New species of the genus Bulbophyllum (Orchidaceae) from Sumatra, Borneo, and Papua New Guinea

Nineteen new species of the genus Bulbophyllum Thouars (Orchidaceae) are described. They originate from Sumatra (including the Riau Archipelago), Borneo, and Papua New Guinea. Five species belong to sect. Hirtula Ridl., four to sect. Leptopus Schltr., three to sect. Hybochilus Schltr., two to sect. Sestochilus (Breda) Benth. & Hook.f., and one to the sections Cirrhopetalum (Lindl.) Rchb.f., Epicrianthes (Blume) Benth. & Hook, f., and Monilibulbus J.J. Sm. each. Two more species cannot be assigned to any section with certainty; one of these may belong to sect. Desmosanthes (Blume) J. J. Sm. The other shows similarity to B. bisetum Lindl. and B. bisetoides Seidenf.; these three species together may well constitute a separate section.