3GG Pollard: The Genus Achillea in North America 



sumption that it is not indigenous."^ The theory of range-exten- 

 sion explains this circumstance, but fails to take cognizance of the 

 manifest differences of structure existing between eastern and west- 

 ern individuals, and again between western and northern t}'pes — 



differences too marked to find explanations in ordinary circum- 

 stances. Moreover, very few modern taxonomists would admit 

 that a single species can occur unchanged throughout so vast a 

 territory as Europe, northern Asia and North America, under such 

 varied conditions of soil, temperature and environment. 



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The extensive travels of Nuttall convinced that keen-eyed 

 botanist that the yarrow of the western plateau was not only in- 



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digenous, but specifically distinct from the eastern A, Millefolium. 



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He therefore published it as A. lannlosa^ a name which" was soon 

 thereafter relegated to synonymy by Hooker. Pursh had previ- 

 ously identified as A. tonioitosa of Willdenow a plant collected by 

 Lewis in Oregon, the rays of which were stated to be yellow. • 

 Nuttall cites touioitosa as a synonym, the fact being that Willde- 

 now's name was applied originally by Linnaeus to a species ot 



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south Europe known to possess yellow rays. Pursh's error can 

 accordingly be accounted for on the basis of transposed or mis- 

 taken labels, scarcely, as Dr. Gray suggested, because the rays of 

 his specimen turned yellow in drying, a phenomenon which, as 



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Professor Greene has remarked to me, never occurs in this genus. 



The yarrow found abundantly in Alaska and northern British 



Columbia was described by Bongard as A, borcalis, a name which 



promptly met the same fate as laiuilosa in Hooker's Flora Boreali- 



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■ Americana. The species extends southward to the Cascades and 

 Sierras, penetrating even into Mexico, but it is doubtful if it occurs 

 below an altitude of 8000 feet in the southern half of its range. 

 Another species, growing also at high elevations, is found in 

 Mexico. California furnishes two new species, one of the coast, 

 distinguished by its peculiar foliage, which is harsh and scabous, 

 one from the San Joaquin valley, remarkable for its large stature, 

 branching habit, and small rays. These latter forms are manifestly 

 members of the subgenus j5'//<^7t7////t'rt, and therefore might logically 



^Mi. Gnille, in discussing the use made of the yarrow by the Klamath Indian^; 

 of Oregon, remarks that it is *' from the evidence of its occmrcnce even in veiy remote 

 and unsettled parts of the plains and from the statements of the Indians, un<|uestionably 

 native in our Northwest/' (Contr. U. S. Nat. Herb. 5:105. 1897.) 



