458 Rvdberg : Rocky Mountain flora 



mm. broad, the less numerous rays, and the short and crowded 

 leaf-segments. It belongs to the higher Rocky Mountains. 



Achillea borealis Bong. Veget. Sitcha 149. 1832 



In many respects this is close to the typical Achillea Mille- 

 folium. The heads are usually larger and have more rays; the 

 bracts are usually darker but not always so. The main differences 

 are in the inner bracts, which are decidedly acute, the narrow 

 and usually long segments of the leaves, the rachis, which is 

 almost without a wing margin, and the longer pubescence. The 

 leaves resemble much those of A. occidentalis and A. calif ornica. 

 The range of A. borealis extends from the Mackenzie to Alberta, 

 British Columbia, and Alaska. The plant of Newfoundland and 

 Labrador, which has been referred to this species is somewhat 

 different. So far as I know, it has not received any specific name, 

 but it has been described under the following name: 



Achillea Millefolium nigrescens E. Meyer, PI. Labrad. 



65. 1830 



It has the large heads and dark-margined bracts of A. borealis, 

 but the bracts are not acute, the leaf-segments are broad and 

 short, and the rachis has a decided wing-margin. It agrees there- 

 fore in every respect with A. Millefolium, except the larger head 

 and the more numerous flowers. 



Achillea californica Pollard, Bull. Torrey Club 26: 369. 



1899 



This, so far as I know, is not found in the Rocky Mountain 

 region. It is restricted to the Pacific Coast. It is usually taller 

 and more robust than any of the species mentioned above. The 

 character of the head is practically the same as in A. Millefolium, 

 but the heads are larger, about as large as in A. borealis. The 

 margins of the bracts are usually not so dark as in that species 

 and none of the bracts are acute. The leaf-form is more that of 

 A. borealis and A. occidentalis, but the segments are usually still 

 more elongated and more divaricate. The leaves are usually 

 thrice rather than twice pinnatiiid. 



