Range extension of the genus Pentastemona Steenis (Pentastemonaceae), endemic of Sumatra

Pentastemona Steenis (Pentastemonaceae) is known with two local endemic species, one in Central Sumatra (West Coast province), the other in northern Sumatra (southern Aceh province), i.e. both in areas West of the Barisan Mountain range. — Fig. 1. Additional material obviously belonging to Pentastemona was lately discovered among Epithema Blume (Gesneriaceae) borrowed from Harvard and Michigan herbaria by Dr. B.L. Burtt of Edinburgh, who was kind enough to send it to me for closer examination. It concerns four different gatherings by Rahmat si Boeea for H.H. Bartlett, made in or in the vicinity of the canyon-like course of the upper Asahan River, flowing to the East Coast, province Tapanuli (close to province North Sumatra), in northern Sumatra. The specimens had been named at the time by E.D. Merrill as Epithema saxatile Bl.?’, and filed as such.