105. Draba sphaerocarpa J. F. Macbride & Payson, Amer. J. Bot. 4: 266. 1917.
Draba argyrea Rydberg var. sphaerocarpa (J. F. Macbride & Payson) O. E. Schulz
Perennials; caudex branched (branches loose or compact, sometimes terminating in sterile rosettes); scapose. Stems unbranched, (0.15-)0.3-0.8 (-1.1) dm, usually densely pubescent throughout, trichomes stalked, 2-5-rayed, 0.1-0.4 mm, with subsessile, smaller, 4-8-rayed ones, rarely proximally with some simple trichomes. Basal leaves rosulate; subsessile; petiole margin not ciliate; blade oblanceolate to obovate or linear-oblanceolate, (0.2-)0.3-0.9(-1.5) cm × 1-2.5(-4) mm, margins entire, (not ciliate), surfaces canescent with short-stalked, 8-15-rayed, stellate trichomes, 0.1-0.25 mm. Cauline leaves 0. Racemes (4-)6-18(-23)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. Fruiting pedicels divaricate-ascending to ascending, straight, 4-9(-13) mm, pubescent as stem. Flowers: sepals oblong, 2-3.5 mm, pubescent, (trichomes 4-6-rayed); petals yellow or lemon, oblanceolate to spatulate, 4-6 × 1.5-3 mm; anthers ovate, 0.4-0.6 mm. Fruits ellipsoid to ovoid, plane, inflated at least basally, 2-5(-6) × 1.5-2.5(-3.5) mm; valves pubescent, trichomes 2-4-rayed, 0.03-0.2 mm (some or all rays spurred); ovules 4-10 (-12) per ovary; style 0.2-0.9(-1.2) mm. Seeds ovoid, 1-1.6 × 0.7-1.2 mm. 2n = 20.
Flowering May-Jul. Granite outcrops and rocky slopes in open pine forests; 2100-2800 m; Idaho.
Draba sphaerocarpa is a distinctive species known only from Boise, Custer, Idaho, and Valley counties in central Idaho.