Acarospora
Crust lichens having a trebouxioid alga in lobed, areolate or inconspicuous thalli of a brown, grey, green or yellow colour; apothecia sunken in the thallus, the margin usually formed by the thallus itself, usually lacking any noticeable exciple; hymenium formed of mostly simple, straight paraphyses embedded in gel, often with pigments around their apices; asci with a distinct tholus, IKI- or IKI+ blue in some species; spores numerous per ascus (mostly more than 100), small, elliptic or oblong, lacking septae.
References: Clauzade & Roux 1985.
| 1a. | Areoles in dense patches, the outermost ones weakly lobate; apothecia rising up from the areoles, with a distinct rim darker than the thallus …Acarospora similis |
| 1b. | Areoles solitary or a few clustered together, never lobate; apothecia remaining sunken within the areoles, lacking a rim …Acarospora veronensis |
Acarospora similis H. Magn.
Thallus of large, irregularly polygonal, medium to dark brown areoles 0.2-1.4, somewhat glossy; apothecia partly sunken in the areoles, especially when young, but later partly emerging with a thin, dark rim and sometimes also a distinct thalline rim, the disc sometimes with an umbo (nipple-like apiculus in the centre); hymenium orange-brown in upper portions; paraphyses 2-3 µ wide; spores narrowly elliptical 3-6.5 × 1-1.5 µ.
Reactions: All spot tests negative.
Contents: No lichen substances known.
Habitat: Seen only once: on bark of a large Pseudotsuga root in a dry, middle elevation forest.
Similar Species: Unlikely to be confused with any local epiphytic crust.
Specimens: Björk 17838.
Local Status: Rare.
Acarospora veronensis A. Massal.
Thallus of somewhat glossy, dark brown areoles, these solitary or few together arrayed haphazardly in clusters, not in rosettes, prothallus absent or very inconspicuous; apothecia a dimple-like depression in the areole center, usually 2-3 per areole, darker brown than the thallus, with a thin non-algal rim evident only in cross-section; spores 3-5 × 1.5 µ.
Reactions: All spot tests negative.
Contents: No lichen substances known.
Habitat: Usually on rock, but sometimes also on worked wood. In our area observed on painted wood of a picnic table.
Similar Species: No similar epiphytic species, but other species of Acarospora may eventually be found on worked wood.
Specimens: Björk 11645.
Local Status: Rare.