E. North America: present S.E. Asia: present north temperate regions and south to Himalayas: present
Three species, one widely distributed in north temperate regions and south to Himalayas, one in E. North America, one in S.E. Asia.
Base chromosome number 30: P. connectilis triploid; P. hexagonoptera diploid; P. decursive- pinnata diploid and tetraploid.
Fee and other authors of the 19th Century included in this genus free-veined species resembling Nephrodium but lacking indusia; Mettenius admitted also species with anastomosing veins. The result in either case was an unnatural mixture. Ching was the first author to restrict the genus in the sense here accepted. The species described below differs from the type in elongate fronds on a suberect caudex.