Description from Flora of China
Hymenophysa C. A. Meyer; Physolepidion Schrenk.
Herbs perennial, rhizomatous. Trichomes simple. Stems erect or rarely decumbent, branched above. Basal leaves petiolate, rosulate or not, lyrate, sinuate, dentate, or entire. Cauline leaves sessile, auriculate, sagittate, or amplexicaul at base, margin entire or dentate. Racemes ebracteate, corymbose, grouped in panicles, elongated slightly in fruit. Fruiting pedicels slender, divaricate. Sepals ovate or oblong, deciduous, erect or spreading, base of lateral pair not saccate, margin membranous. Petals white; blade obovate or spatulate, apex obtuse; claw subequaling sepals. Stamens 6, tetradynamous; anthers ovate or oblong, obtuse at apex. Nectar glands confluent and subtending bases of all stamens; median glands present. Ovules 2 per ovary; subapical. Fruit indehiscent silicles, ovoid, obovoid, cordate, obcordate, reniform, or globose, terete or strongly angustiseptate, inflated or not, often sessile; distinctly or obscurely veined, sometimes reticulate, glabrous or pubescent, keeled or not, wingless; replum rounded; septum complete or fenestrate, membranous, translucent, veinless; style distinct, cylindric, exserted from apical notch of fruit; stigma capitate, entire. Seeds wingless, ovoid or ellipsoid, plump; seed coat minutely reticulate, mucilaginous when wetted; cotyledons incumbent.
The genus Cardaria differs from Lepidium in having indehiscent instead of dehiscent fruit and confluent instead of separate nectar glands. However, it is highly questionable if these differences justify the recognition of two independent genera. In fact, recent molecular studies clearly show that the nearest relatives of Cardaria are the L. campestre group. Critical taxonomic studies of the boundaries of these two genera are needed.
Two species: native to the Irano-Turanian and Mediterranean regions, widely naturalized elsewhere; two species in China.