Bauhinia

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Bauhinia

Description

Trees or shrubs (sometimes semiscandent), unarmed or with intrastipular spines (rarely shrubs with tendrils or thorns) or lianas with (rarely without) simple tendrils; branches terete or angular. Leaves entire, 2-lobate, or 2-foliolate, midrib with weakly to strongly developed secondary veins. Stipules various, deciduous or persistent; intrastipular tri- chomes variously developed, sometimes adpetiolarly enlarged and forming a spine. Flowers solitary or few to many in terminal or subterminal and axillary racemes, corymbs, or panicles (rarely cauliflorous), bisexual or rarely unisexual (polygamous or dioecious). Petals (1 — )5( — 6), white, various shades of red to purple, or yellow, subequal to greatly unequal. Fertile stamens 0-10; filaments connate (monadelphous or diadel- phous) or free, strongly to weakly declinate; anthers globose, ellipsoid to linear, opening by a longitudinal slit or a central pore in each theca. Reduced stamens or staminodes often present. Ovary 1- to many-ovuled; gynophore adnate with abaxial wall of hypanthium or free; style elongate or obsolete; stigma peltate, capitate or little differentiated from style. Fruits flat, suborbicular to broadly elliptic or obovate to linear, woody or thin- valved, dehiscent (often explosively) or indehiscent, continuous, filled, or septate within. Seeds orbicular to elliptical, endosperm present or absent.

Distribution

Asia-Tropical: all over the tropics: present
About 300 species all over the tropics. In Malesia 69 species.

Pollination

Little has been done to study the genus in nature. From Java (?) come reports on bat-pollination, which is also observed in S America. In several S American species bird-pollination has been observed, while the many medium- and small-flowered species with nectariferous discs probably are entomophilous. Butterfly pollination has been observed in some species in Thailand.

Anatomy

The stem anatomy has been studied in several species and particular attention has been paid to the anomalous growth of several of the large lianas, some producing band-shaped, winged and undulated stems ('monkey-ladders', 'escada das macacos'), due to the cambium being confined to two opposed areas, e.g. B. scandens. In B. vahlii successive rings of growths are found and in, e.g., B. championi a cleft xylem mass is found and one or two successive rings of xylem and phloem; secondary bundles arise in the pith.

Taxonomy

As this large genus comprises a wide range of life-forms from shrubs to trees and lianas and an unusual variation in flower structure some authors as, e.g., latest De Wit (1956) have found it evident to split it into several distinct genera. The present authors have studied the genus from all over its distribution area and found a reticulate pattern of variation. They have drawn the conclusion, now generally accepted among Legume-specialists, that Bauhinia in the sense of Linnaeus, Bentham, De Can- dolle, Taubert, and Hutchinson is an evolutionary unit and a very natural genus.

In the above only generic synonyms related to species occurring in the Malesian area have been mentioned. No less than 26 segregated genera have been created, see Wunderlin (1976) and Wunderlin, Larsen & Larsen (1987).

Cytology

2n = 24, 26, 28, 42, 56. About 40 species have been studied.

Citation

DC. - in Prodr. 1825: 512
de Wit - in Reinwardtia. 1956: 422.
de Wit - in Reinwardtia. 1956: 381
de Wit - in Reinwardtia. 1956: 418.
Wunderlin, Larsen & Larsen - in Polhill & Raven, Adv. Leg. Syst. 1. 1981: 114
de Wit - in Reinwardtia. 1956: 530.
Wunderlin - in Rhodora. 1976: 750
Wunderlin, Larsen & Larsen - in Biol. Skr. Dan. Vid. Selsk. 1987: 40
de Wit - in Reinwardtia. 1956: 135.
Taubert - in Engl. & Prantl, Nat. Pflanzenfam. 3, 3. 1891: 147
Watson & Dallwitz, Gen. Leg.-Caesalp. 1983: 12