Collema nigrescens
in Northwestern California
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Ascomycota
Class:	Lecanoromycetes
Order:	Peltigerales
Family:	Collemataceae
Genus:	Collema
Species:	C. nigrescens
Binomial name
Collema nigrescens (Huds.) DC. (1805)
Synonyms
Lichen nigrescens Huds. (1762)

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]: 34, 36} It is commonly called button jelly lichen or bat's wing lichen.^{[1]: 34, 36} It is blackish-green when wet, and dark brownish-green to dark olive when dry.^{[1]: 34, 36} The photosynthetic partner is the Nostoc cyanobacterium that is spread throughout the thallus (main body part).^{[1]: 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.^{[1]: 34, 36} It has dark purple-brown apothecia all over.^{[1]: 34, 36} It produces no reaction to lichen spot tests.^{[1]: 34, 36}