Parr 3, 1916] CARDUACEAE: ANTHEMIDEAE 219 
1. ACHILLEA (Vaillant) L. Sp. Pl. 896. 1753. 
Millefolium (Tourn.) Adans. Fam. Pl. 2: 128. 1763. 
Piarmica (Tourn.) Neck. Elem. 1: 14. 1790. 
Alitubus Dulac, Fl. Hautes-Pyr. 499. 1867. 
Perennial caulescent, usually villous, herbs. Leaves alternate, from serrate to tri-pinnat- 
ifid. Heads several or many in corymbs or corymbiform panicles, usually radiate. In- 
volucre campanulate to hemispheric; bracts imbricate in 3-4 series, the outer usually much 
shorter. Receptacle conic or convex, chaffy; paleae membranous, in ours oblong and acute 
or acutish and nearly equaling the disk-flowers. Ray-flowers few, 5-12, pistillate and fertile; 
ligules short and broad, in most species white or sometimes pink or purple, in a few yellow. 
Disk-flowers 15-75, hermaphrodite and fertile; corollas yellowish-white or straw-colored, 
rarely bright-yellow, equaling or slightly longer than the narrowly funnelform throat; lobes 5. 
Anthers with ovate obtuse tips. Style slightly exserted or included; branches in the pistillate 
flowers oblong, obtuse, in the hermaphrodite ones with truncate, fimbriate tips. Achenes 
oblong or obovate, obcompressed, callous-margined, glabrous. Pappus wanting. 
Type species, Achillea santolina L. 
Leaves pinnatifid to tripinnatifid. 
Ligules yellow. 1. A. tomentosa. 
Ligules white, pink, or purplish. 
Rachis of the leaves not dentate. 
Bracts with dark-brown, almost black margins. 
Involucre 5—6 mm. high, 4-5 mm. broad. 
Ultimate seéfments of the leaves long and linear, not 
thickened at the apex; bracts all acute. 2. A. borealis. 
Ultimate segments of the leaves ovate, lanceolate, or 
oblanceolate, short, often thickened at the apex; 
bracts except the outermost obtuse. 
Leaves and stem sparingly villous. 
Upper leaves 1-2 cm. broad, with spreading not 
densely crowded divisions. 
Plant low, 2-4 dm. high; bracts and branches 
of the inflorescence densely villous; ligules 
about 3 mm. long. 3. A. nigrescens. 
Plant tall, 3-6 dm. high; bracts nearly glabrous; 
branches of the inflorescence sparingly pubes- 
cent and glandular; ligules about 4 mm. long. 4. A. Palmeri. 
Upper leaves 5-10 mm. broad, with short densely 
crowded divisions. 5. A. fusca. 
Leaves and stem densely long-villous, almost white. 6. A. arenicola. 
Involucre 3.5-4 mm. high, about 3 mm. broad. 7. A. subalpina. 
Bracts with light-brown, yellowish, or straw-colored margins. 
Involucre 5—8 mm. high, 4 mm. broad or more. 
Plant glabrous or sparingly pubescent; inflorescence open; 
involucre about 8 mm. high; ligules 5 mm. long. 8. A. laxiflora. 
Plant long-villous; inflorescence dense; involucre cam- 
panulate, 5-6 mm. high; ligules 4 mm. long or less. 
Ligules 3-4 mm. long. 
Stem very stout, densely villous; heads and leaf- 
segments densely crowded. 6. A. arenicola. 
Stem more slender, not densely villous; heads not 
densely crowded. 
Ultimate divisions of the leaves linear, not 
thickened, spreading, not crowded; bracts 
with light-brown margins. 9. A. californica. 
Ultimate divisions lanceolate or ovate, usually 
thickened towards the apex, ascending and 
crowded; bracts and their margins of the same 
color, light-yellowish or straw-colored. 10. A. pacifica. 
Ligules 1-1.5 mm. long. 1l. A. gigantea. 
Involucre 44.5, rarely 5 mm. high, 2.5-4 mm. broad. 
Plant puberulent, not villous. 12. A. puberula. 
Plant more or less villous. 
Ultimate leaf-segments linear; rachis merely margined. 
Ligules 2.5-4 mm. long; leaf-segments ascending, ¢ 
crowded. 13. A. lanulosa. 
Ligules 1.5-2.5 mm. long; leaf-segments more or 
less spreading, not crowded. 
Margins of the bracts light-brown, darker than 
the body of the bracts; ligules fully 2 mm. 
long. 14. A. Pecten-Veneris. 
Margins of the bracts of the same color as the 
bracts, yellowish or straw-colored. 
