Pacific Yarrow

Achillea pacifica Rj^dberg, sp. nov
A stout perennial, with a creeping rootstock; stem 3-7 dm. high, sulcate, usually decidedly long-villous, simple or branched above; leaves 1-2 dm. long, 5-10 mm. wide, linear in outhne. villous, bipinnatifid; primary divisions ovate in outline, short, ascending, rather crowded, the ultimate ones lanceolate or ovate, strongly punctate, callous-thickened towards the spinulosemucronate tips; heads numerous, in roundtopped corymbiform panicles; involucre about 5 mm. high and 4 mm. broad, 11ous, campanulate; bracts about 20, yellowish or strawcolored, with margins of the same color, the outer ones ovate, the inner elliptic or oblong, all obtuse or rounded at the apex; ray-flowers about 5; ligules suborbicular, round-lobed, 3-4 mm. long; disk-flowers 20 or more; corollas j-ellowish-white, nearly 3 mm. long; achenes fully 2 mm. long, thick-margined.
Type collected at Grenada, Siskiyou County, California, June 19, 1905, A. A. Heller S067 (herb. N. Y. Bot. Card.).
Distribution: Washington and Idaho to southern California.