Description from Flora of China
Herbs annual, biennial, or perennial, rarely subshrubs or shrubs. Trichomes stellate, dendritic, or stalked forked, sometimes mixed with fewer simple ones, rarely primarily simple. Stems simple or branched apically. Basal leaves petiolate, rosulate, simple, often entire, sometimes dentate, rarely lyrate-pinnatifid. Cauline leaves sessile and auriculate, sagittate, or amplexicaul, very rarely petiolate, entire or dentate. Racemes ebracteate or rarely bracteate throughout or only basally, sometimes in panicles, elongated in fruit. Fruiting pedicels erect, ascending, divaricate, or reflexed. Sepals ovate or oblong, base of lateral pair saccate or not, margin membranous. Petals white, pink, or purple; blade spatulate, oblong, or oblanceolate, rarely obovate, apex obtuse or emarginate; claw shorter than sepals. Stamens 6, tetradynamous; filaments usually not dilated at base; anthers ovate, oblong, or linear, obtuse at apex. Nectar glands confluent, subtending bases of all stamens; median glands sometimes toothlike and free, rarely absent; lateral glands semiannular or annular. Ovules 12-110 per ovary. Fruit dehiscent siliques, linear, latiseptate, sessile or rarely shortly stipitate; valves papery, with an obscure or prominent midvein, smooth or torulose; replum rounded; septum complete, membranous, translucent, veinless; style obsolete or distinct; stigma capitate, entire or slightly 2-lobed. Seeds uniseriate or biseriate, winged or margined, oblong or orbicular, flattened; seed coat smooth or minutely reticulate, not mucilaginous when wetted; cotyledons accumbent.
The limits of Arabis are highly artificial, and the genus is defined primarily on the basis of having branched trichomes, flattened, linear fruit, and accumbent cotyledons. However, this combination of characters has evolved independently several times in the Brassicaceae. A critical study of the genus on worldwide basis is much needed.
About 70 species: temperate Asia, Europe, North America; 14 species (one endemic) in China.