The Pteridophyte Phylogeny Group classification of 2016 (PPG I) suggests that the genus contains about 10 species.[1] As of February 2020[update], the Checklist of Ferns and Lycophytes of the World noted that the species circumscription was "fairly controversial and fluctuating", and accepted 34 species and hybrids:[3]
^ abcdPPG I (2016). "A community-derived classification for extant lycophytes and ferns". Journal of Systematics and Evolution. 54 (6): 563–603. doi:10.1111/jse.12229. S2CID39980610.
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