The Austral-Pacific Species of Decaspermum (Myrtaceae)

Abstract

Decaspermum was described by Forster (1776) consisting of a single species, D. fruticosum, collected in the Society Islands. It was distinguished from Myrtus by the several-locular ovary, each locule usually with a pair of ovules, and the seeds separated in the fruit by a vertical false septum in the middle of each locule. Gaertner (1789) described Nelitris with one species, N. jambosella, from Ceylon, including Decaspermumfruticosum as a synonym but based on a specimen now known as Timonius jambosella Thwaites (Rubiaceae) (see Trimen, 1894). Nelitris appears to be an illegitimate name because D. fruticosum was included as a synonym of N. jambosella.* The name Nelitris was subsequently taken up instead of Forster's Decaspermum and 23 names have been published in Nelitris. The priority of Decaspermum was recognized by Kurz (1877). The species limits in Decaspermum have generally been confused and one species is usually considered to be widespread throughout Malesia and Southeast Asia to southern China (Merrill & Perry, 1938). This species was recognized as D. paniculatum (Lindl.) Kurz by Kurz (1877), Duthie (1878) and Niedenzu (1893). However, Merrill (1917, 1923) considered that the Malesian species was conspecific with D. fruticosum and this name has been used by Amshoff (1944) and Merrill & Perry (1938). Comparison of D. fruticosum from the type locality in the Society Islands with the Malesian collections named as D. fruticosum or D. paniculatum shows that they differ in a number of important characteristics. In D.fruticosum the flowers are mostly solitary and axillary with large bracteoles, while in Malesian collections the flowers are in thyrses or racemes and are often paniculate with small deciduous bracteoles. The Malesian collections appear to belong to a variable species which may be called D. parviflorum (Lam.) A. J. Scott (see sp. 9, p. 66), although more than one taxon is probably represented in the species as understood by most authors. This paper considers the species of Decaspermum in the Pacific and Australia. The Bismarck Archipelago is not included in this survey because the species that occurs there, D. urvillei (DC.) A. J. Scott comb.