ORDER LEGUMINOS^E ; PAPILIONACEOUS PLANTS. 423 



tremely rich in plants useful in various ways to Man. Some 

 furnish him with a large quantity of wholesome and palatable 

 food for himself, such as the Pea, Bean, Lentil, &c. ; whilst 

 others afford equally nutritious food for cattle, such as Clover 

 and Lucerne. Others yield valuable dyes, such as Indigo and 

 Logwood ; and others again have stems which serve as excellent 

 timber, such as Brazil-wood, Rosewood, and the American 

 Locust-trees. From others are derived valuable medicinal pro- 

 ducts, such as Senna and Cassia, or Gums, as that of the Acacia. 

 Others, again, are attractive on account of their beauty, such as 

 the Laburnums, Robinias, &c. ; and others are interesting on 

 account of physiological peculiarities, such as the Sensitive-Plant 

 (. 421), the Gleditsias (. 238), and the New Holland Acacias 

 (. 228). Between all these there is a strong family likeness ; 

 but there is every variety of size among the very numerous 

 species which this order contains ; some being humble plants, 

 whilst others are lofty trees. The most important point in 

 which they all agree, is in the structure of their fruit, which is 

 a pod or Legume; whence the name of the order is derived. A 

 legume may be thus distinguished from all other kinds of 

 fruit. It is a carpel which grows long and flat, and separates 

 when ripe into two valves or halves ; it usually contains several 

 seeds, which are attached to one angle only of the inside of the 

 carpel. A Pea-pod is as apt an illustration as any that can be 

 furnished ; and, by referring to Fig. 96, the mode in which the 

 pod is formed from the carpellary leaf will be at once evident. 

 The ovules proceeding from the thickened edges of this leaf, 

 which are folded together, are attached alternately to the one 

 valve and the other ; so that, when the pod is opened along the 

 suture, or line of adhesion, (as is commonly done in shelling 

 peas) half the seeds remain attached to each valve and lie in its 

 hollow. The seed-vessels of all the plants of this order, how- 

 ever, must not be supposed exactly to resemble the Pea-pod; 

 they may be longer or shorter, larger or smaller, harder, thinner, 

 or differently coloured, or may contain more or fewer seeds ; but 

 they are always formed essentially upon the same plan. 



587. A very large number of the order are further dis- 



