Page:Popular Science Monthly Volume 80.djvu/230

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is exposed to the wind, the blowing soil frequently prevents the growth of field crops or any other plants.

The flora of the dry valleys is very similar to that of the prairie regions of the state, being especially rich in grasses. The principal widely distributed plants of the dry valley are: switch grass (Panicum virgatum), wheat grass (Agropyrum pseudo-repens), blue joint grass (Calamagrostis canadensis), wild rye grass (Elymus canadensis), red top (Agrostis alba), tickle grass (Agrostis hiemalis), rattlesnake grass (Panicularia americana), and a number of sedges (Carex trichocarpa, C. filiformis, etc.). All of these species are valuable forage plants and they are all included in most of the hay that is put up from the valleys. Besides these economic plants there are many other herbaceous members of the prairie flora that have wandered into the Sand Hills and have found congenial homes in these dry valleys.

PSM V80 D230 Rim of blowout with fringe roots and the slipping sands.png

Fig. 12. The Rim of a Blow-out with the Fringe of Roots and the Slipping Sands.

The river flats properly belong to the dry valley type, since here we find a soil free from surface water and with all of the above species of plants often growing in profusion. These low flat areas extend from the banks of the river back sometimes several hundred yards to the bases of the hills. These flats or "benches" are well developed along the Middle Loup River. The river winds across the flats in a very irregular course, sometimes cutting close to the hills on one side and then shooting across to the hills on the opposite side of the flat. On these flats and along the bank close to the stream occur the most of the trees of the region. Thickets of plum (Prunus americana), and cherry