Plectocomia

Abstract: Summary. Morphology, natural history and ecology of the rattan genus Korthalsia Bl. are discussed prior to a synopsis of all species. K. jala and K. furtadoana are described as new. Areas of synonymy and nomenclatural and taxonomic confusion are discussed. Korthalsia is a genus of climbing palms belonging to the Lepidocaryoid Major Group (Moore 1973); its distribution is centred on the perhumid areas of the Sunda Shelf with outliers to the north as far as Indochina, Burma and the Andaman Islands, and with three species being found east of Wallace's Line. It is morphologically a very distinctive and well-circumscribed genus, markedly different in many features from the other Asiatic rattan genera. Many of its species are widespread and abundant in Southeast Asia. Yet for all its distinctiveness, the genus has proved to be extraordinarily intractable to taxonomic research; quite apart from the problems with which the rattan taxonomist is already familiar (such as badly collected specimens, mixing of numbers and hiding of all genera in 'Calamus' in herbaria), Korthalsia has a further dimension of awkwardness, which is related to the flowering behaviour. Flowering in Korthalsia is hapaxanthic, i.e. individual stems produce inflorescences from the topmost nodes and then die; unlike the other Asiatic hapaxanthic rattans such as Plectocomia, Plectocomiopsis and Myrialepis (for full list see Dransfield 1978), stems of Korthalsia not only sucker basally, but branch aerially, and the vast aerial entanglement of stems often proves too difficult to be pulled out of the forest canopy. So, even if inflorescences can be spied from the forest floor, the combined strength of 4 or 5 men pulling may be insufficient to pull down the flowers or may result in the snapping of the stem. There is also some evidence that Korthalsia species flower rather infrequently. If an inflorescence is obtained, this will represent only one stage of the development of flowers or fruit-a very different situation from many rattans belonging to other genera where a single stem of a pistillate plant may furnish herbarium material, admittedly only of one sex, but representing all stages from bud to mature fruit. Despite these problems, we do have material representing the morphology of the widespread species except, perhaps, for K. fiagellaris. The local species, however, are very poorly represented. For example, in 1975 I found a most extraordinary aberrant new species (K. jala described below) in Sarawak, in the sterile state; however, it was not until 1979 after pulling stems on successive expeditions to Borneo that I was able to obtain fertile material. K. cheb is another such local species; described by Beccari in 1884 based on sterile material, it was not until 1968 that inflorescences were obtained, and to my knowledge have rarely been collected since. Fortunately, most species in the genus show greater disjunction in vegetative features than in inflorescence details, so that most species may be identified from sterile material only.