II. BALIZIA Barneby & Grimes
Balizia Barneby & Grimes, gen. nov., inter affinia floribus uniuscujusque capituli more Albiziae heter- omorphis instructa his notulis praestans: rami indeterminati, ultra flores producti; foliola penninervia; capituli flores peripherici pedicellati, umbelliformes vel quasi corymbiformes; ovarium apice truncatum; legumen lignosum, tarde folliculare vel indehiscens, intus septatum sed haud lomentiforme. — Sp. typica: Balizia pedicellaris (de Candolle) Barneby & Grimes = Inga pedicellaris de Candolle = Pithecolobium pedicellare (de Candolle) Bentham. — Etymology: anagram of Albizia.
Pithecolobium sect. Samanea ser. Carnosae Bentham, 1875: 587, minima ex parte (sp. no. 64).
Unarmed trees, either macro- or microphyllidious, attaining 30-45 m but flowering at 10 m upward, the fertile branches indeterminate, the inflorescence composed of umbelliform capitula or corymbiform racemes arising singly or fasciculate in the axil of either coeval or hysteranthous lvs. Indumentum of young stems and lf-axes composed of short simple, usually sordid or brown hairs. Stipules linear-lanceolate or ligulate, externally nerveless, caducous (? sometimes obsolete). Lf-formula iii—xv/5—33; petiolar nectaries sessile or shortly stipitate, the first situated either near midpetiole or between pinnae of first pinna-pair; lft- pulvinules <2 mm; largest lfts 6-45 mm; venation of lfts pinnate, the midrib not or scarcely excentric. Receptacle of capitula, including terminal pedestal, 1.5-4.5 mm; bracts small caducous; fls dimorphic, the peripheral ones slenderly pedicellate, mostly bisexual, the longer pedicels 2.5-10 mm, the terminal fl larger than the rest and functionally sterile; perianth of peripheral fls 5-merous (random anomalies), the calyx (2-)2.3-5 mm, the corolla 5.5-10 mm; androecium of peripheral fls 12-26-merous, 17-36 mm, the filaments white, greenish white, or roseate; ovary truncate at apex; ovules 10-20. Pods of two types (further described in conspectus of species): (a) woody, piano-compressed, transversely fibrous, tardily follicular, and (b) ligneous, plumply compressed, indehiscent; seeds horizontal on subfiliform or ribbonlike, somewhat contorted funicle, narrowly oblong, the testa either putty-colored and rather discolored within the pleurogram or partly white and partly translucent, pleurogram narrowly U-shaped; the embryo green or anthocyanic (pink or orange). — Spp. 3, one widespread in the Orinoco and Amazon basins, the Guianas, and extending S in Atlantic forest of Brazil to Paraná, one bicentric in lower Amazonia and Central America, one localized in Gulf-Caribbean forest of Belize and adjoining republics.
Balizia and Hydrochorea, next above, are newly defined segregates from Pithecellobium sensu Bentham or from Albizia sensu Nielsen; because of their evident close kinship they can profitably be discussed together. In flower, the two genera closely resemble Albizia, but are distinguished from Albizia, as we understand it, by indeterminate inflorescence-axis and vegetative branches arising from sylleptic and proleptic buds (as opposed to proleptic buds only), and further from the native American species of Albizia (sect. Arthrosamanea) by pinnate leaflet-venation and truncate ovary. In gross aspect and almost all technical features, flowering specimens of Balizia and Hydrochorea are essentially indistinguishable from Abarema, or from each other for that matter, but their fruits are fundamentally different, so much so as to have prompted contradictory alignments within tribe Ingeae and repeated shifts of particular species from genus to genus. Thus Balizia pedicellaris, first described as an Inga, has been transferred successively to Pithecellobium, Samanea, and Macrosamanea; B. leucocalyx, described (because of its thick-walled indehiscent fruit) as a Samanea, has been removed to Pithecellobium and, inferentially, to Albizia sensu Nielsen; and Hydrochorea corymbosa has been classified in turn in the genera Mimosa, Pithecellobium, Arthrosamanea, and Cathormion, emphasis being laid always on the lomentiform fruit as the generic signature.
Balizia and Hydrochorea are conjectured to have arisen from common ancestry and to have diverged principally by evolution of different dispersal strategies and pari passu of distinctive pod morphologies. The ligneous fruits of genus Balizia are indehiscent or tardily dehiscent, their seeds being released sometimes only after decay of the valves, on the floor of terra firme forest, whereas the lomentiform fruits of riparian Hydrochorea are adapted to dispersal by water. Although fruits of Hydrochorea recall those of some species of Albizia sect. Arthrosamanea adapted to similar riparian habitats, the plants, as already stated, are significantly different in form of inflorescence, leaflet-venation, and shape of ovary.