Thallus: fruticose, attached by a holdfast; main branches: complanate to broadly complanate; terminal branches: complanate to terete, often anastomosing, up to 1 mm thick and up to 10 mm broad, with or without complanate lateral ecorticate branchlets lobe surface: brown to creamy gray, smooth with a thin white pruina; holdfast only as an attachment; prothallus: not seen cortex: with verrucose or smooth, hyaline or brown hyphae, 50-80 µm thick; epicortex: the uppermost 2-3 µm, granular, hyaline medulla: white, byssoid, without thallus gel; hyphae: hyaline, forming a loose network oriented in all directions Ascomata: 0.3-1.5 mm diam; epithecium: 25-45 µm; hymenium: 100-120 µm high; paraphysoids: sparsely branched, hyaline, c. 1 µm in diam.; hypothecium: 200-300 µm, only rarely extended into medulla asci: clavate, 70-80 x 15-18 µm ascospores: fusiform, (17-) 20-24 (28) x (4-) 6-8 (-9) µm Pycnidia: black, solitary, lateral, immersed, often in low, warty protuberances, 0.1-0.3 mm diam conidia: filiform, (8-) 10-12 (-16) x < 1 µm Spot tests: thallus K-, C-, KC-, P+ orange Secondary metabolites: fumarprotocetraric acid, protocetraric acid and succinprotocetraric acid, one unknown depside and one other unknown substance. Substrate and ecology: locally abundant on various trees, shrubs and cacti as well as on cliffs and rocks near the ocean, but above the littoral and well away from direct salt spray World and Sonoran distribution: restricted to the west coast of North America in Baja California, Sonora, Sinaloa and southern California. Notes: The major morphological differences between Dendrographa leucophaea f. leucophaea and D. leucophaea f. minor are that the latter has shorter internodes, frequent lateral branchlets and lacks ascomata. Old herbarium material contains few transitional forms between Dendrographa leucophaea f. leucophaea and D. leucophaea f. minor, probably due to selective collecting. In the field, though, it is rather easy to find transitional forms. Hypothesized transitional forms include specimens: a) with ascomata, main branches with short internodes and many lateral branchlets; b) with or without ascomata, some main branches with short internodes, carrying many lateral branchlets and some main branches with longer internodes and ± without lateral branchlets; and c) with or without ascomata, main branches with long internodes and with few and small lateral branchlets. Dendrographa leucophaea f. leucophaea and D. leucophaea f. minor have been observed growing from the same holdfast, suggesting that an individual can change morphology from one branch to another. On the basis of the observed gradient populations Sundin and Tehler (1996) proposed that Dendrographa leucophaea f. minor consists of clonal populations of D. leucophaea formed by fragmentation of branchlets. That hypothesis was recently corroborated by molecular data (Lohtander et al. 1998).