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Description


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