Abstract
Petrosavia amamiensis (Petrosaviaceae) is described as a new species from Amami-Oshima Island, Kagoshima Prefecture, Japan. The plants were previously identified as P. sakuraii. The flowers of P. amamiensis are autonomously self-pollinated at the beginning of anthesis, while those of P. sakuraii are self-pollinating at a later stage of anthesis. Petrosavia amamiensis has a shorter aerial stem, shorter internodes, more densely flowered inflorescence and smaller seeds than P. sakuraii. Moreover plastid and nuclear DNA differ greatly between P. amamiensis and P. sakuraii.
