128 AGRICULTURE IN THE TROPICS [FT. II 



comparatively insignificant figure, like that of collection of wild 

 cinchona bark, unless possibly in Brazil. 



Another important influence in determining the market 

 price of rubber is the fact that old rubbers can now be devul- 

 canised, and used again, and a vast quantity of this "reclaimed" 

 rubber is now being used for the cheaper qualities of rubber 

 goods. There have also been several scares about synthetic 

 rubber, which will doubtless come in time. Hitherto, however, 

 the cost of production of such rubber is much too great, and 

 the reduction in price of the natural rubbers will stave off its 

 arrival upon the markets. 



Para rubber, which is the only one whose cultivation has 

 assumed any importance, is strictly equatorial, growing within 

 about 10 of the equator, though it will also grow in southern 

 Brazil, which, while on the edge of the tropics, has a very 

 equable climate. It will grow up to about 2500 feet above 

 sea level, though only slowly above 1000 feet. It is usually 

 planted out from nurseries at about 15 25 feet apart, and 

 needs plentiful rainfall and good drainage. In suitable places 

 the trees increase in girth at the rate of about 4 inches a year, 

 and when they measure about 18 inches at a yard from the 

 ground, tapping usually commences, i.e. about the fifth year. 

 During the last few years it has been realised that excessive 

 tapping is a mistake, and that time must be allowed for the 

 new bark to form properly over the tapped places. The usual 

 method is now the herringbone for larger trees, the half-herring- 

 bone for smaller, a vertical groove being cut from the level of 

 the ground to about five feet up the bark, and lateral channels 

 leading into it at an angle of 45. The wound is renewed, and 

 the full effect of the wound-response obtained, by shaving off a 

 thin layer on the lower side of each of these lateral cuts every 

 day, or at less frequent intervals. Recent work done in Ceylon 

 by Dr R H. Lock seems to indicate that in the long run as 

 much rubber is obtained by the use of longer intervals, while 

 the bark of course is used up at a much less rapid rate, and 

 labour is saved. 



The milk runs down the central groove into a tin placed at 

 the base, and being collected and taken into the factory is there 



