| + | The usual cultivated species of Vigna are annual bean-like rambling vines with 3 rhomboid-ovate stalked lfts., the lateral ones unequal-sided, the petioles long: fls. bean-like, white, pale to violet-purple and pale yellow, borne 2 or 3 together on the summit of a long axillary peduncle: pods slender, straight, or slightly curved, a few inches to 3 1/2 ft. long; seeds small, nearly round to kidney-shaped, bean-like, white or dark, self- colored or variously mottled, usually with a different color about the eye.—Species 60 or more, tropical. The species show great variation in stature and growth-habit, and particularly in the color of the seeds. The genus may be distinguished from Phaseolus by the fact that the keel is bent inward at right angles but is not coiled. Vigna resembles Dolichos in having a similar keel but differs from it in the form and position of the stigma. In the former species this is lateral, occupying a position just beneath the apex of the style and above the line of pubescence which extends up the inner face of this organ. Just opposite the stigma the apex of the style is bent backward and prolonged into a beak. The stigma in Dolichos, on the other hand, is terminal or merely oblique. The prolonged beak of the style is also absent. Vigna may be further distinguished from Dolichos in the shorter petioles of the first pair of aerial lvs. In Vigna these are about 1/4 in. long or shorter, whereas in Dolichos they are 1 in. long or longer. |
| + | Three species of Vigna are in common cultivation: the cowpea, V. sinensis; the catjang, V. Catjang; and the asparagus bean, V. sesquipedalis. The asparagus bean (V. sesquipedalis) can be used as a forage plant for stock, or the green pods may be cooked as a snap bean since they are more tender and brittle than those of the cowpea or catjang. This species is little grown, however, due to a lack of productivity, except as a curiosity or novelty. The nomenclature of the cultivated varieties of the cowpea and catjang is almost hopelessly confused. Piper enumerates 220 agricultural varieties of the former and 50 of the latter. Formerly the name cowpea was restricted to the buff-colored or clay-pea, but it is now commonly used generically; it is an Americanism. Common generic terms now in use in the South are "black-eyed pea" and "corn-field pea." While the cowpea and the catjang are now employed mostly for animal food and green-manuring, the pea itself is a good human food and has been so used for many years. For table use the peas are best gathered when the pods first begin to change color; however, they are most extensively used from the dry ripe pods. As long ago as 1855 an excellent essay on cowpeas was written by Edmund Ruffin ("Essays and Notes on Agriculture," Richmond, 1855). Piper (Bulletin No. 229, Bureau of Plant Industry, United States Department of Agriculture) describes these three species as follows: |