28 RUBBER AND 



hard throughout, and offers considerable resistance to 

 tapping. The latex tubes are larger than those of 

 Hevea or Manihot^ and are entirely devoid of the cross 

 partitions which characterise the early stages of the 

 latter. Partly for this reason more rubber is obtained 

 at a single tapping, but the trees must then be rested 

 for a considerable time before a fresh supply becomes 

 available. The trees occur naturally in small groups 

 along the banks of running streams from sea level to 

 an altitude of 1 500 feet, but they do not grow well in 

 marshy soil. 



Tapping is carried out by making long slanting 

 cuts in the bark, sometimes extending right round the 

 tree in the form of one or more spirals. The flow of 

 latex is complete in 24 hours, and in some districts the 

 tree is then cut down in order to obtain the whole of 

 the available latex. The latex is acid in reaction, and 

 coagulation is effected by the addition of the alkaline 

 juice of certain plants or of a solution of soap. The 

 process is sometimes carried out in rectangular pits in 

 the ground lined with clay. The rubber thus obtained 

 contains numerous impurities. Owing to its greater 

 purity, the rubber which has dried on the tree fetches 

 a higher price. 



Other American Species. 



Hancornia speciosa, the source of Mangabeira rubber, 

 occurs in the South- West of Brazil and extends as far 

 south as Rio de Janeiro. It grows on plateaux at 



