This is restricted to recessed walls of non-calcareous cliffs, mostly in Appalachian regions. It is known only from its thalloid gametophytes, and was known informally as the "Appalachian Gametophye" until described by Farrar & Mickel (1991); see W for review. The only known plants west of Appalachian regions are along sandstone cliffs of the Shawnee Hills in Ky.