CLASSIFICATION 173 
plants and is widely distributed. It includes herbs, 
shrubs, trees and climbing plants. The roots of 
leguminous plants often have tubercles which are able 
to assimilate free nitrogen. The order is divided into 
three well-marked sub-orders, 
(1) Mimoseae. 
(2) Caesalpineae. 
(8) Papilionaceae. 
Fic. 95. 
A. Young fruit of the Pear. O. The ovary. B. Mature fruit, both 
longitudinally divided. (From Darwin's “ Elements of Botany ”’.) 
(1) Mimoseae.—F lowers regular, stamens numerous 
and free. 
Type.—Acacia (Mimosa or Wattle). This genus has 
about 400 species, mostly trees. Many are cultivated 
here for foliage and flowers ; some for their bark, which 
is used for tanning. One species of Acacia (the Karroo 
Thorn) has two white thorns in the place of the stipules, 
and several other species are thorny. > 
Leaves.—Alternate, compound, bi-pinnate, stipulate, 
