22 HOW TO USE THE KEYS 



and distribution in Colorado but is very helpful), the 

 various publications of the United States Department 

 of Agriculture on Agrostology of which American 

 Grasses I, II and III and the monographs of different 

 genera are about the last word on the subjects covered. 

 Coulter's Flora and the United States Department of 

 Agriculture publications may be obtained from the 

 Division of Publications, Washington, D. C, at a 

 nominal cost. Rydberg's Flora is Bulletin No.' 100 of 

 the Colorado Experiment Station. Coulter and Nel- 

 son's Manual is published by the American Book Com- 

 pany and Small's Flora may be had from the author, 

 Dr. J. K. Small, New York Botanical Gardens, Bronx 

 Park, New \"ork City. 



