Dendrobium (Sect. Pedilonum) purpureum Roxb. (Orchidaceae) and Its Allies

Abstract

Summary. Detailed morphological investigations have shown that the name Dendrobium purpureum Roxb. has been applied at various times to six distinct taxa: D. capituliflorum Rolfe, D. catillare Rchb. f., D. constrictum J. J. Sm., D. kraemeri Schltr., D. morrisonii Schltr. and D. purpureum Roxb. The name D. catillare has itself been misapplied to a species which is here described under the new name D. taveuniense. D. purpureum var. candidulum Rchb. f. is here raised to the level of subspecies. Each taxon is described and illustrated and a key is provided for their identification. Whilst revising section Pedilonum (Blume) Lindl. of the genus Dendrobium Sw., it has become apparent that the name Dendrobium purpureum Roxb. has been applied to material from Sulawesi to Samoa and from Palau to Vanuatu, which varies greatly in both floral and vegetative characters. The nature of this variation indicates that the name D. purpureum has been used for six distinct species. Detailed examination of type material has also shown that the name of one of these species, D. catillare Rchb. f., has itself been misapplied. A new species, D. taveuniense Dauncey & P. J. Cribb, is therefore described. The following account outlines the nomenclatural history, defines the species involved and shows how they differ from each other. The confusion between these seven species has several origins. The scarcity of material from the Moluccas, the type locality of D. purpureum, has led to a poor understanding of that species. Much of the synonymy has been proposed by botanists working on regional floras who did not have access to all type material and who had an incomplete understanding of the related species in other geo- graphical areas. The use of flower colour without reference to floral morphology has probably been a major cause of confusion. Finally, the vegetative morphology of the taxa is quite similar.