Pilophorus acicularis, commonly known as the nail lichen or the devil's matchstick, is a species of lichen in the family Cladoniaceae. It was originally described in 1803, and transferred to the genus Pilophorus in 1857. A fructicose (shrub-like) species, it grows directly on silicate rocks in dense clusters. The lichen starts out as a granular crust on the rock surface, and develops stalks, or pseudopodetia, up to 3 cm (1.2 in) tall and about 1 mm thick that have rounded black apothecia at the tips. The stalks are erect and curved so as to appeared combed. It is found on the west coast of North America up to Alaska, and in eastern Eurasia. In addition to green algae, the lichen contains cyanobacteria that help contribute to soil fertility by supplying fixed nitrogen.