Peltula euploca
Powdery rock-olive lichen
This peltate (shield-shaped) lichen grows on acidic rock in arid and desert habitats on every continent! It can often be found in what are known as the "seepage cracks" of inclined, siliceous rocks, and I really hate the word seepage so maybe we can call them like, runoff tracks instead? Wow what a spread! It grows in patches of rounded lobes, each 12-15 cm in diameter, and with down-curled, sorediate margins. The upper surface is olivaceous in color, and the lower surface is paler than the upper surface with a central holdfast attaching it to the substrate. The marginal soredia is granular, and blue-black in color. P. euploca rarely produces apothecia, which grow many-per-lobe, deeply immersed in the thallus surface, and with punctiform openings. It is one of only approximately 10% of lichens that have a cyanobacterial photobiont. Cyanobacterial photobionts tend to prefer moist environments, so I guess we truly have the rock seepage to thank for this glorious little cyano-pal.
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