Wood anatomy and relationships of Neowawraea (Euphorbiaceae)

Wood anatomy of three specimens of Neowawraea phyllanthoides Rock, a rare and endangered member of Euphorbiaceae endemic to the Hawaiian Islands, is described and compared with woods of other genera of subfamily Phyllanthoideae. Neowawraea has often been associated or synonymized with Drypetes Vahl. Wood of Neowawraea is diffuse porous, perforation plates are simple, imperforate tracheary elements are thin-walled septate fiber-tracheids, rays are heterocellular and crystaliferous, and axial xylem parenchyma is restricted to a few scanty paratracheal and terminal cells. In several respects these results differ from earlier published descriptions of the wood of this taxon; these earlier descriptions are shown to be in error. Further, as described here, wood of Neowawraea differs greatly from that of Drypetes. Accordingly, generic status for Neowawraea is warranted on anatomical grounds and relationship with certain genera of tribe Phyllantheae such as Breynia Forst., Glochidion Forst., or Phyllanthus L. is favored over relationship with Drypetes. Neowawraea Rock is a monotypic genus of dioecious trees endemic to the Hawaiian Islands. Historically recorded from Kauai, Oahu, Molokai, Maui, and Hawaii (St. John 1973), the species is currently considered in danger of extinction (Fosberg & Herbst 1975). Given its scarcity, and the fact that female flowers have never been described (St. John 1973), it is not surprising that proper understanding of its relationships has yet to be achieved. Neowawraea phyllanthoides was discovered by Joseph Rock (1913) on rough aa lava flows of Mauna Loa. Rock described this new genus and species on the basis of male flowers and mature fruits, the only material known at that time.