Large woody climbers with all parts bearing white latex. Branchlets weakly lenticellate or not, pubescent at least when young. Leaves opposite; Inflorescence an umbelliform panicle formed from terminal and axillary cymes; Sepals with colleters in a row at base inside, only at edges of sepals at base inside or without colleters. Stamens inserted in lower half of tube or almost in the middle of tube; Fruit of paired follicles; Seeds consisting of a flattened grain and a coma directed towards the fruit apex.
Asia-Tropical, continental Southeast Asia present, western Malesia present
5 species in continental Southeast Asia and western Malesia. In Malesia 3 species.
The species in this genus are somewhat heterogeneous and possibly do not form a monophyletic group.
D.J. Middleton - in Fl. Thailand. 1999: 118
K. Schum. - in Engl. & Prantl, Nat. Pflanzenfam. 4. 1895: 178
Wight - in Harvard Pap. Bot. 2005: 68
Pit. - in Lecomte, Fl. Indo-Chine 3. 1933: 1232
Wight - in Tree Fl. Sabah & Sarawak. 2004: 12
Pichon - in Mém. Mus. Natl. Hist. Nat. 1950: 103
Benth. & Hook.f. - in Gen. Pl. 1876: 717