Resurrection of Genus Kadua for Hawaiian Hedyotidinae (Rubiaceae), with Emphasis on Seed and Fruit Characters and Notes on South Pacific Species

We examined shapes and surface features of seeds of 19 species of Hawaiian Hedyotideae using scanning electron microscopy. The study concentrates on the Hedyotideae previously recognized in the genus Hedyotis and here recognized as the genus Kadua, lacking diplophragmous capsules, and having salverform, fleshy corollas with appendaged lobes. The seeds fell into four main morphological groups: (1) hat- or fan-shaped, laterally cuneate, compressed seeds (Kadua subg. Kadua and atypical species of Gouldiopsis and Wiegmannia); (2) ovoid or elliptic seeds with conspicuous bubble-shaped bodies included in the areoles (cells) (most of sect. Wiegmannia); (3) flat broadly winged seeds with a lateral hilum attached at wing margin (Kadua centranthoides, type species of sect. Gouldiopsis); (4) brick-like or blocky seeds with a centric ventral hilum (Kadua subg. Gouldia). The results of the seed study correlate with the taxonomic arrangement in the current Hawaiian flora. An appendix lists the Kadua names including necessary new combinations and their Hedyotis synonyms for the Hawaiian taxa and seven additional South Pacific taxa having the same corolla characters. The following new names are published: Kadua subg. Gouldia (A. Gray) W. L. Wagner & Lorence, Kadua sect. Gouldia (A. Gray) W. L. Wagner & Lorence, Kadua fosbergii (W. L. Wagner & a R. Herbst) W. L. Wagner & Lorence, Kadua axillaris (Wawra) W L. Wagner & Lorence, Kadua sect. Phyllozygia (W. L. Wagner & Herbst) W. L. Wagner & Lorence, Kadua tryblium (D. R. Herbst & W. L. Wagner) W. L. Wagner & Lorence, Kadua sect. Oceanica (Fasberg) W. L. Wagner & Lorence, Kadua sect. Austrogouldia (Fosberg) W. L. Wagner & Lorence, Kadua lucei (Lorence & J. Florence) W. L. Wagner & Lorence, Kadua nukuhivensis (J. Florence & Lorence) W L. Wagner & Lorence, Kadua tahuatensis (Lorence & J. Florence) W. L. Wagner & Lorence, Kadua grantii (Fosberg) W. L. Wagner & Lorence, Kadua sect. Protokadua (Fosberg) W L. Wagner & Lorence, Kadua coriacea (J. E. Smith) W. L. Wagner & Lorence, Kadua sect. Gouldiopsis (Fosberg) W. L. Wagner & Lorence, Kadua foggiaria (Fosberg) W L. Wagner & Lorence, Kadua sect. Wiegmannia (Meyen) W. L. Wagner & Lorence, Kadua cordata Cham & Schltdl. subsp. remyi (Hillebr.) W L. Wagner & Lorence, Kadua cordata Cham & Schltdl. subsp. waimeae (Wawra) W. L. Wagner & Lorence, Kadua degeneri (Fosberg) W. L. Wagner & Lorence, Kadua degeneri (Fosberg) W L. Wagner & Lorence subsp. coprosmifolia (Fosberg) W. L. Wagner & Lorence, Kadua elatior (H. Mann) W. L. Wagner & Lorence, Kadua flynnii (W. L. Wagner & Lorence) W. L. Wagner & Lorence, and Kadua st-johnii (B. C. Stone & Lane) W. L. Wagner & Lorence.