Greek adiantos, unwetted; an ancient name alluding to the water-repellent fronds.

Plants small to medium-sized, terrestrial or epipetric. Rhizomes creeping or erect. Fronds erect to pendent. Stipes round, usually brown to purple or black, shiny, mostly glabrous except at very base, sometimes sparsely hairy or with fibrils. Blades 1-to 8-pinnate. Ultimate segments often rhomboidal, trapezoidal, fan-shaped, or dimidiate, sessile to short-stalked, never adnate. Veins free or rarely anastomosing. Sori marginal along or at vein tips, less than 4 mm wide. Indusial flaps consisting of reflexed margins of pinnae, rectangular or U-shaped.

A genus of about 200 species widely distributed in tropical and temperate areas, mostly at low to mid-elevations and in wet forests. Represented in Hawai'i by one indigenous and three naturalized species, as well as an escaped horticultural cultivar.

KEY TO THE NATIVE AND NATURALIZED ADIANTUM SPECIES IN HAWAI'I

1. Blades repeatedly Y-forked at 4Y angle; stipes and rachises hairy and fibrillose ............................................ 3.A. hispidulum

1. Blades regularly pinnately divided; stipes and rachises glabrous, shiny (2).

2(1). Black color of ultimate segment stalks ending abruptly in a black, saucerlike disk; ultimate segments variable in shape, broadly triangular to diamond-shaped or rhomboidal, stalk attached asymmetrically ........................................ 5. A. tenerum

2. Ultimate segment stalks without black, saucerlike disk, color not ending abruptly at disk; pinnules and ultimate segments fan-shaped, or ovate, obovate to rhomboid, attached centrally at base (3).

3(2). Veins ending at sinuses between marginal teeth; sori U-shaped at bases of sinuses ............................................. 4. A. raddianum

3. Veins ending in marginal teeth (except those ending at sori) or in small sinuses or at rounded margins; sori U-or bar-shaped (4).

4(3). Sori bar-shaped; fronds 15-50 cm long; acroscopic basal pinnules of lower pinnae not overlapping rachises; veins ending in marginal teeth: all major islands and Ni'ihau ............................... LA. capillus-veneris

4. Sori U-shaped; fronds usually larger, up to 100 x 60 cm; acroscopic basal pinnules of pinnae overlapping rachises; veins ending in small marginal sinuses or at rounded margins, not at teeth .................. 2. A. 'Edwinii'