Draba cusickii

B. L. Robinson ex O. E. Schulz

in H. G. A. Engler, Pflanzenr. 89[IV,105]: 105. 1927.

Endemic
Synonyms: Draba sphaeroides var. cusickii (B. L. Robinson ex O. E. Schulz) C. L. Hitchcock
Treatment appears in FNA Volume 7. Treatment on page 304. Mentioned on page 284, 305, 329, 342.

Perennials; (loosely cespitose); caudex branched (with few, persistent leaf remains); scapose. Stems unbranched, 0.3–1.2 dm, pubescent throughout, trichomes (2–)4-rayed, 0.05–0.5(–0.6) mm. Basal leaves rosulate; shortly petiolate; petiole base ciliate (margin not ciliate, trichomes 2-rayed, 0.3–0.6 mm); blade oblanceolate to obovate, 0.4–1.2 cm × 2–5 mm, margins entire or, rarely, denticulate, surfaces pubescent with stalked, (2–)4-rayed trichomes, 0.15–0.4 mm. Cauline leaves 0. Racemes 10–20(–25)-flowered, ebracteate, considerably elongated in fruit; rachis not flexuous, pubescent as stems proximally. Fruiting pedicels divaricate-ascending, straight (not expanded basally), 4–9 mm, pubescent, trichomes (2–)4-rayed, (0.05–0.25 mm). Flowers: sepals broadly ovate, 2–2.5 mm, pubescent, (trichomes short-stalked, 3- or 4-rayed); petals yellow, obovate to oblanceolate, 3.7–6 × 1.5–2.5 mm; anthers ovate, 0.5–0.6 mm. Fruits lanceolate to broadly ovate, plane, flattened, 6–9 × 2–4.5 mm; valves pubescent, trichomes short-stalked, (2–)4-rayed, 0.05–0.25 mm; ovules 10–18 per ovary; style 0.4 0.8(–1) mm. Seeds oblong, 1.2–1.5 × 0.7–0.8 mm. 2n = 26.


Phenology: Flowering Jun–Jul.
Habitat: Basaltic outcrops, talus, rocky soil
Elevation: 2000-2700 m

Discussion

Draba cusickii was divided by R. C. Rollins (1993) into two varieties with significantly different morphologies and chromosome numbers. The Nevada endemic var. pedicellata (2n = 20) is here treated as a distinct species following M. D. Windham (2004). Draba cusickii has the same chromosome number as D. sobolifera but is readily distinguished from that species by having 4-rayed (versus simple or 2-rayed) fruit trichomes. Draba cusickii is known from Steens Mountain (Harney County).

Selected References

None.

Lower Taxa

None.