Flat-top mille-graines

Oldenlandia corymbosa, commonly known as flat-top mille-graines or diamond-flower, is a slender annual herb of the family Rubiaceae with a pantropical and pansubtropical distribution, occurring as a common weed of cultivation, lawns and disturbed ground throughout the Indian subcontinent, tropical Asia, Africa, the Americas and Pacific islands. The plant grows 10 to 30 centimetres tall from a fine taproot, with quadrangular, sparsely branched, glabrous or minutely pubescent stems that are erect, ascending or prostrate. The opposite, sessile to subsessile leaves are linear to linear-lanceolate, 10 to 30 millimetres long and 1 to 4 millimetres wide, acute at both ends, with revolute margins and prominent interpetiolar stipules bearing a few short bristles. Tiny white to pale pinkish four-lobed funnel-shaped flowers about 2 millimetres across are borne in axillary peduncled cymes of one to several flowers, often appearing flat-topped. The fruit is a small globose to subglobose dehiscent capsule about 2 millimetres in diameter, crowned by the persistent calyx and containing numerous minute angular brownish seeds.