As Prof. Bremekamp has dealt with the genus Pleiocraterium from the taxonomic point of view, I intend to supplement his exposition here with some observations on the ecology of these remarkable additions to the Malaysian mountain flora. Some of these observations have been included already in a general report on the results of the Losir expedition published in Dutch. As a further illustration I am giving two photographs taken from one of the two Sumatran species in its natural habitat. Altitude. Both species were found on the highest parts of the mountains only, viz. Pl. gentianifolium just below the summit of Mt Goh Lembuh, and Pl. sumatranum between our camp at the base of the central Peak of Mt Losir at c. 3250 m. and the summit of the latter at 3460 m. These two mountains lie rather far apart: Mt Losir is the highest top of the Barisan Range proper, whereas Mt Goh Lembuh is a more isolated mountain, rising c. 50 km. NNE of Mt Losir and separated from the latter by a wide depression. The two mountains also differ geologically.