Colvillea Bojer ex Hook., Bot. Mag. 61: t.3325 & t.3326. 1834.

Figs 67, 68, 70, 76

Type.

Colvillea racemosa Bojer ex Hook.

Description.

Unarmed, small to medium-sized trees, 8-15 (20) m and 50-70 (90) cm stem diameter (Fig. 67N); bark thin, pale grey, inner bark green. Stipules minute, setaceous and caducous. Leaves bipinnate, petiole glands absent, (6) 9-16 pairs of pinnae with (12) 15-30 pairs of oblong leaflets per pinna, apex rounded, base asymmetrical. Inflorescences suberect, large, robust, many-flowered terminal panicles, the secondary axes pendulous, pedicels jointed, bracts mostly caducous. Flowers bisexual, very distinctive, strongly zygomorphic and inverted (resupinate), bright orange (Fig. 68G); calyx of 5 subequal valvate segments, which are leathery and thickened, especially towards the tips, 4 of the segments fused for most of their length like a spadix; corolla with 5 reduced petals, the median petal (held lowermost in the flower) enclosed within the sepal cup, the lamina rolled into a nectar-containing conical receptacle; stamens 10, free, longer than petals, clustered curving out from the upper side of the inverted flower, anthers dorsifixed, glabrous; pollen in oblate tricolporate monads with coarsely reticulate surface ornamentation with sinuous, slightly convoluted muri; ovary short stipitate, flat, exserted beyond stamens. Fruits large, linear-oblong, pendulous, the valves partially separating allowing the seeds to be shaken out, the valves relatively thin-textured, strongly flattened and barely lignified (Fig. 70P). Seeds oblong-ovate, flattened.

Chromosome number.

2 n = 28 (Goldblatt 1981b).

Included species and geographic distribution.

Monospecific, endemic to western Madagascar (Fig. 76). Cultivated elsewhere, including in southern Africa.

Ecology.

Seasonally dry forests and spiny thickets. Trees are deciduous. The flowers are nectariferous and although often eaten by lemurs, they are pollinated by Siouimanga sunbirds (Du Puy and Rabevohitra 2002).

Etymology.

Named in honour of Sir Charles Colville (1770-1843), distinguished Scottish officer under Wellington in the Napoleonic wars and governor of Mauritius, 1828-1834.

Human uses.

Sometimes planted as an ornamental in villages (Fig. 67N).

Notes.

The status of Colvillea as a genus distinct from Delonix remains questionable as its placement either as sister to Delonix, or nested within it is unstable in phylogenies that have densely sampled Delonix (Haston et al. 2005; Babineau and Bruneau 2017), albeit in recent analyses based on larger gene sets Colvillea is clearly resolved as sister to Delonix (Kates et al. 2024). In contrast to Delonix, Colvillea has large terminal panicles of resupinate flowers with orange petals, four fused calyx segments and clustered stamens.

Taxonomic references.

Bojer (1834); Du Puy and Rabevohitra (2002) both with illustrations.