14 - 



required by the root-system and the base of the tree; secondly, 

 -on the quantity of available reserve material ; thirdly, on the 

 quantity of organic matter, which can still be transported down- 

 Awards through the unsevered channels ; and fourthly, on the 

 rapidity with which the reproductive activity of the cambium can 

 provide a substitute for the severed channels on the spot operated 

 upon. Consequently it is impossible to predict off-hand the 

 number of channels in the bast and the cortex, the severance of 

 which will sooner or later kill the tree. This can be ascertained 

 only by experiments suitable to each species of tree. 



From the foregoing remarks, it is evident why, at the 

 commencement of this chapter, I expressed the opinion that 

 tapping incisions on rubber plants will result in a certain amount 

 of injury to the trees. 



B. The Applicability of the Facts Enumerated to Rubber 



Trees. 



Is it, however, at all possible that these conclusions founded on 

 observations made on totally different species of trees, are applicable 

 to rubber plants ? May not their sap-circulation be subject to 

 totally different rules ? Do we not find in them quite a special 

 system of tissues, which is lacking in most other trees, and which is 

 diffused throughout the whole tree : the system of latex ducts ? Is 

 it not possible that this system takes an active part in the sap-trans- 

 port, and that the latex itself contains many important transportable 

 nutritive substances ? This theory is still very universally adopted 

 by many practical men. Botanical research has of course often 

 been occupied with the question. The results have been very 

 lucidly summed up by Kniep in a very excellent treatise, which 

 appeared not long ago, 1 and in which also a number of new 

 and critical experiments on different kinds of laticiferous plants 

 have been communicated. On the basis of his own experiments 

 and those of his predecessors, Kniep arrives rightly at the 

 conclusion, that in all probability, latex is not a nutrient juice, 

 and that it is consequently of no importance as regards the 

 circulation of sap. What mostly interests us is the conclusion 

 at which Kniep has arrived by experiments in girdling the branches 



1 Kniep, Hans. " Ueber die Bedeutung des Milchsafts der Pflanzen. 

 Flora." Vol. i, 94, 1905. Pp. 129, ff. 



