PARA RUBBER. 85 



stood that the} r ield from trees of the same age may be doubled, 

 trebled, or quadrupled within a year by a change in the method of 

 tapping, and that those methods usually give the largest yields 

 which tap the latex tubes over the largest area. 



It should also be remembered that individual trees, either from 

 internal or external causes, show considerable variation in the quan- 

 tity and quality of latex they give, though of the same age and 

 tapped in a similar manner. At Henaratgoda, where the trees 

 range in age from 15 to 30 years, and where tapping has been done 

 on various sections of the trees from the base to 6, 16, 20, 30, 

 and 50 feet, the opportunities to observe the variation in yield of 

 latex and rubber have been numerous. The first six feet from the 

 base, though tapped over the same area, in the same manner, and 

 with the same implements, have given a yield varying from six 

 twenty-fifths of an ounce to nearly two ounces of rubber per 

 tapping per tree ; other parts of the stems of individual trees have 

 varied in their daily yield of rubber from three-fifths of an ounce to 

 five and one-fifth ounces, one-quarter to one and one-twentieth 

 ounces, nine-fortieths to thirty-three fortieths of an ounce, &c, and 

 in one case, where the tree has been regularly tapped from the base 

 to a height of 50 feet, the yield of dry rubber has sometimes been as 

 high as eight and three-quarter ounces per tree per tapping, and 

 on other occasions as low as a quarter of an ounce. Such 

 variations can, in most cases, be mainly attributed to internal 

 conditions rather than external climatic forces. Results of tapping 

 operations are available from different countries, and it will be 

 best to commence with those obtained in Ceylon. 



Rubber Yields in Ceylon. 



The yield of rubber varies from 7 lb. per 400 trees in one 

 tapping to a maximum of 25 lb. per tree in twelve months' tapping 



The first series of reliable yields* are those obtained at Hena- 

 ratgoda from 1888 to 1896. One tree at Henaratgoda was lightly 

 tapped every second year, and gave for nine years an average annual 

 yield of H lb. of dry rubber : — 



This tree was twelve years old when first tapped, and the 

 annual yield of Ih lb. was from the 12th to the 20th year of the tree's 

 life. The method of tapping consisted of scraping off the rough 

 outer bark and making numerous V-shaped incisions to a height of 

 about five feet. The tree had a circumference of 50| inches and was 

 growing with other trees of nearly equal size, distanced 30 feet apart. 



Other experiments have been made at Henaratgoda which in- 

 dicated similar results by consecutive weekly tappings of the trees. 



* Dr. Trimen, Notes on Rubber Experiments. 



