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Show 232 Colorado, but, when the valleys of the streams are cultivated, will become as plenty and as troublesome as upon the eastern slope. The vegetation of the valleys of Southwestern Colorado was free from the effects of irrigation, cultivation, and large herds of cattle and sheep, all of which rapidly produce great changes. As before mentioned, the flora of Southern and Southwestern Colorado above timber- line is nearly the same as the alpine floras of Central and Northern Colorado. From timber- line ( 11,000 to 12,000 feet altitude) down to 8,000 feet altitude, the effects of latitude and longitude are barely noticeable upon the flora. As we approach New Mexico, but very few plants of a more southern habitat appear, and very few of those common in Northern Colorado are absent. The western slope produces very few plants of a more western habitat until altitudes below 8,000 feet have been reached. Below this altitude are found the somewhat distinct floras of the different parts of Colorado. The flora below 8,000 feet, north of the divide between the Platte and Arkansas Bivers, is in greater part found southward in the parks and valleys along the base of the mountains. It contains the greater number of species of Astragalus, thirty species growing, where, upon an equal area southward and westward, not more than half a dozen can be found. As we cross the divide and come into the valley of the Arkansas, a difference in the aspect of the vegetation is at once noticed. This is the cactus- center of Colorado. Mentzelia is magnificently represented by seven species. The Nyctaginaeece are nearly as well developed as in Southwestern Colorado, while Solanacece and Euphorbiacecc are much better represented. Many plants of southern habitat, as Zinnia, Melam-podium, Ximenesia, Tricuspis, & c, become quite conspicuous, and many stragglers of the south here grow in their most northern location. San Luis Valley, an elevated plain ( 7,000 to 9,000 feet altitude), does not possess the different conditions necessary to the growth of an extensive flora. The alkaline flats produce an abundance of Chenopodiaceoe. Many interesting plants undoubtedly grow along the boundaries of the park and the edges of the mountains. Its southern portion on the Rio Grande ( altitude 7,000) has, in a very limited degree, the appearance of a New Mexican flora. The number of the phsenogamous plants growing in Southwestern Colorado will not equal the 900 species that can be found upon any similar area upon the eastern slope. The impressions received by any one who has noticed the flora of the eastern slope, riding rapidly over Southwestern Colorado, below 8,000 feet altitude, are, the great scarcity of all vegetation; the comparative abundance of rosaceous shrubs, and Artemisia tridentata ; the great number of the annual species of Urioganum; the showy blossoms of Malvam; the few species of Astragalus and Pentstemon. LIST OF PLANTS OF COLORADO NOT MENTIONED IN THE SYNOPSIS OF THE FLORA OF COLORADO, MISCELLANEOUS PUBLICATIONS, No. 4. Thanks are due to Dr. Asa Gray for descriptions of new species and determinations of many plants of the collection; to Dr. George Engel-mann for hid descriptions of new species and determinations of Cacti-cecc9 Loranthaeece, and species of other orders; to Mr. S. Watson for determinations.; to Prof. Thomas C. Porter for determinations of plants from the vicinity of Canon City; and to Prof. D. C. Eaton for herbariaw facilities and assistance; to Mr. Engene A. Rau for the list of Musci and Hepaticce ; and to Mr. J. H. Bedfield for much assistance. |
