Perennial, with oval or fusiform tubers. Flowers chasmogamous and cleistogamous, the former terminal or in the axils of upper leaves, the latter in the axils of lower leaves. Calyx 5(-4), basally united. Petals 5(-4), absent in cleistogamous flowers. Stamens 10, 2 in cleistogamous flowers). Styles 2-3, filiform (in cleistogamous flowers styles 2, short and united). Ovary 1-locular, dehiscing by 4 valves. Seeds globose-reniform, tuberculate.