Endemic

Name honors Timothy Ha'alilio (1808-1844), Hawaiian private secretary and business manager for King Kamehameha III in the early nineteenth century.

Plants small, epiphytic. Rhizomes short, erect. Fronds erect to spreading, (2-)3-7(-12) x 0.2-0.5 cm. Stipes short. Blades linear, deeply crenate or with rounded or obliquely triangular lobes, incised 2/3 or less to mid-rib along entire length of blade, distal mar-gins of lobes forming acute angles with midrib, hairs absent or few and scattered. Veins simple to 1-forked on larger blades. Sari usually solitary in lobes on upper 1/4-3/4 of frond, glandular paraphyses present.

Locally common on low mossy branches in wet forests, 600-820 m, Kaua'i (in scattered locations including the Wahiawa Bog area, and North Kaua'i) and O'ahu (on or near the summit ridges of the Ko 'olau Range). Adenophorus haalilioanus is usually found epiphytic on Hedyotis species, but also grows on shrubby 'ohi'a (Metrosideros polymorpha) bushes. This fern appears closely related to A. oahuensis, and forms intermediate to the two species exist. It is not known whether these are hybrids or just extreme variants of each species.

Adenophorus haalilioanus, a small epiphyte limited to Kaua'i and O'ahu, may be easily recognized by its clustered, small, linear fronds with deeply crenate margins.