DIV. II 



ANGIOSPERMAE 



667 



There are no representatives native to Europe of this family, which is 

 abundant in the tropics. The Sensitive Plant (Mimosa pudica) (Fig. 291) occurs 

 as a weed throughout the tropics and exhibits great irritability to contact. 

 Numerous species of the genus Acacia are distributed through the tropics 

 and sub-tropics of the Old and New Worlds ; some are in cultivation in the 

 Mediterranean region. The Australian forms of the genus are frequently 



FIG. 703. Tamarindus indica. (| nat. size. After A. MEYER and SCHUMANN.) OFFICIAL. 



characterised by possessing phyllodes (Figs. 136, 192), the vertical position of 

 which contributes to the peculiar habit of the Australian forests. Some American 

 species of Acacia are inhabited by ants (Fig. 699) which live in the large stipular 

 thorns and obtain food from Belt's food-bodies ( 25 ) at the tips of the pinnules. A 

 mutual symbiosis has not been demonstrated in this case. Many species of Acacia 

 are of considerable economic value owing to the presence of gums and tannins in 

 the cortex or in the heart-wood. A. catechu (Fig. 700) and A. sum a are East 

 Indian trees from Avhich Catechu is obtained. 



OFFICIAL. By the disorganisation of the parenchyma of the stem of Acacia 



