Clarification of two poorly known vittarioid ferns (Pteridaceae): Haplopteris angustissima and H. capillaris

Two poorly known Malesian vittarioid ferns, Haplopteris angustissima and Monogramma capillaris are noteworthy for their similar gross morphology. In this study, their systematic relationship was clarified by using molecular phylogenetic analysis which resolved the species in two different clades. Diagnostic morphological characters were further revealed by detailed comparison of almost all the known collections. Although overlaps were found in most of the investigated morphological characters, the venation and silica bodies were found to be useful for species delimitation. Type information, field images, illustrations, and taxonomic notes are provided for both species. A new combination Haplopteris capillaris is made and its occurrence in Taiwan as independent gametophytes is confirmed.