Rydberg : Rocky Mountain flora 4^7 



Achillea Millefolium. It is characterized by the small rays, 

 only 1.5-2.5 mm. broad, and straw-colored bracts, pointed out 

 by Pollard. It differs also from A. Millefolium in the narrow 

 linear and usually more elongated segments of the leaves. There 

 is also only a trace of a wing-margin on the rachis and the stem 

 is usually more hairy and with longer hairs. DeCandolle regarded 

 it as a variety of A. Millefolium and stated that it is intermediate 

 between that species and A. setacea, a native of Southern Europe. 

 In my opinion it is nearer to A. setacea, having the small rays 

 and narrow segments of that species, but is more hairy. It is the 

 common native form of the prairie region from Wisconsin to Ken- 

 tucky, Arkansas, and eastern Nebraska, but specimens have 

 been collected as far east as Pennsylvania and South Carolina. 

 Three specimens from southern Colorado I have also referred here. 



Achillea lanulosa Nutt. Journ. Acad. Nat. Sci. Philadelphia 7: 



36. 1834 



A. tomentosa Pursh, Fl. Am. Sept. 561. 1814. Not A. tomen- 



tosa L. 1753. 



This resembles the foregoing in many respects; the pubescence 

 (although often more copious) and the color of the bracts are 

 the same. The segments of the leaves are much shorter and more 

 crowded and more directed forward; the rachis has not even a 

 trace of a wing margin and the rays are much larger, 2.5-4 mm. 

 (Pollard gives them up to 6 mm.) broad. This is the common 

 plant of the Rocky Mountain region and its range extends from 

 Saskatchewan to Kansas, New Mexico, northern Mexico, the 

 mountains of California, and British Columbia. 



Achillea subalpina Greene, Leaflets 1: 145. 1905 

 A. lanulosa alpicola Rydb. Mem. N. Y. Bot. Gard. 1: 426. 1900. 

 A. alpicola Rydb. Bull. Torrey Club 33: 157. 1906. 



This resembles a depauperate Achillea lanulosa in habit, but 

 the margins of the bracts are strongly colored, usually almost 

 black, though sometimes only brown, and such specimens ap- 

 proach closely A. lanulosa. The inner bracts as are a rule de- 

 cidedly acute and in this respect it resembles A. borealis. It 

 differs, however, from that species in the small heads, not over 4 



