Adiantum raddianum Presl [syn. A. cuneatum Langsdorff & Fischer], Delta Maidenhair, is now the most common species of Adiantum in the Islands, where it grows on moist and shaded rocks, slopes, and river and roadside banks. Wagner cited a collection by Abbé Faurie from Kealia, Kaua'i, made in January 1910, as the first wild-collected record. He also quoted from a 1949 letter by H. L. Lyon, who wrote that he had first seen A. raddianum in the wild in 1907 and that by 1949 it had become widespread. A form with small, narrow segments and brown indusia grows on the slopes of Haleakala from 900 to 2400 m (Hobdy 3482 & 3484, BISH). This alien species continues to spread, whereas the indigenous A. capillus-veneris L. is now uncommon and is apparently being replaced by A. raddianum.
