EXOGENOUS OR DICOTYLEDONOUS PLANTS. 



413 



Calyx mostly of five sepals, more or less united ; the odd sepal in- 

 ferior (Fig. 358). Corolla of five petals, either papilionaceous or 

 regular. Stamens perigynous, or sometimes hypogynous. Ovary 

 single and simple. Fruit a legume, various forms of which are 

 shown in Fig. 580, 581, 800-807. Seeds destitute of albumen, or 

 with a mere vestige of it. — This immense family is divided into 

 three principal suborders ; viz. : — 



805. Subord. PapilionaceCB {Puhe Family proper), which is charac-- 

 terized by the papilionaceous corolla, — the vexillum always exter- 

 nal in estivation (471, Fig. 392), — ten diadelphous (Fig. 461), 

 monadelphous (Fig. 462), or rarely distinct, perigj-nous stamens,, 

 and the radicle bent on the lai-ge cotyledons. Leaves (rarely sim- 

 ple) only once compound ; the leaflets very rarely toothed or lobed. 



806. Subord. CaisalpineaB (to which Cassia, Cercis, and.the Honey- 

 Locust belong) : here the corolla gradually loses its papilionaceous 

 character, and always has the vexillum, or superior petal, covered 

 by the lateral ones in testivation ; the stamens are distinct, and the 

 embryo straight. The leaves are often bipinnate. 



807. Subord. Mimosea? (a large group, to which the Acacia and the 

 Sensitive Plant belong) has a perfectly regular calyx and corolla, 

 the latter mostly valvate in aestivation and hypogynous, as well as 

 the stamens, Avhich are sometimes definite, but often very numerous ;: 

 and the embryo is straight. The leaves are frequently tripinnate. 



FIG. 800. Open legume of the Pea, 801. Loment of Desmodium. 802. Loment of Mi- 

 mosa : b, one of its dehiscent joints which has fallen away from the persisting border or frame 

 (repluni), seen in 803. 804. The jointed indehiscent legume of Sophora. 805 A legume of 

 Astragalus, cut across near the summit, to show how it becomes partly or entirely two-celled 

 by the iutroflexion of the dorsal suture. 806. Similar view of a legume of Phaca, where the 

 ventral suture is somewhat introflexed. 807. A legume of Medicago scutellata, spirally coiled, 

 into a globular figure. 



35* 



