COMP OS I TAE. 1013 



narrowly linear, sessile, obtusish, 1-5 cm. long, 2 mm. wide or less, often ciliate 

 with a few bristles near the base; heads several or numerous, short-peduncied, 

 about 6 mm. broad; involucre short-cylindric or narrowly campanulate, its bracts 

 about 8, linear, acutish, partly enclosing the outer achenes; rays few, 3-toothed, or 

 entire; pappus a crown of 4-6 somewhat united short scales, with or without 2 

 slender short awns. In dry soil, Neb. and Colo, to Mex. and Ariz. Plant with the 

 odor of lemons. May-Oct. 



84. ACHILLEA L. 



Herbs, mostly perennial, with erect, leafy stems, finely dissected, pinnatifid or 

 serrate alternate leaves, and small heads of both tubular and radiate flowers, corvm- 

 bose at the ends of the stem and branches. Involucre obovoid, or campanulate, its 

 bracts appressed, imbricated in few series, the outer shorter. Receptacle nearly 

 flat, or convex, chaffy, the membranous chaff subtending the disk-flowers. Ray- 

 flowers pistillate, fertile, the rays white or pink. Disk-flowers perfect, fertile, 

 their corollas yellow, 5-lobed. Anthers obtuse and entire at the base. Style- 

 branches of the disk-flowers truncate. Achenes oblong or obovate. slightly com- 

 pressed. Pappus none. [Named for Achilles. ] About 75 species, natives of the 

 northern hemisphere, mostly of the Old World. Besides the following, several 

 others occur in northwestern N. Am. 



Leaves serrate. i. A. Ptarmica. 



Leaves finely dissected. 



Involucre broadly campanulate ; bracts fuscous-margined ; rays 10-20. 



2. A. borealis. 

 Involucre oblong; bracts scarcely fuscous-margined; rays 5-10. 



Rays 3-6 mm. broad ; plant villous ; achenes broadly margined. 



3. A. lanulosa. 



Rays 2-3 mm. broad ; plant sparsely villous or glabrate ; achenes scarcelj mar- 

 gined. 4. A. Millefolium. 



1. Achillea Ptarmica L. SNEEZEWORT. WHITE TANSY. (I. F. f. 3982.) 

 Perennial by horizontal or creeping rootstocks ; stem glabrous, or slightly pubes- 

 cent, nearly or quite simple, 3- 6 dm. high. Leaves linear or linear-lanceolate, ses- 

 sile and slightly clasping at the base, acute at the apex, regularly and closely serrate, 

 sometimes pubescent on the veins beneath, 3-6 cm. long, 3-6 mm. wide; heads not 

 very numerous, 10 18 mm. broad; peduncles puberulent; bracts ovate-oblong, 

 obtuse or obtusish, slightly tomentose; rays 5-15, white, rather large. In moist 

 soil, Newf. to Quebec, Mass, and Mich. Nat. from Europe. July-Sept. 



2. Achillea borealis Bong. NORTHERN YARROW. Perennial, 2-4 dm. 

 high; stem more or less lanate. Leaves bipinnate. with numerous crowded 

 segments, sparingly lanate; corymb dense; heads 4-8 mm. high; involucral bracts 

 somewhat scariouswith broad fuscous margins; rays large, white or pink, 3-5 mm. 

 broad; achenes prominently winged. Lab. to Alaska, south in the mountains of 

 the Pacific Coast to Mex. June-Sept. 



3. Achillea lanulosa Nutt. WESTERN YARROW. Perennial, 3-5 dm. high; 

 stem lanate. Leaves finely bipinnatifid, with approximate segments; cyme rather 

 dense in age. becoming flat-topped; involucral bracts stramineous, with greenish 

 keel and brown margins ; achenes elliptical, broadly margined. Plains and 

 mountains, S. Dak. to Br. Col., south to Mex. and Kans. Also introduced further 

 east. June-Sept. 



4. Achillea Millefolium L. YARROW. MILFOIL. (I. F. f. 3983.) Peren- 

 nial from horizontal rootstocks; flowering stems sparsely pubescent, or nearly gla- 

 brous, simple, or corymbosely branched above, 3-6 dm. high. Basal leaves and 

 those of the numerous short sterile shoots, mostly petioled, sometimes 25 cm. 

 long and I cm. wide, those of the stem sessile, all somewhat pubescent or nearly 

 glabrous; heads numerous, 4-6 mm. broad, in terminal compound dense, some- 

 what convex corymbs; involucre ovoid, its bracts oblong, stramineous with greenish 

 keel, obtusish, pubescent ; rays 4-6, white, or often pink or purple. In various 

 situations in the east occurring as a naturalized weed. Native of Europe and 

 Asia. June-Nov. 



Achillea ligustica All., a native of Europe, has been collected in N. Y. and Mass. 

 It differs from A, Millefolium in the open loose panicle and broad and short leaf-seg- 

 ments. 



