Rayless Arnica

Plants 15–60 cm. Stems mostly simple or distally branched. Leaves 3–7 pairs, sometimes crowded at stem bases (basal leaves often persistent on sterile rosettes); petiolate (petioles narrow, 1.5–8 cm, often broadly winged on distal reduced leaves); blades usually ovate to broadly lanceolate, seldom subcordate, 2–12 × 1–7 cm, margins usually serrate to coarsely dentate or crenate, rarely subentire, faces glabrate to pilose, stipitate-glandular. Heads 3–10(–30; erect). Involucres turbinate-campanulate. Phyllaries 8–15, ovate-lanceolate to narrowly lanceolate. Ray florets usually 0 (corollas of peripheral florets rarely dilated, resembling rays). Disc florets 20–50; corollas yellow; anthers yellow. Cypselae dark gray, 6–8 mm, hirsute (hairs duplex) and stipitate-glandular; pappi white, bristles usually barbellate, sometimes subplumose. 2n = 38, 57, 76.

Arnica alata Rydberg; A. cordifolia Hooker var. eradiata A. Gray; A. discoidea var. alata (Rydberg) Cronquist; A. discoidea var. eradiata (A. Gray) Cronquist; A. parviflora A. Gray

Arnica discoidea Benth. PI. Hartw. 319. 1849
Rootstock short, branched; stem 3-6 dm. high, striate, villous, somewhat glandular in the inflorescence; basal leaves and those of the offsets long-petioled, the petioles 5-10 cm. long, villous; blades ovate, acute or truncate at the base, coarsely dentate, 5-10 cm. long, acute, villous on both sides, somewhat paler beneath; stem-leaves usually 3 pairs, the lowest pair similar to the basal leaves, but the petioles often winged, the second pair ovate, with broadly winged petioles, which are enlarged and clasping at the base, the uppermost pair usually sessile, ovate; heads 3-20, cymose; involucre round-campanulate, 10-12 mm. high, 10-15 mm. broad, viscid-villous; bracts 12-15, linear-oblong, acute; ray-flowers wanting; disk-corollas about 7 mm. long; achenes 5 mm. long, angled, hirsute; pappus-bristles white, 7 mm. long, barbellate.
Type locality: Monterey, California.
Distribution: Wooded hills from south-central California to Oregon and Washington (?), mostly in the coast ranges and the Cascades.

Arnica alata Rydberg, sp. nov
Rootstock short; stem 3-5 dm. high, more or less villous, angled and striate, slightly glandular above; basal leaves and lower stem-leaves long-petioled, the petioles 5-7 cm. long, broadly winged, villous; blades cordate, 5-8 cm. long, 4-6 cm. wide, rather thick, shortvillous on both sides, sharply dentate, acute; upper leaves with ovate blades and very broadly winged petioles, or sessile with entire dilated bases; heads 1-3, rarely 4-6, long-peduncled; involucre rounded-campanulate, 15-18 mm. high, 15-22 mm. thick; bracts oblong, acute, villous; ray-flowers wanting; disk-corollas 10 mm. long; achenes 7 mm. long, sparingly hirsute; pappus-bristles 5 mm. long, white, barbellate.
Type collected in Yosemite, California, 1865, Torrey 258a (herb. N. Y. Bot. Gard. and Columbia Univ.).
Distribution : Mariposa and Tuolumne counties, California.

Arnica parviflora A. Cray, Proc. Am. Acad. 7: 363. 1868
Rootstock horizontal; stem 2-5 dm. high, finely short-pubescent, somewhat glandular on the upper part, often tinged with red; basal leaves and those of the offsets long-petioled, the petioles 3-7 cm. long; blades cordate or ovate, 3-5 cm. long, coarsely dentate-, with broad mucronatc-tipped teeth, finely short pubescent on both sides, paler beneath, more or less 3-5-riblicd ; stem-leaves mostly 3 pairs, thl low. i pair similar to the basal ours, the Diddle ones with shorter and often Kinged petioles, the upp. rnW Her, tinleaves of the
inflor nail, ovate or lanceolate, dental or entire; beads 3 11; involucre turbin
about 1 cm. high and broad, villous and lomewhat glandular; bracts 10 12, oblong-lanceol
acute; ray-flowers (ranting; disk corollas 7 mm. long; acheni < mm. Ion,;, angled, striate, glandular-granuliferous; pappUl bristli white, 6 mm long, short plumose.
Tvch locality: llnmbolfli County, California
.Mm noM Northern California .mil southern Oregon.

Arnica grayi A. Heller, Muhlenbergia 1: 5. 1900
Arnica cordifolia eradiata A. Gray, Syn. Fl. N. Am. I 2 : 381. 1884. Arnica falconaria Greene, Ottawa Nat. 23: 215. 1910.
Rootstock horizontal; stem 3-6 dm. high, sulcate, long-villous, slightly viscid above; basal leaves and those of the offsets long-petioled; petioles 3-8 cm. long, villous; blades ovate or subcordate, 4-10 cm. long, coarsely dentate, acute, villous on both sides, 3-5-ribbed; stemleaves 2 or 3 pairs, the lowest pair similar to the basal ones, the upper sessile with an enlarged base, ovate, about 5 cm. long, those of the inflorescence ovate, reduced; heads 1-7, cymose; involucre rounded-campanulate, 10-13 mm. high, 10-15 mm. broad; bracts about 10, ovate, acute; ray-flowers wanting; disk-corollas 7-9 mm. long; achenes 6 mm. long, angled, hirsute; pappus-bristles white, 10 mm. long, barbellate.
Type locality: Eastern Oregon.
Distribution: Open woods, Washington to California.

Arnica discoidea is a North American species of arnica in the sunflower family. It is known by the common name rayless arnica because its flower heads have disc florets but none of the showier ray florets. It is native to the woodlands, forests, and chaparral of the western United States (Washington, Oregon, California, and western Nevada (Washoe County).

Arnica discoidea is a rhizomatous perennial herb producing a hairy, glandular stem 20 to 60 centimeters tall. There are several pairs of toothed oval to spade-shaped leaves on long petioles around the lower half of the stem. The inflorescence contains a few to many flower heads which are coated with glandular hairs. Each head contains only disc florets, but some of the florets around the edge can be expanded and resemble ray florets, making identification of the plant by its floral characteristics rather difficult.

The fruit is an achene about 7 millimeters long, not counting its light-colored pappus.