170 



knives are spoken of as having given good results. The use of 

 scrapers of any kincf is deprecated on the ground that in practice 

 they tend to clog the freshly opened latex tubes. There are four 

 principal methods in vogue of tapping trees, (a) single oblique 

 lines, (b) V-shaped incisions, (c) single oblique cuts joined by a 

 vertical channel ; known as " half-herring-bone" when all the cuts 

 are on one side of the vertical line, and "full herring-bone" when 

 on both sides, (d) spiral curves. The advantages and disadvan- 

 tages of the various methods are discussed. Owing to the favour- 

 able results obtained, the last method has recently gained favour 

 in Ceylon and elsewhere. The main stem is practically the onlj^ 

 part of the tree to be tapped and the greatest yields are obtained 

 from the lower portion, up to six feet from the ground level. Some 

 doubt appears to exist as to the quality of the latex obtained from 

 higher levels and contrary lesults are reported from different 

 localities. It is most important in practice to take advantage of 

 what is now generally known as the " wound response" which is 

 usually obvious within 24 to 48 hours after the first tapping. In 

 an experiment quoted the yield of latex obtained from the same 

 number of incisions, over approximately the same area on one tree, 

 increased from 61 cc. on the first tapping, to 449 cc. on the four- 

 teenth tapping, about two a half months later. Tapping every 

 day either for the whole of the rainy season or during alternate 

 months has given excellent results on a large scale on several 

 Ceylon estates. Trees to tap should, in Ceylon, be not less than 

 20 inches in circumference 3 feet from the ground and at least 4 

 to 6 years old. Such trees may be expected to yield I to 3 lb. of 

 dry rubber per tree up to their tenth year and much more in sub- 

 sequent years. Exceptionally well developed trees have given as 

 much as 12 to 25 lb. a year without shewing any ill effects or 

 signs of exhaustion. 



The general physical and chemical properties of latex are 

 briefly touched upon and analyses quoted of that derived from the 

 plant under discussion. The production of rubber from latex is 

 fully discussed, and the various methods and machines employed 

 are described, as also the purification, vulcanisation and uses of 

 rubber. 



The commercial varieties of Para rubber are enumerated, their 

 preparation described, and comparative chemical analyses given 

 of various kinds of plantation rubber from Ceylon and the Straits 

 Settlements. 



The recently established value of the seeds of Hcvea hrasilicnsis 

 as a source of oil is pointed out, as also the possible use of the 

 residual cake as a feeding stuff. The methods of transporting 

 the seeds in a living condition are discussed ; the best results 

 appear to have been obtained by packing them in powdered char- 

 coal and sawdust in sealed tins. The use of Wardian cases is 

 however still the most satisfactory method. A chapter is devoted 

 to the diseases of the plant, and an appendix contains estimates 

 supplied by planters of the cost of planting rubber in Ceylon. 



