RUBBER PLANTING 67 



TABLE XIII 

 Yield of dry rubber in three years from a single tree. 



Total Rubber Average per 

 No. of 

 Section 

 I. 

 II. 

 III. 

 IV. 

 I. on renewed bark 



not completed 150 30,508 203 



In three years the total yield was nearly 240 Ibs. 

 of dry rubber. This was contained in about 70 gallons 

 of latex, or nearly 20,000 cubic inches. The total 

 area of the bark tapped during this period was about 

 10,000 square inches. The thickness of the laticiferous 

 bark was about half an inch, so that the volume of the 

 bark actually subjected to tapping was about 5000 cubic 

 inches. It is by no means an easy matter to estimate 

 the volume of latex vessels contained in a given volume 

 of bark, owing to the marked shrinkage of the former 

 when the bark is removed from the tree. It will be safe 

 however to assume that the total volume of the latex 

 vessels is not more than one-tenth of the total volume 

 of the bark, and most writers upon the subject have 

 given a considerably lower estimate. We have therefore 

 obtained in three years 20,000 cubic inches of latex by 

 tapping an area of bark which did not contain more 

 than 500 cybic inches of latex at the beginning of the 

 experiment. The problem before us is to account for 

 the remaining 19,500 cubic inches of latex. 



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