Description
Rapid-growing, glabrous annual with angular or roundish hollow stems covered with a waxy bloom. In leafy types, leaves consist of one or more pairs of opposite leaflets borne on petioles together with several pairs of tendrils (which are essentially modified leaves) and a single or compound terminal tendril. Leaflets broad and ovate with distinct ribs, and slightly toothed or entire. The two (pseudo) stipules at the base of the leaf are also ovate but much larger than the leaflets. In semi-leafless types the leaflets are replaced by tendrils but the stipules are still present while in leafless types the leaflets are also replaced by tendrils but the stipules are stunted. The two leafless types have better standing ability than the leafy types. The plants are tap-rooted, l m or more in depth, with numerous lateral roots. On each plant, inflorescences comprising one or two self-fertile flowers are borne on the end of axillary peduncles. Flower colour differs according to cultivar with white, pink, lavender, blue and purple represented. Pods containing several seeds, flattened when young but becoming roundish later, are dehiscent along two sides. Seeds range in colour from dun to brown and may be mottled.