About Collema nigrescens (Huds.) DC.
Collema nigrescens is a foliose (leafy) jelly lichen belonging to the genus Collema. It is commonly known as either button jelly lichen or bat's wing lichen. This lichen grows on the bark of trees, such as bigleaf maples, in wetter coastal regions of California. When wet, it appears blackish-green; when dry, its color ranges from dark brownish-green to dark olive. Its photosynthetic partner is the cyanobacterium Nostoc, which is distributed throughout the thallus, the main body of the lichen. Even though it has a foliose growth form, like all jelly lichens, its thallus is undifferentiated. It lacks distinct layers, as well as an upper or lower cortex, and its cyanobacterial partner is spread evenly through the entire thallus. Dark purple-brown apothecia are found all over the lichen's surface. Collema nigrescens shows no reaction to standard lichen spot tests.
