Graphis
Crustose lichens containing a trentepohlioid alga; thallus smooth, cracked, scurfy, somewhat granular or, in some species, areolate; apothecia lirellate, often asterisk-like or snaking, with paired, thick lip-like rims that truncate or attenuate to points, these generally partly or completely covered over in extensions of the thallus; disc usually slit-like, sometimes gaping, white-pruinose in some species; exciple formed of hyphae that are usually obscured in brittle masses of dark brown pigment; hymenium formed of very straight, usually unbranched hyphae, often with pale brown pigments in the walls at the tip; hypothecium generally thin and colourless; asci thin-walled but with a slight apical thickening with a shallow ocular chamber, IKI-; spores 1-8 per ascus, colourless or rarely brownish with overmaturity, I+ purple in the walls, elliptic to elliptic-fusiform, the septae thickened toward their connections to the outer wall such that the lumina are elliptical, some species with both longitudinal and transverse septae.
References: Staiger & Kalb 2004.
Graphis scripta (L.) Ach.
Thallus white, pale greyish green, or creamy whitish, smooth or verruculose; apothecia jet black, snaking and often branching, the branches 1-3 × 0.2-0.6 mm, the rim lip-like, with or without thalline tissues ascending up the sides; hymenium 90-100 µ high; spores 25-45 × 7-9 µ, with 7-10 septae.
Reactions: K+ brownish yellow, C-, KC-, PD-.
Contents: No known lichen substances.
Habitat: On smooth bark of conifers in humid forests, especially along lake and river shores, less often on smooth parts of thick bark plates on old trunks. Rarely on bark of broadleaf trees and shrubs. Lower elevations.
Similar Species: Opegrapha herbarum has consistently shorter apothecia and spores with thin walls and blocky lumina. Arthonia dispersa may appear very similar, but lacks the well-developed rim, and has thin-walled spores with only a single septum. Arthonia excipienda has short apothecia and a thin, less conspicuous rim, and has thin-walled spores with a single septum.
Specimens: Björk 13956; Goward 96-853, 02-15.
Local Status: Rare.
Notes: The thallus of G. scripta is described as K-, but I have consistently observed a K+ brownish yellow reaction.