Family Fabaceae > Subfamily Faboideae.
Sigmoidotropis speciosa is the type species for the genus.
It was previously in the Phaseolus then Vigna genera.
Common names include Snail or Corkscrew Vine and the Wandering Cowpea.
Used as an ornamental vine it is from tropical areas of South and Central America.
It is a perennial vine that grows from underground tubers.
Stems, up to around 5 m long climb by twining and scrambling.
Young stems have dense hairs and older ones may become woody.
Leaves, on a hairy petiole up to 8 cm long have 3 leaflets.
Stipules, 3 mm long at the petiole base have a pointed tip.
Leaflets are on a short stalk (petiolule) with stipels that fall early.
The leaflets are up to around 10 cm long and 4 (6) cm wide.
They can be ovate to diamond-shaped (rhombic).
The base is rounded and the tip tapers to a point.
The lower surface almost always has dense hairs, the upper few or none.
Inflorescences, including the peduncle are up to 30 cm long.
Projecting well past the leaves are the 1 to 3 clustered flowers.
Flowers, 3 to 4 cm long are on a stalk (pedicel) around 3 mm long.
The pedicel has tiny elliptic or ovate bracteoles on it.
The wide bell-shaped calyx is 6 to 10 mm long.
The 2 short upper lobes are fused.
The 3 pointed lower lobes or teeth are around 4 mm.
The outer surface can be smooth or have short soft hairs.
There are 5 pale purple or bluish-purple petals in the corolla.
The large erect upper standard or banner petal is semi-circular.
The 2 narrow side wing petals, almost as long have a claw base.
The 2 partly fused lower petals form the keel with a wide base and narrow tip.
It coils up into a single circle.
The bases of the petals, and tip of the keel may have some yellow or white.
The stamens, ovary and style lie in the coiled keel.
Nine of the 10 stamen filament bases are fused into a tube.
The tenth upper or posterior stamen is free.
The green ovary and its long style lie in the keel.
The tip of the style, with long hairs lies in the slit at the tip of the keel.
Fruit are a linear legume or pod 10 to almost 20 cm long and 0.5 cm wide.
They are compressed sideways and can be smooth or have a few hairs.
Each has up to 20 oblong or kidney-shaped seeds around 6 mm long.
J.F.
