Centrosema (A.P. de Candolle) Bentham.
A genus of about 40 species, perennial vining herbs, of tropical and warm temperate regions of the Western Hemisphere.
ID notes:Centrosema and Clitoria are unique among our legumes in having resupinate flowers, the pedicel twisted 180 degrees so that the large “standard” is lowermost. They are often confused; the following key includes both genera for easier differentiation. The two widespread Southeastern United States species Clitoria mariana and Centrosema virginianum are especially often confused when vegetative (see key for easy distinctions when in flower or fruit). Clitoria mariana has the upper leaf surface glabrous (vs. uncinulate, and thus tacky to the touch, sticking lightly to skin or fabric, in Centrosema virginianum), the terminal leaflet broadest 0.3-0.5× of the distance from the leaflet base to leaflet apex (vs. Centrosema virginianum broadest at 0.1-0.4×), terminal leaflet with 4-5 or fewer main veins on each side of the midvein (vs. 5-7, or more in Centrosema virginianum var. angustifolium), the apex blunter (vs. more acute), the venation less raised and reticulated on the lower leaflet surface (vs. more obviously raised-reticulated), and the color of the leaf bluer (vs. greener).