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.[1] It is commonly called button jelly lichen or bat's wing lichen.[1] It is blackish-green when wet, and dark brownish-green to dark olive when dry.[1] The photosynthetic partner is the Nostoc cyanobacterium that is spread throughout the thallus (main body part).[1] 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.[1] It has dark purple-brown apothecia all over.[1] It produces no reaction to lichen spot tests.[1]