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no question as to the fact that where several branches are allowed 

 to develop the growth of the main trunk is greatly retarded. 



It is therefore necessary to have a tree straight and clean boled, 

 in a condition to make the best of the period of maximum 

 growth, the time of which has not yet been ascertained. We 

 know for a fact that the best rubber producer has a thick, com- 

 pact crown. The conical form of crown is also to be recom- 

 mended as it naturally receives more light than a flat crown. 

 After the Castilla growing in the wild state has attained its maxi- 

 mum height the crown always becomes flat and rather ovate in 

 shape, while in youth, when the tree is growing vigorously under 

 normal conditions, it has a sharply conical crown. Every kind 

 of tree has a maximum height to which it is able to pump water, 

 and when this height has been reached the growth of the tree 

 ceases because the crown cannot be supplied with sufficient water. 

 The normal rubber tree should not, therefore, be very tall as in 

 the best situations the wild tree reaches a height of about sixty 

 feet, and the over-mature trees always have a very spreading 

 crown. Sometimes dry topped young trees are observed. This 

 is due to unsuitable conditions in some respect or another, and 

 we recognise this as a disease, called by foresters the " staghorn 

 disease." 



The leaves should be large, with a fresh green colour, the bark 

 thin and smooth. Some trees have leaves with stiff, bristly hairs, 

 and I have found on some plantations almost every tree covered 

 with these stiff hairs, sometimes resembling prickles. In cases 

 where such hairs occur the trees were below the average in regard 

 to yielding capacity. It seems therefore obvious that hairs should 

 be absent in the future type of rubber trees. There is also another 

 reason for this. We know that the hairs are one mode of protec- 

 ing the leaves against excessive transpiration. The latex is 

 another means by which the tree prevents its water supply from 

 evaporating too rapidly through the leaves. If we develop a tree 

 without hairs we should be able to force the tree into preparing 

 more latex in order to keep up the equilibrium, not allowing too 

 much water to transpire. 



REMARKS ON FUNCTION OF LATEX. 



By the above I do not mean to say or indicate that I consider 

 the function of latex as solely one of water storage or prevention 

 of too rapid evaporation. But field observations as well as labo- 

 ratory and breeding experiments have conclusively shown that 

 the protection of the plants against too rapid transpiration is one 

 of the functions of latex, at least in Castilla. 



I could give a number of proofs for this, but as the question is 

 more fully discussed in my handbook on Castilla, above referred 

 to, I will here mention only one instance, which first fell under my 

 observation in July, 1905. In walking through a stand of four 

 year old rubber trees, one early morning, I stopped and measured 

 some two dozen trees, which were especially well developed. I 

 noted down in my field-book certain characteristics of these trees, 

 and with my thermometers, took the soil and atmospheric temper- 



