The investigation reported below involves experimental work dealing with the occurrence and type of seed dormancy exhibited by a number of plants collected at high altitudes in Colorado. The objectives of the work include contributing to an understanding of the autecology of the species studied, as well as aiding in an evaluation of the ecological significance of seed dormancy itself. Collections were made during July and August of 1953 at two localities in Colorado: The Rocky Mountain Biological Laboratory north of Gunnison in the Elk Mountains of south-central Colorado (Gunnison County); and near the former University of Colorado Science Lodge, now the Arctic-Alpine Institute, west of Boulder in the Front Range of Colorado (Boulder County). These localities will be referred to below as R.M.B.L. and Alpine Institute, respectively. The altitudes at which collections were made ranged within what is usually considered to be climatically "subalpine" in Colorado, the lowest collection being at 9200 feet and the highest at 10,000 feet elevation.