Hymenophyllum dichotomum

This species have been treated in Trichomanes, Microtrichomanes, and Hymenophyllum subg. Sphaerocionium. Ebihara et al. (2004) considered this species to be an elongate form of H. digitatum sensu lato.   Considering their discussion of the problem, I prefer to maintain this taxon as distinct until further research has been done. They report “All taxa possessing marginal setae are herein tentatively placed in H. digitatum. Typical forms of T. dichotomum and T. taeniatum are easily recognizable; however, intermediate forms between H. digitatum and these are often found. Braithwaite (1975) pointed out that leaf sizes were related to their ploidy; i.e., the tetraploid (n = c.72) has larger fronds than the diploid (n = 36). Our molecular data also suggest there is much genetic diversity within this complex, though their monophyly has been supported thus far.”

Ebihara, Atsushi, et al. “Polyphyletic origin of Microtrichomanes (Prantl) Cope.(Hymenophyllaceae), with a revision of the species.” Taxon (2004): 935-948.