[Hillebrand's Aspidium hillebrandii (Carruth.) Hillebr. y var.]
Endemic Name honors Edwin Bonsey (1895-1978), American high school physics teacher on Maui and student of Hawaiian ferns. He and his family helped visiting naturalists locate native Hawaiian plants.
Rhizomes short-creeping to decumbent. Fronds up to 100 x 12 cm. Stipes densely covered with narrow, Lanceolate, pale tan to reddish brown scales, larger scales with a dark brown central stripe, scales becoming small, narrow, and hairlike on distal stipes. Blades 2-pinnate, lanceolate, chartaceous, dull; rachises densely clothed with narrow scales and hairlike scales. Pinnae alternate, lowest pinnae as long as or only slightly shorter than middle pinnae, costae and costules densely covered with hairs, hair-like scales, and a few scales. Pinnules and several shallow pinnule lobes tipped with acute spines, margins not cartilaginous, adaxial surface mostly glabrous, abaxial surfaces clothed with long, tan hairs and hairlike scales. Indusia folded, margins becoming irregular, with projecting 1-celled hairs.
Found in upper-elevation mesic and wet forests, and subalpine mesic shrublands, 1,400-2,000 m. common on East Maui and known on Hawai 'i from a single collection from Hualalai.
Polystichum bonseyi may be distinguished from other Polystichum species by fronds not, or only minimally, narrowed at the base and stipes densely covered with pale tan to reddish brown scales, hairlike scales, and hairs, the larger scales with a dark central stripe. Its blade surfaces are not glossy.