Caesalpiniaceae > Subfamily Caesalpinioideae.
Plants of the World Online (Kew) currently recognises 294 species.
Many are native to Central and southern America especially Peru, Ecuador and Colombia.
Uses include as nitrogen fixers in soil, a food and as a shade or ornamental tree.
Most are trees up to 15 metres with some 25 to 30 m and there are some shrubs.
Small 4-angled twigs have dense rust-coloured hairs.
Larger branches are round in cross section and have few or no hairs.
All have small pale spots (lenticels or pores).
The medium to large leaves are alternate and in 2 ranks.
They are once divided (pinnate) with a pair of leaflets at the tip (paripinnate).
Leaves are on a short petiole with small stipules at the base that fall off early.
The short to long leaf midrib (rachis) often has wings down the sides.
Along the midrib are 1 to 10 opposite pairs of leaflets on short, or no petiolules.
On the upper surface of the midrib and between each pair of leaflets is 1 (or more) gland.
The nectar secreting glands are usually directly attached but some are on a stalk.
There are often hairs on all parts of the leaves.
The veins are prominent on the lower leaflet surface.
The mostly axillary inflorescences# can be a spike, a raceme, small head or umbel-like.
There may be almost no peduncle up to a long one.
The typically small bracts at the base of the peduncle fall early.
Flowers are directly attached (sessile) or on a stalk (pedicel).
Where there is a pedicel it is mostly short but a few species have a longer one.
There are hairs on the peduncle, bracts, midrib and pedicels.
The calyx, and the usually larger corolla both have a tubular base with 5 small teeth or lobes.
Both have hairs on the outer surface.
The white petals may have a greenish or yellowish tint.
There are numerous, sometimes hundreds of stamens.
Around half the length of the filaments are fused into a stamen tube.
The free sections are of different lengths but most extend well past the petals.
The smooth or hairy ovary has a few ovules.
The long style may extend slightly past the stamens.
The small stigma may be spherical or lobed.
The fruit are a legume or pod mostly under 30 cm long but some are up to 1 or 2 m.
The mostly indehiscent, smooth or hairy pods can be leathery or woody.
They are variously shaped being flattened sideways, 4-angled to almost round in cross section.
Straight or curved pods can be linear, oblong and coiled or twisted and they usually have thickened sutures.
They mature from green to a reddish or yellowish-brown.
The oblong black seeds are surrounded by a white fleshy layer.
# Spikes have flowers with no, or a very short stalk, along a midrib with the lower ones opening first.
In a raceme the flowers are on a stalk (pedicel) but the terms are not always strictly used.
Where a few spikes or racemes are in very close axils the inflorescences can appear to be branched (panicles).
Heads, roughly spherical, have densely packed flowers along a short central axis.
Umbel-like inflorescences have flowers all attached to the tip of a branch.
J.F.
