Synonym: Dryopteris palikuensis Fraser-Jenk.

Endemic

Latin sub, almost, approaching, + bi-, two, +pinnate, winged, feathered, alluding to the nearly 2-pinnate character of the frond.

Plants medium-sized to large, terrestrial. Rhizomes decumbent to erect, covered with dense masses of linear, orange brown to chestnut brown scales with dark centers. Fronds in a shuttlecock arrangement on apexes of erect rhizomes, up to 2 m long.

Stipes densely covered with scales similar to those on rhizomes. Blades mostly 1-pinnate-pinnatisect, but ranging from 1-pinnate-pinnatisect to 2-pinnate-pinnatifid, dark green adaxially, light green abaxially, coria-ceous, adaxial surfaces appearing somewhat rough, pinnae shorter at bases; rachises densely covered with narrow scales like those on upper stipes. Pinnae 20-28 pairs, usually overlapping in middle and lower parts of blades, middle pinnae 10.5-12 x 3.2-4.5 cm, lower pinnae same size or only slightly smaller than middle pinnae, costae grooved, pinnae toward middles of blades tending to droop downward from their middles to their tips (more apparent in living plants). Ultimate segments 10-25 x 5-10 mm, crenate to lobed, bases often con-stricted or stalked in lower parts of blades, tips rounded, dentate, costae and veins with small scales. Veins pinnate, free, 1-to 7-forked. Sori round, submedial, mostly 4-7 pairs per segment, found mostly on distalll 2 of frond. Indusia reniform.

Common in scattered spots in wet and shady or open areas, 1,650-2,200 m, on the north slopes of HaleakaHi on East Maui, Pu'u Kukui on West Maui, and scattered on Hawai 'i Island. Usually associated with Dryopteris wallichiana.

This variable species often resembles D. wallichiana when growing in more exposed areas, but at wet, shady forest edges it has a very different, more foliose appearance, and its characters are more completely developed. This species may be an apogamously (asexually) reproducing hybrid between D. wallichiana and an unknown 3-to 4-pinnate Dryopteris. Morphologic, spore, and chromosome studies, as well as DNA and isozyme investigations, could clarify its origins.

Dryopteris subbipinnata is found on the north slopes of Haleakala and at Palikil in the "crater,' the summit of West Maui, and scattered on Hawai'i Island. It can resemble D. wallichiana, but is easily dis-tinguished by its usually larger size, over-lapping pinnae, lowermost pinnae that are only slightly smaller or the same size as those above, greater blade dissection, and crenate to lobed ultimate segments. In live plants the pinnae in the middle part of the frond tend to droop downward, a condition not seen in D. wallichiana.