Nemesia williamsonii K.E.Steiner

Annual herb up to 280 mm tall; stems angular in cross section with 4 or 5 sides, up to 2.5 mm wide, corners ridged, glandular pubescent. Leaves simple, opposite, mostly sessile, lance-ovate to ovate. 10-43 x 5-20 mm, sparsely glandular puberulous to nearly glabrous, base rounded to cuneate, apex acute, margins entire to toothed; petioles up to 8 mm long, glandular pilose. Flowers axillary or in lax, terminal racemes, racemes up to 150 mm long; bracts alternate, sessile, lanceolate, lowermost leaf-like, uppermost reduced to ±3.6 x 1 mm, base truncate, apex acute, margins entire; pedicels ±5-14 mm long, glandular pubescent. Calyx 5-lobed, central upper lobe ±3.5-4.1 x 0.95-1.00 mm, lateral upper lobes ±3.3-3.6 x 0.8-1.1 mm, lower two lobes ±2.8-3.3 x 1-0-1.3 mm, all lobes lanceolate, acute, sparsely glandular pilose. Corolla bilabiate, 10.1-16.1 x 9.6-14.6 mm, upper lip four-lobed, two inner (upper) lobes oblong to obovate, 2.7-5.1 x 2.8-3.8 mm, base strongly oblique, apex rounded to emarginate, two outer (lateral) lobes oblong, 3.1-5.1 x 3.2-4.1 mm, base strongly oblique, apex rounded to emarginate; upper lip orange (rarely yellow, see Thompson & Le Roux 364) except for a bright yellow patch (2.8 x 2.8 mm) just above corolla opening, pale orange reverse, lower lip oblong to obcordata, 4.9-6.7 x 4.5-5.6 mm, orange (occasionally yellow, see Thompson & Le Roux 364), pale orange reverse, basal portion inflated into a convex projecting palate; palate ±2.9-3.2 x 3.5-4.1 mm, bright yellow, longitudinally grooved, glabrous; hypochile (floor of corolla tube) ±3.1-3.3 mm long, sides invaginated to form a narrow channel, base drawn out into a spur, (2.4-)3.1-4.2(-5.3) mm long, ± straight or curving downward in distal third, orange-white. Stamens four, whitish, lying in a shallow depression in upper surface of corolla tube; filaments of anticous pair (twisted into posticous position) ±2.5 mm long, ± straight, except at base and apex, glabrous or with a few glandular trichomes; posticous filaments ±0.85 mm long, ± straight except at base, sparsely glandular pubescent; anthers 0.5-0.65 mm long, each pair strongly coherent. Ovary oblong-ovate in outline, 1.2-1.3 x 1.0-1.1 mm. laterally compressed; style ±0.75 mm. slightly curved, compressed contrary to the ovary, apex wider than base, lying between anther pairs, stigma a crescent-shaped apical band. Capsules oblong in outline, ±4.5-13.1 x 3.6-6.9 mm, laterally compressed contrary to the septum, apex emarginate to bilobed, lobes rounded to acute. Seeds dimorphic, plants with either winged or wingless seeds; winged seeds widely ovate, ±1.8-2.3 x 1.8-24 mm, brown, verruculate, wing membranous with numerous parallel, brownish veins, wingless seeds oblong, ±1.5-1.8 x 0.8-1.0 mm, brown, verrucate.