slightly shiny or mat, smooth to minutely warted; warts of 55-150(-190) µm diam. stroma: multilocular; loculi c. 70-160 µm wide; sterile stromatic tissue dark greenish (but appearing olivaceous owing to other brown pigments), K+ green intensifying, N+ orange to reddish brown; pigment not granulose, dissolving at high concentration; layer below the stroma reddish brown, consisting of host cortex over which the ascomata are growing hymenium: hyaline, sometimes partly greenish brown, K+ greenish (owing to the greenish black stromatic pigment), soon becoming bright yellow to almost orange (additional pigment of the hymenial gel?), entirely filling the loculi, 80-105 µm high, I+ red paraphyses: richly branched and anastomosing, 2-2.5 µm thick, apically slightly enlarged asci: clavate, (4-)6-8-spored, 55-75 x 14.5-17.5 µm ascospores: hyaline, becoming brown, K+ greenish when overmature, oblong, 3-septate, often slightly constricted at the septa, (16-)18.5-21.3(-23) x (5-)5.3-6.3(-7) µm, l/w ratio 3.1-3.8 (N=96); perispore hyaline, 0.5-1.5 µm thick, becoming uniformly brown when overmature Pycnidia: immersed in the stroma, wall dark brown, irregular, 40-50 µm wide, 80-90 µm high conidia: 4.5-5.5 x 1 µm. Hosts: in the Sonoran area, on Pseudocyphellaria anthraspis; elsewhere mainly on Lobaria pulmonaria, rarely on Pseudocyphellaria anomala World distribution: Africa (Kenya, Tanzania), La Réunion, North America (Canada: British Columbia, U.S.A.), Asia (Russia, Turkey), Europe and Macaronesia. Sonoran distribution: known from one specimen in California somewhat north of the Sonoran region.