RUBBER PLANTING 51 



repeated. It follows that there must be a certain 

 optimum rate of tapping for any given tree. Experi- 

 ence alone can determine this rate. A sound judgment 

 upon this point is perhaps the most important item in 

 the equipment of the successful rubber planter. Some 

 knowledge of the experimental work which has been 

 done by others, will, however, be found useful in setting 

 out to acquire the necessary experience. 



The Functions of Latex. 



The fact that the latex vessels are entirely separate 

 from the channels in which the food-bearing sap is 

 transported, gives rise to the natural question: what is 

 the use of these latex vessels to the tree, and what is 

 the precise function of the milky emulsion which they 

 contain? This is a point upon which we are still 

 very much in the dark. From the fact that the great 

 majority of trees of all kinds get on perfectly well 

 without latex, we are driven to the conclusion that this 

 substance is not essential for the life of the plant. It 

 is certainly the case that large quantities of latex can be 

 removed without causing any visible injury to the health 

 of the tree. The fact that the removal of latex stimu- 

 lates the tree to the production of large additional 

 quantities of this substance, having nearly the same 

 composition as the latex originally present, suggests 

 that the formation of latex cannot be regarded merely 

 as the excretion of a waste product. On the contrary, 

 the conclusion seems inevitable that latex is formed at 



42 



