OF PLANTS. 191 



It will not be uninteresting to give a more detailed 

 account of these three families, and to mention the more 

 important plants belonging to them. 



The Spurges or Euphorbiacece constitute the most im- 

 portant group in reference to the amount of Caoutchouc 

 contained. From the Port of Para in South America, 

 from Guiana and the neighbouring States, an incredible 

 quantity of India-rubber is shipped for Europe, and this 

 is principally obtained from a large tree growing in those 

 regions, called the Siphonia elastica. In the year 1736, 

 the celebrated French savan, La Condamine, first directed 

 attention to Caoutchouc, and minutely described the mode 

 of obtaining it. That beautiful tree, the Siphonia, is 

 about sixty feet high, and has a smooth brownish-grey 

 bark, in which the Indians make long and deep incisions 

 down to the wood, from whence the white juice then 

 abundantly flows forth. Before it has time to dry, it 

 is spread upon moulds of unburnt clay, usually of the 

 shape of a small, roundish, short-necked bottle, and then 

 dried over a smoking fire. The spreading of the Caout- 

 chouc upon the mould is repeated until the coat has 

 acquired the desired thickness. By this operation, in 

 which the foreign matters are not separated from the 

 juice, which becomes still more contaminated by the 

 smoke, the Caoutchouc acquires a brown or black colour, 

 while pure Caoutchouc is white, or of a yellowish colour, 

 and semi-transparent. 



We owe a subsequent more accurate knowledge of the 

 tree and its distribution, to Fresneau, in the year 1751; 

 but especially to the indefatigable naturalist, Aublet du 

 Petit-Thouars. 



Many other plants of this group contain Caoutchouc, 

 but from none is it so easy to obtain it in large quantity. 



