Indigofera.
Family Fabaceae > Subfamily Faboideae > Tribe Indigofereae.
Plants of the World Online (Kew) accepts 730 species.
Australia has around 30 species of which 12 are found in S.E. Queensland.
Most species are small shrubs, a few are perennial herbs and rare small trees.
The branches are covered with silky hairs lying flat along the surface.
Typical hairs are ‘T’ shaped with a short base and equal or unequal arms.
There may also be stiff, simple multicellular hairs with or without glands.
The alternate leaves are on a petiole with often small stipules at the base.
The petiole has a pulvinus allowing the blade to move in response to stimuli.
Leaves are typically pinnate with an odd terminal leaflet.
Less common are simple or trifoliate leaves or pinnate leaves with an even number of leaflets and a pointed terminal extension of the midrib.
The usually opposite leaflets are on a petiolule that may have small stipels at the base.
Axillary inflorescences are a raceme or a spike.
(Racemes have solitary flowers, on a stalk (pedicel) along a midrib with the lower flowers opening first. Spikes are similar but the flowers have no pedicel.)
A few are panicles (branched racemes) or solitary flowers.
The bract below each flower usually falls off and there are no bracteoles.
The bell-shaped calyx has a tubular base with 5 sometimes unequal lobes.
The typical pea-shaped flowers, under 2 cm long have 5 petals.
The large upper standard petal has a narrowed or clawed base.
It is round or longer than wide with a mucro (short abrupt point) at the tip.
The 2 oblong wings at the sides are slightly adherent to the keel petals.
They may have a claw base and an auricle (ear-like appendage).
The bottom 2 erect keel petals are fused along their lower edges.
There is usually a spur near their short claw base that is fused to the wings.
There are some hairs on the bases of the petals.
Most flowers are shades of pink, mauve or red but there are white, purple, greenish or yellow ones.
There are 10 stamens with the filaments variously fused.
The stamen tube may be open along the upper surface opposite the standard petal.
The 10th or upper stamen may be free of the stamen tube.
Anthers, fixed at or near the base almost always have a glandular appendage.
The superior ovary has 1 to many ovules and the style has a head-like stigma.
The fruit are dehiscent linear, oblong or ovate pods a few mms thick.
They can be cylindrical, 4-angled or flattened in cross section.
They can also be curved, straight or sickle-shaped.
They open into 2 chambers usually along the upper suture only.
The 1 to many variously shaped seeds are separated by partitions.
Pods have hairs similar to those on the branches.
J.F.
