Synonym(s): Adiantum cuneatum Langsd. & Fisch.

Naturalized

Name honors Giuseppe Raddi (1770-1829), an Italian botanist.

Plants delicate, terrestrial or epipetric on moist, rocky banks. Rhizomes short-creeping. Fronds erect-arching, close, 15-45 cm long. Stipes dark reddish brown to black, shiny, glabrous except scaly at base. Blades 2-to 4-pinnate, broadly to narrowly deltate. Pinnae linear-deltate, fan-shaped if not again divided. Ultimate segments fan-shaped with centrally attached stalk, membranous, outer margins rounded, toothed, often lobed or cleft. Veins ending at sinuses between marginal teeth. Sori often 1-2 per segment, U-shaped at bases of sinuses.

Common on moist consolidated cinder, and basalt banks along trails and streams, sea level to 4,400 m, all major islands. Native to the American Tropics, Adiantum raddianum was first collected in the wild on Kaua 'i in 1910, but was reportedly seen outside of cultivation as early as 1907.

Adiantum raddianum is the most com-mon Adiantum species in Hawai'i and the species commonly seen on moist banks along trails. Its U-shaped sori easily distinguish A. raddianum from the native A. capillus-veneris, which has bar-shaped sori.