Phaseolus vulgaris (Wikimedia). One of the crop legumes experimented to explore its impact in Push-Pull Technology (see related article in Push-Pull Technology)

Phaseolus vulgaris, the common bean,^[2] string bean,^[3] field bean,^[3] flageolet bean,^[3] French bean,^[3] garden bean,^[3] haricot bean,^[3] pop bean,^[3] or snap bean,^[3] is a herbaceous annual plant grown worldwide for its edible fruit, either the dry seed or the unripe fruit, both of which are referred to as beans. The leaf is also occasionally used as avegetable, and the straw can be used for fodder. Along with other species of the bean genus (Phaseolus), it is classifiedbotanically into the legume family (Fabaceae), most of whose members acquire nitrogen through an association withrhizobia, a species of nitrogen-fixing bacteria.

Centrosema pubescens (Copyright: © 2010 by D. L. Nickrent (contact: This email address is being protected from spambots. You need JavaScript enabled to view it.) [ref. DOL20255] at PhytoImages.siu.edu)

Centrosema pubescens, common name centro or butterfly pea, is a legume in the family Fabaceae, subfamily Faboideae, and tribe Phaseolae. It is native to Central and South America and cultivated in other tropical areas as a forage for livestock.^[3][4]

Centro is a perennial herb that can reach a height of 45 cm (18 inches). The root system can reach up to 30 cm in depth, frequently in association withRhizobium, nitrogen-fixing bacteria.^[4] Stems grow and branch rapidly, producing a dense mass of branches and leaves on the soil. Stems do not become woody until about 18 months after planting. Leaves are trifoliate, with elliptical leaflets approximately 4  × 3.5 cm (1.6 × 1.4 inches), dark-green and glabrous above but whitish and densely tomentose below. Flowers are generally pale violet with darker violet veins, born in axillary racemes. Fruit is a flat, long, dark brown pod 7.5–15 cm (3–6 inches) long, containing up to 20 seeds. Seeds are spherical, about 4–mm (0.16–inches) in diameter, dark brown when ripe.

 
Calopogonium mucunoides (Photo from Wikimedia)

 Morphological description

A vigorous, creeping, twining or trailing, short-lived perennial herb, up to several metres long, forming a tangled mass of foliage 30-50 cm thick, with densely pilose stems with long rust-coloured hairs. Leaves trifoliolate, petiole up to 16 cm long, pilose; leaflets elliptical, ovate or rhomboid ovate, 4-10 cm x 2-5 cm, the laterals oblique, adpressed pilose or pubescent on both surfaces. Inflorescence a slender rust-coloured raceme, up to 20 cm long, covered with short, dense hairs; blue or purple flowers in fascicles of 2-6; bell-shaped calyx with five unequal lobes; corolla with emarginate standard, about 1 cm long. Pod linear-oblongoid, 2-4 cm x 3.5-5 mm, straight or curved, softly pilose with coarse reddish-brown hairs, impressed between the seeds. Seeds 3-8 per pod , compressed squarish, 2-3 mm long, yellowish or reddish-brown. There are 65,000-70,000 seeds/kg. 

 
Arachis pintoi growing under tree pantation [Photo copyright by Werner Stur (Tropical Forages): http://www.tropicalforages.info/]

Sixteen species were identified which are potentially useful, shade tolerant or shade adapted, pasture species for use beneath tree plantations in both the wet and the seasonally dry tropics. The most promising species suited to the wet tropics were Arachis pintoi, Centrosema acutifolium, C. macrocarpum, C. pubescens, Calopogonium mucunoides, Desmodium intortum, D. ovalifolium, D. canum, D. heterophyllum, D. uncinatum and Pueraria phaseoloides. The most promising species suited to the seasonally dry tropics were Arachis stenosperma, Centrosema brasilianum, Clitoria ternatea, Macroptilium atropurpureum and M. lathyroides.