A unique Hawaiian Schiedea (caryophyllaceae: Alsinoideae) with only five fertile stamens

The floral organogenesis and subsequent ontogenies of the Hawaiian endemic species Schiedea pubescens from Maui, Moloka'i, and Lana'i, and the Wai'anae Mountains, O'ahu, populations previously considered to be varietally distinct, were examined using the scanning electron microscope (SEM). The O'ahu population consistently produced only five fertile stamens, those of the inner whorl. The five stamens of the alternisepalous or outer whorl abort prior to microsporogenesis and fail to elongate. Additional vegetative differences between the two taxa, combined with the floral morphology characters, merit the description of the O'ahu population as a new species, S. pentandra, described herein.