Psilotum (Psilotaceae-Ophioglossales): a taxonomic assessment based on morpho-anatomical studies of the species from the Neotropics

The recent discovery of Psilotum × intermedium in Mexico prompted us to reassess the nomenclature of this genus, which has global implications. From an extensive review of nomenclatural types and herbarium specimens, field collections, and a morpho-anatomical analysis, P. nudum and P. flaccidum are treated as accepted species, while P. × complanatum is treated as an interspecific hybrid between them. With this clarification, we specify their main synonymies and designate seven lectotypes (for Bernhardia schiedeana , Psilotum complanatum var. latissimum , P. complanatum var . mexicanum , P. floridanum , P. neocaledonicum , P. triquetrum , P. triquetrum var. gracile ) and we select an epitype to give taxonomic support to the hybrid. We provide descriptions, diagnostic comments, and a key for identification of the accepted taxa, and also update the geographical ranges of these three taxa, mainly in Neotropics.