This is a fern, P. atropurpurea, commonly known as purple-stem cliffbrake or just purple cliffbrake. Brake is an old word for fern, related to the word bracken. Like many other members of the Pteridaceae, it is a rock plant, needing a calcareous substrate.
P. atropurpurea is an apogamous autotriploid, with 3n=87 (actual base number, n=29), and is one of the historical parents of the hybrid species complex, Pellaea glabella. Apogamy, or the ability to reproduce non-sexually, is common among rock ferns in the Pteridaceae.
This fern produces clumps of widely arching fronds. The stipe and rachis of the blade are purple, while the blade itself has a blue-gray tinge to it. The upper pinnae are long, narrow, and undivided, while the lower ones are divided into 3-15 pinnules. The pinnae are, for the most part, opposite. Fertile fronds are longer and more heavily divided. They produce sori, which lack a true indusium, within the inrolled margins of the pinnae.
This plant may be distinguished from the similar Pellaea glabella by its hairier nature and larger form.
- Catling, P.M. and Brownell, V.R. 1999. Alvars of the Great Lakes Region. p. 375-391, in R. C. Anderson, J. S. Fralish, and J. M. Baskin (eds.) Savannas, Barrens and Rock Outcrop Communities of North America. Cambridge: Cambridge University Press. Table 23.3
- Boughton C. 2005. Ferns of Northeastern and Central North America. New York: Houghton Mifflin. 417p.
- USDA Plants Database: P. atropurpurea
- P. atropurpurea in Flora of North America
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