62 PARA RUBBER. 



composed of clay, the inner ridge being left open at the base of the in- 

 cision and the outer one continuous from top to bottom in the 

 half-herring-bone system, and both ridges open at the base of the 

 incisions when the full herring-bone system is adopted ; such a 

 channel is easily made, it lasts for quite a longtime, and in so far 

 that it does away with the vertical cut in the bark is to be recom- 

 mended. 



The illustrations given here and elsewhere show trees which ha ve 

 been tapped on this system in parts of Ceylon and Malacca. 



According to Ridley the tree has, for tapping purposes on the 

 herring-bone system , four sides , and may be tapped along one side 

 only during each year so that operations will be recommenced on the 

 tapping area of 1900 in 1905. This is a very gentle method, and has 

 much in its favour and can be used to advantage when tapping 

 according to exposure to the sun is adopted. 



The zig-zag system of tapping consists of a downward line join- 

 ing two oblique cuts, on opposite sides but at different levels, and so 

 arranged that the latex is collected at the base of the lowest incision. 

 This system is about the only one that can be recommended for trees 

 which, on account of previous bad tapping, have become gnarled 

 and woody on the surface ; the downward and oblique lines can be 

 made of any length and at any angle, and the knots thereby avoided. 



It has been pointed out* that vertical incisions lay open very 

 few latex tubes, and must in some degree have the effect of relieving 

 the tension, and may therefore cause a reduction in the flow of latex. 



Northway's and Bowman's Spiral Curves. 



A third method which has, on account of the good yields obtain- 

 ed, gained considerable favour recently in Ceylon and elsewhere is 

 the long spiral curve. The system consists of a series of parallel 

 cuts running round the stem and each ending separately at the base 

 of the tree ; or of shorter cuts ending at convenient places. The num- 

 ber of spiral cuts is determined by the circumference of the tree, there 

 being usually one curve for every girth of 12 to 18 inches at the top 

 of the tapping area. In this method of tapping a series of special 

 knives has been used which ensure the minimum waste of tissue 

 when re-opening the lower side of the wound. As this system has 

 given an average of 2 lb. per tree for each month's tapping at Pera- 

 deniya, and has been continued in some districts until a total of 

 161b. per tree in twelve months has been obtained, a detailed 

 description is here given. The illustrations on Plates 13 and 19, 

 Series A, show the stages from the beginning to the end of the first 

 cortical stripping. 



It cannot be doubted that the full spiral system is drastic, and 

 though excellent yields have so far been obtained by its adoption it 

 is as well to realize that the cortical stripping should not be effected 



* M, Henri Lecomte, Journal d'Agriculture Tropicalc, April, 1902. 



