Foleyola billotii Maire

Shrub or subshrub, deciduous, hermaphrodite, up to 2 m in height, generally very ramose from the base. Stems and older, thicker branches with greyish-brown bark, slightly fissured longitudinally. Branchlets slightly or not spinescent in ± humid soils (as in the Drâa Valley) or spinescent in arid areas; younger branchlets glaucous, reddish —usually purplish—, glabrous. Leaves (1-5 cm in length) alternate; the lower leaves oblong, first purpurescent, then glaucescent, subsessile; the upper leaves from lanceolate to linear, glaucous, sessile. All leaves with entire margin or briefly dentate margin (sometimes the lower leaves), glabrous. Inflorescences in long racemes, very sparse and elongated (1 flower for every few centimetres). Calyx with 4 sepals 6-8mm in length, the 2 outer sepals linear, the 2 inner sepals oblong, obtuse, green-yellowish at first, then purpurescent. Corolla with 4 petals (13-17 mm), oblong, unguiculate, purple-violet. Stamens 6. Fruit a cylindrical-conical silique, 15-30 × 2.5-3 mm. Seeds ellipsoid, brown, with almost smooth surface.