The Alpine Flora of Colorado

Abstract

IN 1881 (Bull. U. S. Geol. and Geogr. Sunv. Terr., vol. 6, no. 1) Gray and Hooker gave a list of the alpine plants of the Rocky Mountains: 184 species, of which 102 extended to the arctic or subarctic regions. Since that time, our knowledge has greatly increased, but the records have been scattered in many publications, and no summary has been available. The appearance of a new Flora of Colorado, written by Dr. P. A. Rydberg and issued by the Colorado Agricultural Experiment Station (Bulletin 100, 1906) makes it possible to gather together the known facts, so far as they relate to that State, and derive from them some general conclusions. It is not pretended, of course, that the information given by Rydberg is complete; and it must doubtless be admitted that some of the recently described species probably do not deserve that rank; but allowing for these and other elements of doubt and difficulty, we may still recognize many broad facts which are not likely to be overthrown. With regard to the details, each statement may be regarded as a challenge to Colorado botanists, to refute it if they can, and in this way even error may be made the cause of progress. The Arctic-Alpine Zone begins at timber line, or the upper limit of trees. This may be roughly placed at an altitude of 12,500 feet, but it differs according to the character of the exposure as well as the latitude, and may actually descend considerably lower. In order to omit nothing, I listed all the plants given by Rydberg as growing at 12,000 feet or above: 386 species. Of these, 202 are not recorded as going above 12,500 feet, and may therefore not pass beyond the Hudsonian Zone; 92 of the 386 descend to below 8000 feet, and of these, 62 do not go above 12,500 feet.