Medicago.
Family Fabaceae > Subfamily Faboideae > Tribe Trifolieae.
The Clover tribe usually includes Medicago, Melilotus and Trifolium but it is still uncertain which of these and other genera belong in it.
These all have flowers with a trigger mechanism for pollinatioin.
Plants of the World Online recognises 91 species while others have 85 to 105.
Australia has around 14 naturalised Medicago species.
They are commonly seen as a weed in lawns.
There are a few shrubs to 1 m high but almost all are annual or perennial herbs.
The herbs have branching prostrate stems with erect ones to around 30 cm.
Apart from their fruit they are similar to clovers (Trifolium).
The alternate leaves, on a petiole have 3 pinnate leaflets.
The stipules at the petiole base are partly fused to it.
Their upper edge is deeply cut into pointed lobes or teeth.
The obovate leaflets are around 12 mm long and up to around 8 mm wide.
The tip has a mucro (small abrupt point) and the adjacent edge has teeth.
There may be no hairs or some on the lower surface.
Axillary inflorescences are on a peduncle.
The few to many flowers may be attached to the peduncle tip (umbels) or along a short midrib (raceme).
There are short 1 mm bracts at the peduncle base.
Flowers are on a 2 to 3 mm long pedicel.
The bell-shaped calyx has 5 teeth of the same or different lengths.
The almost always yellow flowers have an obovate standard petal.
Up to around 1 cm long it is usually erect.
The 2 wing petals have a long hooked appendage on the upper edge.
The wings fit tightly around the shorter keel petals.
The hook is involved in the explosive opening of the flower for pollination.
Nine of the stamens are fused into a tube with free ends of different lengths.
The upper or 10th stamen is free.
The stamen tube, enclosing the ovary and style bends up near the end.
The ovary, sometimes on a short stalk has 1 to numerous ovules.
The style has a large stigma.
The mostly indehiscent pods are typically tightly coiled.
With 1 or 2 pods they are disc-like and with more they become cylindrical or conical.
The surface can be smooth or nodular and may have spines along the suture.
Pods, with 1 to many seeds may have hairs that lie flat along the surface.
The calyx remains attached.
J.F.
