Pellaea glabella

Smooth cliffbrake
Conservation status
Secure  (NatureServe)
Scientific classification
Kingdom:	Plantae
Division:	Pteridophyta
Class:	Polypodiopsida
Order:	Polypodiales
Family:	Pteridaceae
Genus:	Pellaea
Species:	P. glabella
Binomial name
Pellaea glabella Mett. ex Kuhn
Synonyms
Pellaea atropurpurea (L.) Link var. glabella (Mett. ex Kuhn) F.C. Gates Pellaea atropurpurea (L.) Link var. bushii Mack.

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.

P. glabella is epipetric, normally growing on well-weathered limestone. It favors more exposed sites than P. atropurpurea.

This species is distinguished by its sessile or nearly sessile pinnae and smooth, not hairy, stipes.

P. glabella has been assigned a total of four subspecies:

• Pellaea glabella subsp. glabella Mettenius ex Kuhn
• Pellaea glabella subsp. missouriensis (G. J. Gastony) Windham
• Pellaea glabella subsp. occidentalis (E. E. Nelson) Windham
• Pellaea glabella subsp. simplex (Butters) A. Löve & D. Löve

The subspecies glabella and simplex are the tetraploids, while missouriensis and occidentalis are the diploids. Glabella and missouriensis have hairlike scales near the midrib, while simplex and occidentalis are completely glabrous.

References

• P. glabella USDA Plants Profile: http://plants.usda.gov/java/profile?symbol=PEGL
• P. glabella in Flora of North America: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500875