| 1 | Stamens twice as many as sepals. |
| 1' | Stamens as many as sepals, very rarely more in some flowers. |
| 2 | Seeds pluriseriate, free (not embedded in endocarp). |
| 2' | Seeds at least below uniseriate and embedded in endocarp. |
| 3 | Plant subglabrous to appressed-pubescent. Capsule terete. Petals 5-17 by 4-17 mm. Style 1.5-3.5 mm. Raphe equal in diameter to the body of the seed |
| 3' | Coarse, strongly pubescent or villous plant. Capsule strongly 4-angled, villous, with flat sides. Petals 15-24 by 16-26 mm. Style 1 mm long. Raphe not more than ¼ the diameter of the body of the seed |
| 4 | Seeds in the c. ¼ upper part of the capsule pluriseriate and free. Sepals 4. Petals 2-3 mm long |
| 4' | Seeds all uniseriate in each cell of the capsule and embedded in endocarp. Sepals 5-7 (rarely 4). Petals 4.5-23 mm long. |
| 5 | Aquatic, with floating branches forming erect clusters of spongy, spindle-shaped aerophores (aerenchyma). Petals white or creamy, with yellow at the base |
| 5' | Plant not forming such aerophores on the decumbent branches. Petals bright golden-yellow with a darker spot at the base. New Zealand, Australia, Pacific Is., Formosa, China, and Japan, also in the New World, might possibly be found in East Malesia. Cf. ASTONAquat. Pl. Austr.1973144f. 55 |
| 6 | Seeds pluriseriate in each cell of the capsule. Petals elliptical, 1-3 by 0.7-2 mm. Capsule terete. Seeds 0.3-0.5 by 0.2-0.25 mm |
| 6' | Seeds uniseriate in each cell of the capsule. Petals narrow spathulate, 1.3-2.2 by 0.4-0.9 mm. Capsule slightly 4-angled. Seeds 0.5-0.6 by 0.3 mm |
