Worldwide in wet tropics and subtropics, a few in temperate latitudes.
Species outside the flora display a wide range of morphologies and habits, and many are somewhat larger than North American species.
Some authors divide the Hymenophyllaceae into 30 or more genera. The subdivisions of these genera are treated here as subgenera and sections, following C. V. Morton (1968).
Although plants of the Hymenophyllaceae clearly have the capacity to withstand periodic desiccation and freezing, they have a delicate nature that requires they grow in deeply sheltered habitats of nearly continuous high moisture and humidity. This undoubtedly accounts for the relative rarity of all species in the flora. Possibly they are currently restricted from more widespread pre-Pleistocene occurrences. All owe their continuing existence largely or entirely to vegetative propagation by either the sporophyte or gametophyte generation. The capacity for vegetative reproduction and dispersal by gametophytes of the Hymenophyllaceae allows gametophyte colonies to persist indefinitely without completing a life cycle. In the flora, several species are maintained exclusively as gametophytes with sporophytes rarely or never produced.
Genera 6, species ca. 650 (2 genera, 11 species in the flora).
|1||Soral involucres 2-valved, the halves roundish to ovate, sporangial receptacle enclosed within involucre; gametophytes entirely ribbonlike, branched; gemmae platelike or absent.||Hymenophyllum|
|1||Soral involucres conic, sporangial receptacle (bristle) becoming exserted beyond involucre; gametophytes entirely filamentous or proximally filamentous with aerial blades; gemmae uniseriate.||Trichomanes|