Of the bunch grasses the _Poas_ are by far the most abundant. Of this genus nine species were obtained, but this gives an inadequate idea of the variety. Of one species alone Dr. Vasey has enumerated nine varieties, and advances the opinion that several will be eventually considered as species. They are found at all altitudes, mostly on the slopes. Perhaps the most important single species in that region is the _Bouteloua oligostachya_, the so called “Circle grass”. It has a peculiar habit of forming partial or complete circles on the ground, with areas of bare ground in the center. These turfy rings are comparatively narrow, often not more than three or four inches in width, while the circles are from two to four feet in diameter. The form is not always circular, but often assumes irregular shapes. The grass is sweet and nutritious, but its chief value consists in its power to resist inclement seasons, as it cures standing, like the “Buffalo grass” of the Great Plains. Another very valuable grass is the _Eriocoma cuspidata_, which is known by the name of “Sand grass”. It grows at much lower altitudes, and is properly a valley grass. It has a solitary, scattering habit, or at least the bunches are small and turfless. Horses and cattle select it with care from among other species, and it seems especially nutritious. It has a large black grain, which is often collected by the Indians for food. A remarkable lowland grass is the Vilfa (_Sporobolis airoides_). It has something of the appearance of “Hair grass”, with a widely spreading purple panicle and large perennial roots. The old culms persist at the base, and with the new ones form thick and almost woody tufts. These tufts are scattered about in the strongly alkaline soils of the river bottoms, and are extensively pastured by large herds of cattle. A marked characteristic of this grass, common, however, to several others, is its power to take up saline matter, which gives to the whole plant a salty taste. The effect of this upon the stock feeding upon it is doubtful, judging from the conflicting reports of the inhabitants; but it seems that when cattle are first pastured upon it they are injured by the excess of salt, but that after a time they cease to be injured by it. All of the so called “Salt grasses” are cropped to a greater or less extent by stock. The chief grasses of the elevated timber tracts belong to the genus _Bromus_. When young they are good, but they become stale and valueless with age. The only grass that can compare with those of the eastern meadows, and which forms a continuous sod and covers the ground with a uniform growth, is a variety of _Aira cæspitosa_, a red topped grass, which was found surrounding the small lakes of the mountains and plateaus, at elevations of 11,000 feet and over. This is an exceedingly beautiful grass as it waves in the gentle breezes that fan the lakelets of the upper regions.