Genus Pterolobium

Author: R.Brown

Morphological description (Pterol densiflorum compl FM42 )
Lianas , climbing shrubs, scramblers, or small trees ; branchlets and (main) rachides often armed with recurved, paired or singular prickles.

Leaves spirally arranged, bipinnate, petioled; pinnae and pinnules opposite or subopposite, petiolulate. Stipules and stipels small, inconspicuous, caducous. Leaflets many, rather small, opposite or subopposite, subsessile, slightly emarginate at apex, unequal at base.

Inflorescences terminal or axillary, often paniculately aggregated recemes; bracts caducous, bracteoles absent.

Flowers bisexual, pedicelled, slightly zygomorphic. Hypanthium shortly cupular or discoid. Calyx lobes 5, imbricate, the lowest (exterior) one concave and larger. 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. Disk obscure or absent. 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. l 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.

Pods sessile or very shortly stipitate, compressed and samaroid, usually 1-seeded, indehiscent; basal seed-bearing part obliquely or broadly ellipsoid or ovoid; upper, wing-like part, membranous, obliquely more or less oblong or falcate, or elliptic, with slightly transversely curved, obscure or visible veins, one margin thickened and slightly straight, the other thin and slightly convex.

Seeds lenticular, flattened, smooth, exalbuminous.

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: Pterolobium borneense , Pterolobium densiflorum , Pterolobium macropterum , Pterolobium membranulaceum , andPterolobium microphyllum ).

In lowland forest, up to 500 m alt.; outside Malesia sometimes found at 500-1000 m, rarely up to 1500 m.

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, 1974: 2.