Achillea palmeri

Achillea palmeri Rydberg, sp. nov
A stout perennial, with a creeping rootstock ; stem 3-6 dm. high, sulcate, sparingly villous, branched above; leaves usually less than 1 dm. long, 1-2 cm. wide, bipinnatifid, sparingly villous; primary divisions ovate, spreading, the ultimate ones lanceolate, rather conspicuously punctate, callous-thickened towards the spinulose-mucronate tips; heads numerous, in broad, branched, cor>-mbiform, rather flat-topped panicles; involucre broadly campanulate, fully 5 mm. high and about as broad, nearly glabrous; bracts about 20, the outer ovate and acutish, the inner elliptic and obtuse; margins narrow, dark-brown; ray-flowers usually 5; ligules suborbicular, about 4 mm. long, white; disk-flowers about 25; corollas fully 3 mm. long, yellowishwhite; achenes more than 2 mm. long, thick-margined.
Type collected at Saltillo, Coahuila, or vicinity, November 10-20, 1902, Edward Palmer 326 (herb. N. Y. Bot. Gard.).
DisTRiBUTio.v: Coahuila to Vera Cruz and Hidalgo; apparently also southwestern Colorado, southeastern Utah, and central California.