previous arrow
next arrow


Aquatic, amphibious or terrestrial, annual or perennial, glabrous herbs. Stem creeping, ascending, erect or floating, simple or branched. Inflorescence axillary, solitary or spicate, in almost every axil. Flowers 4-5 merous, sessile, 2-bracteolate, bracteoles almost equalling the flower. Hypanthium campanulate or tubular-campanulate, membranous in fruits. Epicalyx present or absent. Petals persistent. Ovary oblong, globose or 3-angled, 2-4 celled, placenta clavate, styles short. Fruit a capsule, 2-4 valved, faintly horizontally striate. Seeds elongated or round.

Key to the species

Serial Key Reference
1a. Leaves whorled. Flowers solitary, axillary R. mexicana
1b. Leaves decussate 2
2a. Stems broadly 4-winged R. densiflora
2b. Stems terete or 4-angled, not distinctly winged 3
3a. Calyx in fruit campanulate, tube longer than broad 4
3b. Calyx in fruit hemispheric, tube as broad as or broader than long 5
4a. Flowers in close set terminal spikes; capsule 4-valved. Leaves orbicular R. rotundifolia
4b. Flowers axillar, always solitary; capsule 2-valved. Cauline leaves elliptic, leaf margin translucent opaque R. indica
5a. Flowers distinctly pedicelled, distant below, approximate above. Leaves narrowly oblong R. simpliciuscula
5b. Flowers sessile 6
6a. Leaves elliptic oblong; stamens always 5 R. rosea
6b. Leaves narrowly oblong, sub cordate at base; stamens sometimes 6. Petals fimbriate R. fimbriata