Cystopteris fragilis (Linnaeus) Bernhardi. Fragile Fern, Brittle Fern. Phen: Jun-Sep. Hab: Cliffs, ascending in our area to 1650 m. Dist: Circumboreal, in North America ranging from NL (Newfoundland) west to AK, south to MA, CT, NJ, montane NC, VA, w. OK, NM, and AZ; Central America.

Origin/Endemic status: Native

Other Comments: This "species" has been interpreted to be a fertile allotetraploid, presumed to be derived from hybridization between C. reevesiana Lellinger and an extinct or currently undiscovered second parent (C. "hemifragilis"), with a genome symbolized HHRR (Paler & Barrington 1995). However, Rothfels et al. (2014) demonstrated that "C. fragilis" appears to be an allopolyploid complex of many diploid, tetraploid, and hexaploid entities needing further study and taxonomic recognition (also see FNA for discussion).

Synonymy: = FNA2, FoC, Il, K1, K3, K4, Meso1, NE, NY, Pa, W, Shmakov, Batkin, & Vaganov (2018); = Cystopteris fragilis (L.) Bernh. var. fragilis – C, F, G, GrPl, Sf; = n/a – RAB; < Cystopteris fragilis (L.) Bernh. – WV; < Filix fragilis (L.) Underw. – S13

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