252 SYSTEMATIC BOTANY. 



been seen by St.-Hilaire. The simple legume presents a great variety of 

 conditions, both of form, consistence; and dehiscence. Its normal form is 

 such as we see in the garden Pea (fig. 389) ; in Colutea (the Bladder-Senna) 

 it is inflated and membranous ; in Astragalus the dorsal suture turns in 

 and forms a false septum (fig. 372) ; in Phaca it is spongy or fleshy ; in 

 many cases it is woody ; it may be straight or curved, or even spirally 

 curled (Medicayo, fig. 371) ; in the lomentaceous form it is constricted at 

 intervals, often breaking into 1-seeded joints (fig. 370) ; in Cathartocarpus 

 it is cylindrical ; in Detarium and Dipteryx the 1-seeded ovary develops 

 a bony endocarp and fleshy epicarp, and becomes a drupe, like JTJ O . 373. 

 the Almond. The dehiscence is equally varied : normally 

 both sutures open and the valves separate ; in Hcematoxylon 

 the valves adhere at the sutures and split in the middle. In 

 Carmichaelia the valves separate from the suture ; in Orni- 

 thopuSj &c. the lomentum breaks up, and the pieces either 

 open or remain indehiscent; in Entada the lomentaceous pod 

 is opened by the valve? separating in pieces. In Catharto- 

 carpus, Arachis y Tamarindus, and other cases no dehiscence 

 occurs at all ; and in Cathartocarpus and Tamarindus a pulp 

 is formed inside the legume. 



The irritability of the leaves of many Leguminous plants 

 is a striking characteristic : it is most remarkable in the 

 Hedi/sarece, as in Smithia, Desmodium, &c., and in Mimosece ; 

 but it exists in a lower degree very commonly, even in the 

 Locust-tree (Robinia Pseudo-acacia}. The Acacias are no- ea 



ticeaBle for the phyllodial petioles, which often wholly re- of flowers, of 

 place the leaves (fig. 373). Acacia. 



Distribution. The Order comprises nearly 7000 species. The Papilio- 

 nacece are universally distributed, but are most abundant in warm climates ; 

 some genera are widely diffused, others almost confined to particular parts 

 of the globe, as Australia, North or South America, Cape of Good Hope, 

 &c. The CcemlpmiecB and Mimosece are chiefly tropical ; but the latter 

 abound beyond this limit in Australia. Traces of Leguminous plants have 

 been observed in the Lower Eocene and more recent formations. 



Qualities and Uses. This Order contains a vast number of plants ; and 

 among them there is an exceeding diversity of properties. Those with 

 mild juices are frequently exceedingly nutritious; when the juices are 

 more concentrated, they become either purgative or astringent, and some 

 of them poisonous ; the poisonous properties occur in all parts, but chiefly 

 in the seeds and bark. In other respects they furnish most valuable 

 timber, fibres, gums, dyes, &c. In enumerating some of the most im- 

 portant plants, it will be best to take them under the heads of the Sub- 

 orders. 



1. Papilionacea. A large proportion of the common fodder-plants,sucli 

 as Clover (Trifolium), Lucern and Medic (Medicayo], Melilotus, Sain- 

 foin (Onobrychis*), &c., belong to this Suborder ; and various other similar 

 plants are in use in foreign countries, such as species of Astragalus, Cro- 

 talariajuncfia, Desmodium diffusum, Indigofera cnneaphylla, &c. The seeds 

 of many species are eaten, constituting the various kinds of pulse ; such 

 as Broad Beans (Faba), Haricots and Scarlet-Runner Beans (Phaseolus), 



