Description from Flora of China
Alloceratium J. D. Hooker & Thomson; Orthorrhiza Stapf.
Herbs annual. Trichomes eglandular, simple, mixed with glandular ones. Stems erect, simple basally, often branched above. Basal leaves petiolate, not rosulate, sinuate-dentate, dentate, or rarely pinnatisect. Cauline leaves similar to basal ones, uppermost entire, subsessile. Racemes few flowered, ebracteate, elongated in fruit. Fruiting pedicels thickened, ascending or subdivaricate. Sepals oblong-linear, connivent, erect, base of lateral pair saccate. Petals purple or whitish, longer than sepals; blade linear-oblanceolate, apex obtuse; claw obscurely differentiated from blade. Stamens 6, erect, tetradynamous; filaments not dilated at base; anthers ovate, obtuse at apex. Nectar glands 4, lateral, 1 on each side of lateral stamen; median glands absent. Ovules 10-40 per ovary. Fruit dimorphic siliques, linear, sessile, torulose, glabrous; lowermost fruit indehiscent, terete, corky, breaking into 1-seeded units; upper fruit dehiscent, latiseptate, with obscurely veined leathery valves; replum rounded; septum corky in lower fruit, opaque, complete, and veinless in upper ones; style to 8 mm, stout, cylindric or subconical; stigma capitate, 2-lobed, lobes connivent. Seeds uniseriate, broadly winged, oblong or orbicular, strongly flattened; seed coat smooth, not mucilaginous when wetted; cotyledons accumbent.
One species: C and SW Asia, SE Europe.