Rinodina laevigata (Ach.) Malme

Location: Madison Heights, Pasadena, Los Angeles Co., California, USA

Notes: crustose lichen, on bark of ash, in spray zone of sprinklers
THALLUS: light to medium gray-green, scabrid, dull, K-
APOTHECIA: lecanorine; disk black, matte, epruinose, flat to convex; rim gray-green like thallus, crenulate, barely raised, persistant, filled with algae, cortex thin and uniform; epihymenium brown due to paraphyses tips; hymenium clear; hypothecium clear; paraphyses simple, abruptly clavate, with brown caps
SPORES: clear then gray then dark brown, elliptical, smooth, 2 cells, 8 per ascus, uneven walls (apical thickening and angular septum when young, lumina inflating in age, sometimes forcing apical thickening to protrude as a snout, torus present and rarely swelling slightly in K), large round oil bubble usually present inside mature lunina, sometimes curved when young, 14-15 × 7-8 µm
Spore structure at various stages of development is critical for this genus, and difficult to learn. I’m pretty confident I’ve diagnosed this one correctly, though. This is a cosmopolitan species — which you would expect of a “lawn weed” like this.

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