Tree; calyx none; flowers monœcious, in heads. [Platanaceæ], [466]
Herbs; calyx present and commonly petal-like. [Polygonaceæ], [436]
Stipules not sheathing the stem, or none.
Aquatic herbs, submerged or nearly so.
Leaves whorled and dissected; style single. [Ceratophyllaceæ], [488]
Leaves opposite, entire; styles 2; ovary 4-celled. [Halorageæ], [180]
Not aquatics, herbs.
Ovary 10-celled; berry 10-seeded. [Phytolaccaceæ], [436]
Ovary 3- (rarely 1–2-) celled; juice usually milky. [Euphorbiaceæ], [451]