Rhizoplaca marginalis White rock-posyThis lichen forms thick, monophyllous lobes that look like glob
Rhizoplaca marginalis White rock-posyThis lichen forms thick, monophyllous lobes that look like globs of dried clay or paint. The upper surface is chalky yellow-white or gray-white, and the lower surface is yellowish or grayish brown-black. It is attached to the substrate by a centralized holdfast. It has small, crowded apothecia that grow near the lobe edges. The apothecia have a dark brown-black disc often covered in an obscuring layer of pale pruina. R. marginalis grows on non-calcareous rock overhangs in very limited populations in southern California and Nevada. These limited populations are threatened by the increasing severity of wildfires in the Sierra Nevada regions, and human development. images: source | source | sourceinfo: source | source -- source link