Arnica sulcata

Arnica sulcata Rydberg, sp. nov
Rootstock short, branched; stem about 1.5 dm. high, strongly sulcate, glandular-puberulent and somewhat villous; basal leaves oblanceolate, strongly 5-ribbed, 1-4 cm. long, villous and glandular-puberulent, entire-margined; stem-leaves 1 or 2 pairs, linear-lanceolate, sessile, 1-4 cm. long, acute; heads 1 or 2; peduncles 2-7 cm. long; involucre turbinate, 12-15 mm. high, 15-20 mm. broad, glandular-puberulent and slightly villous; bracts about 15, lancelinear, acuminate; ray-flowers 10-15, the ligules orange, 1 cm. long or less, 4 mm. wide, distinctly 3-toothed; achenes 5 mm. long, hirsute; pappus-bristles sordid, 8 mm. long, shortplumose.
Type collected on Scott Mountains, Siskiyou Countv, California, August 22, 1876, E. L. Greene 1005 (.Gray Herbarium).