The alluvial or wet prairies form the last and smallest division. They occur generally on the margins of water courses, though they are sometimes found with all their distinctive peculiarities, far from the points where waters run at present. They are commonly basins, and their outline is strongly marked; their soil is black, deep, friable, and wonderfully rich. Native grasses spring on them in singular luxuriance, rising to a great height, but they are too loamy for the cultivated grasses. In proper latitudes they are excellent for wheat and maize. Still more than the rolling prairies, they appear to the eye a dead level, though they have slight inclinations and depressions; yet from the general equality, and immense amount of vegetation, small ponds and bayous are formed there, which fill from the rivers and rains, and are only exhausted during the intense heats of summer, by evaporation. In the alluvial prairies that are connected with the rivers, these ponds are filled in the season of high waters with fish of various kinds; as the water becomes low, and their course connecting with the river become dry, the fish are taken by cartloads among the high grass, where the water is three or four feet deep. When the waters evaporate, the fish die, and thousands of buzzards are unable to prevent them from polluting the air. This decayed matter seriously affects the salubrity of the climate. Along these rich plains, herds of deer are seen, flying with the rapidity of the wind, or feeding quietly with the domestic cattle. In the spring and autumn, water-fowl in innumerable flocks hover about the ponds and lakes of these prairies, to feast on the oily seeds of the plants and grasses. During the months of vegetation, the richer prairies are blooming with flowers, of whose variety, number, forms, hues, and odors, description can furnish no adequate idea. Most of the prairie plants have tall and arrowy stems, with spiked or tassellated heads, and the flowers have great size, gaudiness and splendor, without much delicacy or fragrance. In the spring their prevailing color is bluish purple; in mid-summer, red mingled with yellow; in autumn, the flowers are large, generally of the helianthus shape, and of a rich golden color.