Common names: palai la'au

Endemic        

Name derivation obscure.

Plants epiphytic. Rhizomes clustered, usu-ally decumbent. Stipes round to slightly winged, soon blending into blade. Fronds 1 0-40+ x 1.3-2.2+ em. Blades pendulous, linear, deeply pinnatifid, cut nearly to costae, uniform in width, hairs plentiful, with 3-8 cells, marginal, glands absent; lobes oblong to narrow, 5-15 mm long, distal margins of lobes nearly perpendicular to mid-rib (when alive the lobes curl away from plane of blade). Veins pinnate with several branches. Sori in two rows with abundant glandular paraphyses.

Epiphytic in wet forests, about 700-1,300 m; historically known from all the major islands, but now limited to small populations on Kaua'i and Moloka'i, and a larger popu-lation in the Glenwood area on Hawai 'i Island. It is most commonly found on 'ohi'a (Metrosideros polymorpha) trees.

Adenophous periens is a federally listed endangered species. It was formerly not an uncommon epiphyte and the cause of its cur-rent rarity is unknown. The most distinctive member of the subgenus Oligadenus, it is not closely related to the other species, and further study is needed to clarify its status.

Adenophorus periens, a long, narrow, linear, uniformly wide fern, may be easily distinguished from A. pinnatifulus by its hairy blade margins, upper lobe margins perpendicular to the midrib, and lobes on living plants that rotate like louvers out of the plane of the pendent fronds, giving it a "venetian-blindlike" quality (lobes all in one plane on A. pinnatifidus).