Thallus: placodioid, rosette-forming, 1-1.5 cm in diam., rimose-areolate centrally, closely appressed, thin (0.1-0.3 mm); prothallus: absent areoles: contiguous, irregularly angular to rounded or crenate, plane to somewhat convex or uneven, 0.3-1 mm across lobes: contiguous, separated mostly by incomplete cracks, plane (to occasionally strongly convex), up to c. 2 mm long, 0.5-1.5 mm wide, entire and rounded or partly crenate-incised, ultimate segments 0.3-0.7 mm wide, distinctly set off from the substrate near the tips surface: light grayish to yellowish brown, mottled with white, especially on marginal lobes pale brownish gray or slightly yellow when wet, dark grayish yellow near lobe tips, partly pruinose upper cortex: outer 5 µm hyaline; inner part pinkish gray, interspersed with refractive granules (insoluble in K) especially in upper part towards lobe tips, uniform but cells not distinct even in microtome sections stained with cotton blue, 20-40 µm thick medulla: white but lower part sometimes pale red, dense, filled with coarse, hyaline, refractive granules (insoluble in K), with thin-walled hyphae 2-4 µm wide and with lumina 1-1.5 µm wide and with cells 4-8 µm long; algal layer: continuous, with non-refractive tissues, 3035 µm thick; algal cells: 10-15 µm wide, often clumped lower cortex: indistinct except near tips, non-refractive Apothecia: common, adnate, soon becoming narrowly sessile, crowded in thallus center, up to 1.2 mm in diam. disc: dark reddish brown, medium to dark yellowish brown, dark brown, or brownish black, plane to slightly concave, at first bluish pruinose, appearing grayish brown to white, then soon naked margin: white, +level with thallus, persistent, c. 0.1 mm wide, entire to sinuous or becoming crenulate towards inside, without a parathecial ring amphithecium: present, with algae filling most of the margin and forming a continuous but uneven layer (c. 100 µm thick) below hypothecium, without granules or crystals in the medulla, corticate; cortex: c. 20 µm thick, interspersed with fine brownish granules parathecium: hyaline to slightly brown, with conglutinated, unoriented, short-celled hyphae with narrow lumina, 15-20 µm thick, thinning and disappearing towards surface of the margin epihymenium: interspersed with yellowish brown granules (mostly soluble in K), 15-20 µm thick hymenium: hyaline, (50-)60-80 µm tall; paraphyses: free in water, often branched towards tips, sometimes anastomosing, c. 2 µm thick below; tips: clavate to capitate, 3(-5) µm wide, with yellow-brown apical cells, darker at extreme tip, olive in K; subhymenium: poorly delimited; hypothecium: hyaline, 150-175 µm thick asci: narrowly clavate, 50-60 x 8-10 µm; tips appearing entirely I+ blue [Bacidia-type, ocular chamber mostly indistinct, axial body rather variable] ascospores: hyaline, often few, immature and still in ascus, indistinctly 1-septate, the septum indistinct in water but distinct in cotton blue, mostly oblong-ellipsoid or ob-long-ovoid, sometimes slightly curved, (6-)8-10(-11) x 2-4 µm, thin-walled, usually one oil drop per cell Pycnidia: immersed, c. 130 µm deep and 80 µm wide; ostiole: dark red-brown conidia: filiform, somewhat curved, (10-)1215(-20) µm Spot tests: thallus: K-, C-, P-, UV-; cortex KC-; medulla KC+ red-violet Secondary metabolites: medulla with lobaric acid and an unknown substance (RF 5BC), after charring, both are yellowish gray and UV- (+ bluish gray in B). Substrate and ecology: on rock (granite or unconsolidated rock), in coastal scrub communities; associated with a black-and-white mottled species of Verrucaria (same as in L. lichenicola) World and Sonoran distribution: maritime areas of southern California (north to Monterey Co.) at c. 60 m and Baja California at 20 m. Notes: Lecanora brattiae is a distinctive species, distinguished from most other appressed rosette-forming saxicolous taxa by its weak and spotty thallus pruina restricted to near the lobe tips, initially pruinose brown discs, Bacidia-type asci and narrow, indistinctly 1-septate ascospores, containing lobaric acid with neither usnic acids nor xanthones, and its seashore habitat. It may well belong in a separate, probably undescribed, genus, perhaps together with the rather similar L. alboloba (see under that species for comparisons). It is somewhat similar to L. lichenicola, which occurs in the same habitat (see notes under that species). Although L. brattiae appears similar in many ways to the description and photograph of L. nevegensis Reichert & Galun from Israel, which is described as having a KC+ purplish thallus, the reaction in that species (which is also K+ yellow, C+ purple) is probably not due to lobaric acid, and the medullary hyphae of L. negevensis are only 1-1.5 µm thick.