I found this citation on the book Legumes of Bahia:
"von Reis Altschul in Contributions to the Grey Herbarium 193: 1-65 (1964) (revision of the genus includinh a key to the taxa).
2 species in West Indies and northern South America
1 Anthers eglandular in bud; involucre or scar 3/4 of the way up the peduncle; legume scurfy to verrucose, and dull......................
A. peregrina1 Anthers glandular in bud; involucre just below the recptacle; legume smooth to reticulate, and nitid (
A. colubrina):
2 Leaflets linear with the mid-vein more proeminent than secondary venation; inflorescences paniculate in the branch apices; heads whitish in bud involucre with tips extended and noticeable below the immature head; legume very elongated, regularly contracted...................
var. colubrina 2 Leaflets dilated in the middle, with proeminent secondary venation; inflorescences fasciculate in the leaf axils and subterminal, or racemose in the branch apices; heads not whitish in bud; involucre a narrow band, obscure; legume usually relatively short and wide, often irregularly contracted...................
var. cebil"
A little glossary with some botanical terms:
Eglandular: that doesn't has secretive structures (glands);
Anther: adroecium (masculine part of the flower) structure that contains the polen;
Leaflet: each subdivision of a compound leaf, that resembles an entire leaf, bud doesn't has an axillary bud.
Glandular: that has secretive structures (glands);
Legume: the fruit of the Fabaceae family;
Dull: that doesn't show brightness;
Peduncle: the basis of the inflorescence;
Reticulate: the surface resembles a reticulum (network);
Scurfy: that has a rough and irregular surface;
Venation: veins arrangement pattern;