Synonyms: Acrostichum sessile Fee; Elaphoglossum rockii Copel.; E. sessile (Fee) T. Moore Endemic hoe a Maui ("Maui's paddle"), 'ekaha
Latin alatus, winged, in reference to the winged stipes.
Plants medium-sized, terrestrial, occasionally epiphytic. Rhizomes short-creeping, 3-7 cm diam. with scales (4-5 mm without scales), densely covered with soft, narrowly lanceolate, twisted, light to dark brown scales, 10-25 mm long. Stipes winged, wings gradually blending with blades, leaving little or no unwinged stipe. Sterile blades oblanceolate or narrowly elliptic, 35-60 cm long, abruptly or gradually narrowing below, glabrous or with a few scattered scales. Veins parallel, uniting near margin to form a continuous marginal commissural vein.
Common, often growing in large patches in closed-canopy mesic to wet forests, 450-1100 m, only on O'ahu, most common in the Wai 'anae Range, but found scattered in the Ko'olau Range. Elaphoglossum alarum occasionally hybridizes with E. fauriei, the only other species of the Alatum group on O'ahu.
Some names were applied or misapplied to some members of the Alatum group when they were treated in a broad sense and before segregate species were recognized. These include Aconiopteris obtusa Fee, Acrostichum gorgoneum Kaulf., E. gorgoneum (Kaulf.) Brack., and Olfersia obtusa (Fee) T. Moore. Further study and examination of type specimens are necessary to assign these names to the appropriate species.
Elaphoglossum alatum may be recognized by stipes that are winged almost down to the rhizomes; rhizomes with tangled masses of long, brown scales; and parallel veins, free and forking, arising from midrib and all joining to form a continuous vein close to and parallel with the margin. Found only on O'ahu, mostly in the Wai'anae Mountains.