A Southern Legume.--The soils of the cold north are protected from leaching during the winter by the action of frost. The plant-food is locked up safely for another year when nature ceases her work of production for the year. Farther south, in the center of the corn belt, there are leaching periods in fall and spring and oftentimes during the winter, but winter wheat thrives and, in ordinary crop-rotations, covers much of the land that might otherwise lose plant-food. As we pass from the northern to the southern states, the preservation of soil fertility grows more difficult and at the same time the restoration of humus becomes easier. The heat makes easy the change of organic matter to soluble forms, and the rains cause waste, but the climate favors plants that replace rapidly what is lost. In the work of supplying land with fertility, directly and indirectly, the southern cowpea has an important place. It is to the south what red clover is to the north, and it overlaps part of the red-clover belt, having a rightful place as far north as the Ohio Valley, and portions of Pennsylvania. Characteristics.--The cowpea is closely related to the bean, and is very unlike the Canada pea, which is a true pea, thriving only in a cool climate. The cowpea has been grown in the southern states over one hundred years, and the acreage is large, but it never has come into the full use it deserves. Being a legume, it stores up nitrogen taken from the air, and unlike red clover it makes its full growth within a short period of time. It can grow on land too infertile for most kinds of valuable plants, and on better land. The vines can crowd out nearly all varieties of weeds. The roots go to a good depth and are thickly covered with the nodules of nitrogen-gathering bacteria. Varieties.--There are many varieties of the cowpea, and confusion of names prevails, although some stations have done good service in identification of individuals carrying a number of names. The very quick-maturing varieties adapted to northern conditions do not make as much foliage as the rank-growing ones that require a relatively long season, but some of them are heavy producers of seed. There are varieties requiring six months of southern heat to bring them to maturity, and some failures attending the introduction of the cowpea into more northern latitudes have been due to bad selection. A few varieties reach maturity within two months of hot weather. The trailing habit is affected by the soil, the bunch varieties tending to trail when grown on fertile land. When the crop is wanted for seed, the peas that do not trail heavily will prove more satisfactory. The selection of variety is a matter of latitude and purpose, exactly as it is with corn.