Endemic

Latin erectus, upright.

Plants medium-sized, terrestrial or epipetric. Rhizomes short-creeping to upright. Fronds 20-70 x 5-12 cm. Stipes black to purplish black, shiny, scales at bases sparse, 2-5 mm long, clathrate, brownish or black. Blades 1-pinnate, with forms rarely up to 3-pinnate, lanceolate to linear-lanceolate; rachises black, shiny. Pinnae 15-50 pairs, middle pinnae 0.5-6 X 0.2-1.5 cm, green to gray green, basal pinnae often smaller, margins usually entire, sometimes undulate, laciniate, or deeply lobed to again 2-pinnate (in f. alexandri). Pinnules and ultimate segments wedge-shaped if present (in f. alexandri). Veins variable, usually free, sometimes more or less joining at margins in support of sori, areoles near base of pinnae uncommon (usually found only on plants from Molo-ka'i and Maui). Sari marginal to submarginal, sometimes on short marginal projections, opening outward, single sori borne on vein tips, or coenosori borne on 2 or more vein tips joining to form a marginal commissure.

Very rare federally listed endangered species, usually occurring on cinder rocks or loamy soil in dry to mesic forests, 500-1,700 m, historically documented from all the major islands but now known only from a few scattered, small, isolated populations.

Diellia erecta is the most variable and historically the most widely distributed species of Diellia, although it is now among the rarest. It occurred on loamy slopes, boulders, and rocky soils in mesic forests on all major islands, but is now known from two sites in the southern Ko'olau Range of O'ahu, several on Moloka 'i, a few on Maui, and one each in Manuka and Honomalino on Hawai 'i. It is probably extinct on Kaua'i and Lana'i.

Diellia erecta, the only Diellia known historically from all the major islands, may be recognized by its black, shiny stipes and rachises, and veins free to occasionally joining under the sori along the pinna margins, only uncommonly forming areoles at the pinnae bases. Pinna forms range from entire to undulate, deeply lobed, or to 2-to 3-pinnate.