Dryopteris hobdyana W. H. Wagner

Endemic

Named for Robert Hobdy, a professional forester with the State of Hawai 'i, who has contributed much to the knowledge of Hawaiian plants.

Plants medium-sized. Rhizomes short-creeping, multibranched, decumbent to erect, branches densely and compactly intertwined, with attached dense mass of last season's dead fronds. Fronds stiffly erect. Stipes stiffly erect, thick, 3-5 mm wide at base; stipe base scales dense, up to 2 x 0.4 mm, overlapping, thin, gray brown, curly. Blades 4-pinnate, 15-85 x 8-35 cm, light green, deltate, appearing sublanceolate due to pinnae ascending and overlapping, appearing folded in a 3-dimensional manner (the fronds are difficult to spread out and press), scales on blades dull green, gray tan, thin, flat; hairlike scales along rachises and costae when young; rachises brown to purplish, shiny. Pinnae up to 20 pairs, lanceolate. Pinnules linear-lanceolate. Ultimate segments oblong to ovate, stalked to broadly adnate, margins with small teeth, herbaceous; minute, glossy, golden glands widely scat-tered along the abaxial segment costae. Veins ending in teeth of ultimate segments. Sori numerous, small. Indusia small.

A recently discovered, locally common fern, 1,800-2,200 m, apparently restricted to the north slope of Haleakala on East Maui and in the northeastern comer of the crater-like summit.

Dryopteris glabra var. hobdyana grows in shrubby, drier, windswept, subalpine clear-ings between the wet forest and grasslands where it is exposed to trade wind-driven weather. Many of this fern's characteristics are probably due to its occurrence in a temperate climate, where it is exposed to much frost throughout the winter months as well as alternating dense moist clouds and clear bright sunlight. In winter it dies back completely, then produces a vigorous, erect spring growth that penetrates the previous year's matted, old fronds.

Plants suggesting a continuum between var. glabra and var. hobdyana have been noted on the north slope of Haleakala and in the Kaupo Gap area of Haleakala. A single rhizome of typical var. hobdyana taken from around 2,150 m on the north slope of Haleakala and transplanted to Lyon Arboretum in Manoa Valley on O'ahu made an abrupt change from producing var. hobdyana fronds to producing fronds typical of var. glabra. Further study may show that this taxon is merely an ecotype.

Dryopteris glabra var. hobdyana may be recognized by its large size; 3-dimensional fronds; usually ascending to upright pin-. nae; massive rhizomes; abundant flattened, deciduous scales along the stipes and ra-. chises; and a dense mat of last season's fronds around the rhizomes.