Common names: pai, palai huna (Hawaiian huna, hidden; palai, fern: the hidden fern)

Endemic

Greek hymen, membrane, + phyllon, leaf, + -oides, resembling, in reference to its thin leaf.

Plants delicate, linear, pendent, epiphytic. Rhizomes short. Fronds clustered, pendulous, 2-20 em long. Stipes often 1/10 frond length or less, less than 0.3 mm diam. including scales. Blades 1-pinnate-pinnatifid to occasionally nearly 2-pinnate, long-linear, small, chartaceous; rachises unwinged. Pinnae 10-40(-75) pairs, not closely spaced, 2-10 mm long, often pinnatifid on acroscopic side of pinnae only, red or amber glands plen-tiful on both surfaces and margins, often deciduous with age. Sori marginal to sub-marginal near tips of lobes, when mature often wider than lobe.

Epiphytic in wet forests, 350-1,750 m, all major islands.

This beautiful and delicate fern is usually found growing in moss on the sides or beneath branches of trees in wet forests; although variable in length, the fronds cari become quite long in favorable environments. It is the most distinctive Adenophorus species, with remarkably uniform morphology. Further DNA and isozyme studies and scanning electron microscopy of the spores may clarify its relationship to the other species in this genus.

Adenophorus hymenophylloides may be recognized by its narrow, linear, pendent, 1-pinnate, clustered fronds with short stalks; short pinnae usually lobed or pinnatifid only on their upper margins; and epiphytic habitat.