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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. AVe know that the hairs are one mode of protecting 
the leaves against excessive transpiration. The latex is another 
means by which the tree prevents it,s 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 mdan to say or indicate that 1 consider 
the function of latex as solely one of water storage or prevention of 
too rapid evaporation. But field observations as well as laboratory 
and breeding experiments have conclusively shown that the protec- 
tion of the plant against too rapid transpiration is one ot 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 tempera- 
tures, near one of the trees standing about in the middle of the 
group of trees measured. I intended to return two hours later, when 
the full heat of the sun had been acting on the trees to re-measure 
the trunks in order to find out the shrinkage of the trunks at 
different times of the day. I was delayed, and returned some four 
hours ^Uer instead, at 10-47 a - m ‘ I he first thing I noticed was 
that one of the trees which in no way differed from its neighbours 
upon my first visit, was now looking very exhausted, with drooping 
branches and leaves hanging limply downwards. Another tree 
standing by looked perfectly fresh, while some of the others showed 
signs of having been slightly affected by the now scorching rays of 
the sun. This difference in power of withstanding sudden high 
temperature was so marked that I decided to try the different trees 
for latex. The result of a small cut in each tree was that A, the 
tree with drooping leaves, had no latex, while H , the most fresh ; 
looking tree of the lot, had plenty. Between these B, C, etc., 
showed a gradual increase in the amount of latex with the exception 
of two trees F and G, of which the latter had less latex than the 
former, but it was much thicker. This year I noticed the same 
difference at the end of January. Closer observation now revealed 
the fact that A had much more hairs on the leaves, petioles, and 
branchlets than H, and thus ought to have been better protected 
against too rapid transpiration. Counting the stomata on the 
leaves, I found that the number was smaller in A , — another 
protective device. The barkpores were almost equal. Five weeks 
later A commenced to drop its leaves, and was almost bare at the 
end of March, when H still had all its foliage left. A did not 
