are ascribed to Rydberg; it is of course vinderstood that this 

 ascription does not imply that these plants were collected by 

 Rydberg in the localities named, but merely that by examina- 

 tion of the plants or otherwise he is satisfied that they occur 

 in those places. In the case of plants collected by myself I 

 have added the collection number, so that these can be identi- 

 fied at any time. I may add that besides the set of Boulder 

 plants in the Herbarium of the University of Missouri, there 

 is a duplicate set in the Herbarium of the Michigan Agricul- 

 tural College; there is also a set in my own possession. The 

 Herbarium of the Missouri Botanical Garden has an incom- 

 plete set. As the numbers are the same for all plants of the 

 same species, the identification of any of these plants can be 

 made out from the number given in the list. 



In the introduction I have sought to present what knowl- 

 edge I have of the distribution of plants in Boulder County. 

 I have tried to present them in their natural plant-societies. 

 I saw, however, too little of the montane, subalpine, and the 

 alpine floras to be able to give a comprehensive account of these, 

 and it must be remembered that I did not see the vernal facies 

 of any portion of the vegetation. 



As to nomenclature I have followed, except where plainly 

 deficient in the light of later investigation, that of Rydberg's 

 Flora of Colorado. While I feel that in the case of both 

 genera and species there has been an over-multiplication — as 

 for instance the splitting up of such a natural group as the 

 pines into several genera, yet at the time of the preparation 

 of this Flora the only convenient guide was Rydberg's work. 



It is to Professor T. D. A. Cockerell of the University of 

 Colorado to whom I am most indebted for assistance in this 

 work. Remote both from the vegetation itself and from an 



