TORREYA 



September, 1918 

 Vol.|8 No. 73 



NOTES ON THE FLORA OF BOULDER. COUNTY, COLO- 

 RADO 



By T. D. a. Cockerell 



The Flora of Boulder County has been recorded in a volume of 

 311 pages by Professor F. P. Daniels (Univ. of Missouri Studies, 

 science series, vol. II, no. 2, 191 1), who catalogues 486 genera and 

 1 ,225 species. Since the publication of this work about 27 genera 

 and 76 species have been added, principally from the observa- 

 tions of Messrs. D. M. Andrews and E. Bethel. A few species 

 have been deleted, but in round numbers the Boulder County 

 list includes 1,300 species of flowering plants and pteridophytes. 

 Comparing this with an area of similar size in Switzerland, we 

 find a striking correspondence: 



Boulder County. Area 751 square miles. 1,300 species. 

 Canton of St Gallen. Area 779 square miles. 1,295 species. 



The Rocky Mountains are much more ancient than the Swiss 

 alps, but this fact appears to have little or no influence on the 

 composition of the present flora. The Swiss alps are heavily 

 glaciated, while the Rocky mountains of Colorado are almost 

 entirely bare; the mountains of Switzerland are also much more 

 closely grazed than ours, and the lowlands are more extensively 

 and intensively cultivated. These differences would lead us to 

 expect a larger flora in a corresponding area in Colorado than in 

 Switzerland. 



In 1906 Rydberg recognized 2,912 species of seed plants and 

 pteridophytes for the whole of Colorado ; while in 1909 Schinz and 

 Keller listed 2,460 for Switzerland, the area of which is of course 

 much less. 



The genera added to the Boulder County list are the fol- 



[No. 8, Vol. 18 of TORREYA, Comprising pp. 157-176, was issued 7 September, 1918] 



177 



