Class 15. Tetradynamia. Stamens 4 long and 2 short. Orders 2, perfectly natural. Flowers cruciform.
1. Siliculosa. Fruit a roundish pod, or pouch. In some genera it is entire, as Draba, Engl. Bot. t. 586, and the Honesty or Satin flower Lunaria: in others notched, as Thlaspi, t. 1659, and Iberis, t. 52; which last genus is unique in its natural order in having unequal petals. Crambe, t. 924; Isatis, t. 97; and Bunias, t. 231; certainly belong to this Order, though placed by Linnæus in the next.
2. Siliquosa. Fruit a very long pod. Some genera have a calyx clausus, its leaves slightly cohering by their sides, as Raphanus, t. 856; Cheiranthus, t. 462; Hesperis, t. 731; Brassica, t. 637; &c. Others have a spreading or gaping calyx, as Cardamine, t. 1000; Sisymbrium, t. 855; and especially Sinapis, t. 969 and t. 1677.
Cleome is a very irregular genus, allied in habit, and even in the number of stamens of several species, to the Polyandria Monogynia. Its fruit, moreover, is a capsule of one cell, not the real two-celled