Lianas, climbing shrubs, scramblers, or small trees; branchlets and (main) rachides often armed with recurved, paired or singular prickles. Leaves spiral, bipinnate, petioled; pinnae and pinnules opposite or subopposite, petiolulate. Stipules and stipels small, inconspicuous, caducous. Inflorescences terminal or axillary, often paniculately aggregated racemes; bracts caducous, bracteoles absent. Flowers bisexual, pedicelled, slightly zygomorphic. Petals 5 (usually 4 similar and 1 different, all similar in P. borneense), imbricate, the standard (superior, interior one) often slightly contracted and the margins slightly inflexed near the middle. Stamens 10, all fertile, free, in one whorl; filaments usually alternately long and short in buds but equal in length in open flowers; anthers oblong, c. 1 mm long, dorsifixed, introrse. Ovary sessile or stipitate, free, ellipsoid, slightly flattened and curved, 1- or 2-ovuled; style filiform; stigma small, round, truncate or slightly concave. Seeds lenticular, flattened, smooth, exalbuminous.
Asia-Temperate: Asia-Tropical:, Borneo present; India present; Jawa (Jawa present); Lesser Sunda Is. present; Malaya (Peninsular Malaysia present); Philippines (Philippines present); Sumatera (Sumatera present); Thailand (Thailand present) Burma: present S & E Africa: present Yemen: present
A genus consisting of about 11 species, distributed in the Old World: S & E Africa, Arabia (Yemen) (only 1 sp.), India (1 sp.), China (c. 2 spp.), Burma, Thailand and Indochina (4 spp.); Malesia (5 spp. in Sumatra, Malay Peninsula, Borneo, Java, Philippines, Lesser Sunda Islands).
The genus Pterolobium is closely related to Caesalpinia (incl. Mezoneuron). It can be distinguished from the latter by 1) the pods samaroid or with a well developed terminal wing (against pods wingless, with a rudimentary wing, or with a narrow, lateral wing), and 2) ovary slightly curved (against ovary rectilinear). See J.E. Vidal & Hul Thol, I.e.