Collema nigrescens

Collema nigrescens is a leafy (foliose) jelly lichen (Collema genus) found growing on the bark of trees such as bigleaf maples, in wetter coastal parts of California.^: 34, 36 It is commonly called button jelly lichen or bat's wing lichen.^: 34, 36 It is blackish-green when wet, and dark brownish-green to dark olive when dry.^: 34, 36 The photosynthetic partner is the Nostoc cyanobacterium that is spread throughout the thallus (main body part).^: 34, 36 Although foliose in form, like all jelly lichens, the thallus is not differentiated, lacking layers or an upper or lower cortex (lichen) and the cyanobacteria is spread throughout the thallus.^: 34, 36 It has dark purple-brown apothecia all over.^: 34, 36 It produces no reaction to lichen spot tests.^: 34, 36