DICOTYLEDONS : ARCHICHLAMYDEAE 245 



Sensitive Plant, Judas-tree, and Divi-divi. It is one of the 

 largest orders of flowering plants and contains 440 genera 

 and upwards of 7,000 species. All the British species have 

 papilionaceous flowers, and belong to the above sub-order. 

 Many species have nodules on their roots, by means of which 

 the plants can utilize atmospheric nitrogen and thrive in 

 soil deficient in nitrates. Many are climbers : the Scarlet- 

 Runner and Kidney Bean have twining stems, but many 

 climb by means of leaf -tendrils. Some are xerophytes 



Fig. 167. Floral Diagram of Sweet-Pea. 



with leaves reduced to phyllodes, as in some Acacias 

 (Fig. 96, 1), or the leaves are small and the stems angular 

 and green, as in the Gorse and Broom. The stipules are 

 often large, and in some cases e. g. in the Yellow 

 Vetchling {Lathyrus Aphaca) they perform the functions 

 of leaves, the remainder of the blade being transformed 

 into tendrils. 



The leaflets usually perform sleep-movements, and direct 

 the edges of the leaflets to the sky, some assuming the sleep- 

 position immediately when touched, e. g. the leaves of the 

 Sensitive Plant (Mimosa pudica). The flowers are adapted 



