THE ALPIXP: flora of COLORADO 



T. D. A. COCKERELL 



In 1881 {Bull U. S. Geol. and Geogr. Surv. W., 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 in- 

 -creased, 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 con- 

 clusions. 



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 state- 

 ment 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 tlie upper limit of trees. This may be roughly placed at an 

 altitude of 12,r>()() feet, but it differs according to the character of 

 the exposure as well as the latitude, and may actually descend <'()n- 

 siderably lower. In order to omit nothing, I listed all the |)lauTs 

 given by Rydberg as growing at 12,000 feet or above: 3S(l 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. 



Old World Species 

 Forty-eight species (probably more!) extend to the Old World, 

 861 



