(Pellaea glabella)
Pellaea glabella-is the-smooth cliffbrake. For much of pteridological history, it was regarded as a reduced form or variety of-Pellaea atropurpurea.-P. glabella-is known to exist in two cryptic species, one-diploid-and one-tetraploid. The diploid reproduces sexually, while the tetraploid is normally-apogamous. It is now known that the tetraploid form of the species is one of the parents of the original hybrid-P. Xatropurpurea-that became the apogamous species.