Polygamia superflua,—the florets of the centre perfect or united; those of the margin with pistils only, but all producing perfect seeds.
Polygamia frustranea,—the florets of the centre perfect or united; those of the margin, in general, without either stamens or pistils.
Polygamia necessaria,—the florets of the centre with stamens only; those of the margin with pistils only.
The classes Monœcia and Dicœcia take their orders from the number and other peculiarities of the stamens:
| Monandria | 1 stamen. |
| Diandria, &c. | 2 stamens, &c. |
| Polyandria | 7 stamens. |
| Monadelphia | stamens united into one set. |
| Polyadelphia | stamens united into several sets. |
| Gynandria | stamens upon the pistil. |
In the class Polygamia there are three orders:
Monœcia. Diœcia. Triœcia.
The twenty-fourth class, Cryptogamia, has five orders:
1. Ferns.
2. Mosses.