60 RUBBER AND 



whereas in Central America it has frequently been the 

 custom to cut down the Castilloa trees in order that 

 the whole of the available rubber may be obtained at 

 one time. 



With the establishment of plantations, opportunities 

 for more precise observations soon arose. Among the 

 earliest experiments dealing with "wound response" 

 were those of Willis and Parkin, who first made use of 

 this expression. These experiments were carried out in 

 Ceylon and may here be recorded on account of their 

 historical interest. 



In 1897 Willis tapped a number of Hevea trees of 

 about two feet mean girth at intervals of a week with 

 the following result. 



TABLE VII 

 Willis. Average yield per tree (dry rubber). 



Ounces Ounces 



First week 73 Fourth week -80 



Second week 1*48 Fifth week -67 



Third week -97 Sixth week -52 



More elaborate experiments were carried out by 

 Parkin at Peradeniya in 1899, and the result of one of 

 these is recorded in the following table. 



TABLE VIII 

 Parkin (Latex, six Trees). 



March 25 ... 6ro c.c. 



30 ... 105-5 



April 6 ... 220*0 



12 ... 208-5 



15 ... 255-5 



20 ... 290-0 



25 ... 276-0 



May i ... 253-0 c.c. 



6 ... 264-5 



13 .- 275-0 



20 ... 255*0 



26 ... 262'O 



June I ... 328^0 



6 ... 449-0 



