A reduced circumscription of Balaustion and description of the new genus Cheyniana (Myrtaceae: Chamelaucieae)
RYE, B.L.

The myrtaceous genus Balaustion Hook. is reduced to its original monotypic circumscription. Balaustion s. str. is closely related to Tilophloia Trudgen & Rye ms., both genera having stamens in a single circular series, broad filaments, a very large placenta and seeds with a large concave hilum, but Balaustion is distinguished by its prostrate habit with adventitious roots, basifixed anthers and long tubular flowers adapted to pollination by birds. A second bird-pollinated species with elongated flowers, previously known as B. microphyllum C.A.Gardner, is transferred into the new genus Cheyniana Rye as C. microphylla (C.A.Gardner)  Rye. Since the type material of this species is missing, it is lectotypified on the original illustration. Another large-flowered species, but with more spreading, apparently insect-pollinated flowers, is described as C. rhodella Rye & Trudgen. Cheyniana is related to also Oxymyrrhine Schauer, which it resembles in its very reduced anthers and narrow filaments, but differs in its large colourful petals and woody indehiscent fruit. Both of the small genera treated in this taxonomic revision belong to the tribe Chamelaucieae and are restricted to the south-west of Western Australia.