Sirochloa, a New Bamboo Genus from Madagascar (Poaceae-Bambusoideae)

Abstract

Summary. Sirochloa, a new genus from Madagascar, is described, with one species S. parvifolia (Munro) S. Dransf., transferred from Schizostachyum Nees. It is characterised by the determinate inflorescence with the presence of subtending bracts and prophylls. The lemma possesses a long awn, and the branch system is unusual in having secondary branches developed most probably independently from the dominant main branch. The genus appears morphologically most similar to Decaryochloa A. Camus, a monotypic genus endemic to Madagascar. There is a beautiful slender bamboo that occurs in great abundance in forest on white sand along the east coast of Madagascar. It often forms curtains of foliage hanging from forest trees. This distinctive bamboo has long been known as Schizostachyum parvifolium Munro, which together with S. bosseri A. Camus, represent the only members of the genus in Madagascar. However, some of the supposed members of Asiatic bamboo genera (e.g. Cephalostachyum, Ochlandra, Schizostachyum) recorded as endemic to Madagascar, have been shown to be generically distinct (Dransfield 1998), and the subject of this paper is no exception. Schizostachyum parvifolium was described by Munro in 1868 from Madagascar and Mayotte (Comoro Islands). Munro (1868) cited three specimens: Boivin 1978 (sterile, two sheets at K) from Nosy-Be in Madagascar, Gerrard 74 (with inflorescences) from Madagascar (without locality), and Boivin 3030 (with inflorescences) from Mayotte. Of these, one sheet of Boivin 1978, Gerrard 74 and Boivin 3030 all appear to represent the same taxon. In these specimens, the sheath scar is horizontal, and branches are borne above this horizontal sheath scar. The second sheet of Boivin 1978 differs in having the sheath scar dipping downwards where the branches are borne, and is not S. parvifolium. It belongs to a different genus, most probably Valiha S. Dransf. Throughout his monograph Munro (1868) did not mention type species or type specimens in describing new genera and new species. In the case of Schizostachyum parvifolium, I here designate Gerrard 74 as the lectotype of this species, because this specimen consists of a piece of the main culm, which is solid, and a node with several leafy branches each terminated by a flowering branch. No locality of Gerrard 74 is cited, but Dorr (1997) states that Gerrard collected only from the east coast near Toamasina (Tamatave). Other specimens lack parts of the main culm. Bentham (in Bentham & Hooker 1883) noted that the placement of this taxon in Schizostachyum is doubtful, for it resembles Nastus Juss. rather than