92. Draba reptans (Lamarck) Fernald, Rhodora. 36: 368. 1934.
Arabis reptans Lamarck in J. Lamarck et al., Encycl. 1: 222. 1783; Draba caroliniana Walter; D. caroliniana var. dolichocarpa O. E. Schulz; D. caroliniana var. hunteri Payson & H. St. John; D. caroliniana var. micrantha (Nuttall) A. Gray; D. caroliniana subsp. stellifera (O. E. Schulz) Payson & H. St. John; D. caroliniana var. umbellata Torrey & A. Gray; D. coloradensis Rydberg; D. hispidula Michaux; D. micrantha Nuttall; D. reptans var. micrantha (Nuttall) Fernald; D. reptans subsp. stellifera (O. E. Schulz) Abrams; D. reptans var. stellifera (O. E. Schulz) C. L. Hitchcock; D. umbellata Muhlenberg; Tomostima caroliniana (Walter) Rafinesque; T. hispidula (Michaux) Rafinesque; T. micrantha (Nuttall) Lunell
Annuals; scapose or subscapose. Stems (simple or few from, or distal to, base), unbranched, (0.1-)0.3-1.2 (-1.6) dm, sparsely to densely pubescent proximally, trichomes 2 (or 3)-rayed, 0.1-0.6 mm, sometimes with simple or spurred ones, to 0.9 mm, distally usually glabrous, rarely with few trichomes. Basal leaves not rosulate; petiole obscure; blade elliptic or spatulate to obovate or suborbicular, 0.5-2.3(-3) cm × 1.5-8(-13) mm, margins entire, surfaces pubescent abaxially with stalked, 2-4-rayed trichomes, 0.1-0.5 mm, adaxially with simple trichomes, 0.6-1 mm, with stalked, 2-rayed ones, to 0.7 mm. Cauline leaves usually 0, rarely 1-3; sessile; blade similar to basal. Racemes (3-)5-12(-16)-flowered, ebracteate, (subumbellate), not elongated in fruit; rachis not flexuous, usually glabrous, rarely sparsely pubescent. Fruiting pedicels horizontal to divaricate-ascending, straight, (1-)2-7(-9) mm, glabrous or glabrate. Flowers: (late-season ones cleistogamous, apetalous); sepals oblong, 1.5-2.3 mm, pubescent, (trichomes simple); petals (rarely absent), white, spatulate, 2-4.5 × 1-1.5 mm; anthers ovate, 0.4-0.5 mm. Fruits linear to linear-oblong, plane, flattened, (5-)7-16(-20) × 1.2-2.3 mm; valves glabrous or pubescent, trichomes usually simple and antrorse, 0.1-0.3 mm, rarely with fewer, spurred or 2-rayed ones; ovules 32-88 per ovary; style 0.02-0.1 mm. Seeds oblong to ovoid, 0.5-0.8 × 0.3-0.5 mm. 2n = 16, 30, 32.
Flowering Feb-Jun(-Aug). Rock outcrops, dry slopes and hillsides, prairies, glades, roadsides, disturbed sites; 0-3000 m; Alta., B.C., Man., Ont., Sask.; Ala., Ariz., Ark., Calif., Colo., Ga., Idaho, Ill., Iowa, Kans., Mass., Mich., Minn., Mo., Mont., Nebr., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., S.C., S.Dak., Tenn., Tex., Utah, Wash., Wis., Wyo.
Draba reptans is often confused with D. cuneifolia, but the two are easily separated. The rachises and pedicels of D. reptans are usually glabrous (rarely with a few isolated trichomes); those of D. cuneifolia are always densely pubescent. Interestingly, both species show parallel variations in chromosome number; it is currently unclear whether this variation is real or the result of misidentified specimens and/or erroneous counts.