TREFOIL (OF. trifoil, trefeul, Fr. trefic, from Lat. trifolium, trefoil, three-leaved, from fres, three + fotium, leaf), BIRD'S-FOOT ( LO ) . A genus of plants of the natural order Legu minosne. The pods are cylindrical, somewhat spongy within and imperfectly divided into many cells. The name Idrd's-foot trefoil is derived from the resemblance of the clusters of pods to a bird's font. The numerous species are natives of the temperate and colder regions of the Old World. The common bird's-foot trefoil (Lotus eornieulatas) is common in European pastures. The spreading decumbent stems, 4 to 16 inches long, arise from a short, thick rhizome and bear umbel-like cynics of five to ten yellow flowers. which have a rich, honey-like odor. The leaves have three obovate leaflets, and at the base of each leafstalk there are two large leaf-like ovate stipules. The plant is by some regarded roi the shamrock (q.v.) of Ireland. It is nutritious and much liked while young by all kinds of stock.
It has been introduced into the United States, where it is common, especially in the South. A larger species, very similar, with stein nearly erect, more compact heads of smaller flowers, and much smaller seeds, is the greater or narrow leaved bird's-foot trefoil (Lotus major) of much the same range. The characteristic dif ferences remain under cultivation in every va riety of soil and situation. Marsh bird's-foot trefoil (Lotus vliginosns) is a species common in damp meadows. The winged pea (Lotus Tetragonolobus), remarkable for four mem branous wings which run along its pods, is a native of Southern Europe, where it is grown for salads and as an ornamental plant. It is cultivated in the United States mainly as a forage plant and a winter crop for plowing under in spring as green manure. In some parts of Europe its seeds are used as a substitute for coffee.