Rough-hairy, stems simple or little branched, 1—3 feet high. Leaves firm, densely and finely hairy, the lower basal ones petioled, oblong or spatulate, laciniate-pinnatifid or entire, mostly obtuse, 2—5 inches long; upper leaves sessile, lanceolate or oblong, entire or dentate, rarely pinnatifid. Heads 1½-4 inches broad, long peduncled; bracts of the involucre spreading, lanceolate, acuminate, rough-hairy, rays 10—18, bright yellow, wedge-shaped, deeply 3-lobed; disc reddish-purple. One of the most showy of the midsummer plants, in the lower valleys of the Rockies, in dry ground and on slopes, especially in the Bow Valley at Banff and in the open country around Golden. [Sidenote: =Arnica cordifolia= Hook. _Heart-leaved Arnica._] Somewhat hairy, stem simple or sparingly branched, 1—2 feet high. Leaves hairy, the basal ovate or orbicular, obtuse or acute, deeply cordate at the base, dentate, 1—3 inches long with slender sometimes margined petioles; stem leaves in 1—3 pairs, ovate or oblong, sessile or short-petioled, much smaller. Heads 1—8, 2—3 inches broad, bracts of the involucre, acute or acuminate, ½—¾ of an inch long; rays 12—16, deep yellow, an inch or more long, toothed at the apex; pappus white. In woods and thickets at the lower altitudes throughout the Rockies; flowering in June. [Sidenote: =Arnica gracilis= Rydb. _Slender Arnica._] Smooth, slender and branched, 6—12 inches high. Leaves with short glandular hairs on both surfaces or smooth, the basal broadly ovate, petioled, dentate, 3-ribbed; stem-leaves about 2 pairs, similar, the upper sessile. Heads several on slender glandular peduncles, disc ½ an inch or less high; involucral bracts, 12—15, lanceolate, acuminate, glandular-hairy as are also the seeds; pappus white; rays about ¾ of an inch long, narrow, bright yellow with a single notch at the apex. On alpine slopes throughout the Rockies; flowering in July, not common. [Illustration: _a_ Arnica cordifolia Hook. Heart-Leaved Arnica. _b_ Arnica louiseana Farr. Pale-Flowered Arnica. (⅗ Nat.)] [Sidenote: =Arnica latifolia= Bong. _Broad-leaved Arnica._] Minutely hairy or nearly smooth, simple or branched. Leaves thin, nearly smooth, or with long scattered hairs; the lower cordate; stem leaves in 2—3 pairs, equal, ovate or oval, sharply dentate, closely sessile by the broad base, or the lowest with contracted bases. Heads ¾ of an inch high on long, slender, hairy peduncles; involucral bracts ½ an inch or more long; oblong-lanceolate, acuminate, with scattered hairs, rays yellow, ¾ of an inch long, with 2 notches at the apex; achenes nearly smooth; pappus white. Throughout the region in woods and open ground usually at an elevation of 5000 to 7000 feet; flowering during July. [Sidenote: =Arnica Chamissonis= Less. _Chamisso’s Arnica._]