Annual. Stem decumbent to erect, not rooting at the nodes, square in outline. Leaves sessile, opposite-decussate, pale green, 10-16 x 7-12 mm, ovate-oblong, obtuse or subacute, upper ones smaller, nerves faint, gland dotted (dots reddish), margin minutely papillose. Flowers solitary axillary, red or blue (or shades of them); pedicel 1.4-2.5 (-3.5) cm long, slender, glandulose (hairs with reddish heads), nodding in bud condition, usually exceeding the subtending leaf. Calyx shortly campanulate; lobes 3.5-4 mm long, ovate-lanceolate, subacuminate, midrid pro¬minent, margin membranous and minutely ciliolate. Corolla rotate; lobes 4-5 mm long, obovate, apex erose-denticulate, glandular-stipitate; the glands 3-celled, with the terminal cell globose. Stamens ± equalling the carpel; filaments 2-2.5 mm long, reddish-pink, basally dilated and connate; glandular, the glands 7-11-celled, pinkish, towards base colourless; anthers 1 mm long, basifixed, yellow, ± apiculate. Ovary globose, less than 1 mm broad; style 2-2.2 mm long, pinkish, persistent. Stigma capitate. Pyxidium globose, 4-5 mm broad. Seeds trigonal, c. 1 mm broad, dark brown, vesiculose.