54 
in some other way deliberately bleed them to death, they still tap 
them with an utter disregard of all precautions for their preserva- 
tion. Such methods are out of the question when we come to tap 
the trees on the rubber plantation. Here absolutely the first con- 
sideration is not only to conduct the tapping in such a way as to 
preserve the life of the tree but even to prevent this operation from 
injuring its vigour and growth. 
It does not require much demonstration to show that the process 
of tapping must to a considerable extent depend upon the position, 
distribution and arrangement of the laticiferous vessels in the trees. 
It is generally stated that the milk-ducts of rubber trees lie in the 
layer of bast underneath the bark, and that no milk-ducts are to be 
found in the inner parts of the trees, the wood or cambium. This, 
as a general statement may be true enough, but it certainly does 
not strictly apply in the case of Castilloa elastica. If we chop one 
of the stout branches off a Castilloa tree, or, better still, if we cut 
down a young tree, and carefully examine the cut, we can easily see 
with the naked eye that although the bulk of the exuding latex 
issues from the layer of bast immediately beneath the bark, still 
there are quite a number of apparently rather large milk-ducts 
distributed through the wood of the tree, and also that there is a 
considerable exudation in the lignified tissue surrounding the pith 
centre of the trees. It will be a highly interesting problem to as- 
certain by a carefully microscopic study of the various strata of the 
trunk of the Castilloa tree, whether there is any direct communica- 
tion (anastomose) between these widely separated milk-ducts in 
the various parts of the tree. How far similar conditions exist in 
other rubber trees, I am at present unable to say, but it seems tc 
me very improbable that Castilloa stands alone in this respect. 
Whether there is any communication between the milk-ducts in 
the different parts of the tissues of the trunk of Castilloa or not, 
can however, not alter the fact that in tapping the trees on a rub- 
ber plantation only those layers of the trunk situated on its peri- 
phery can be drawn upon. Indeed, it is the layer of bast only 
immediately underlying the bark which is worth considering for 
tapping purposes, as it is generally admitted that any cuts into the 
wood of the tree are liable to permanently injure, or even altogether 
destroy it. It is therefore quite clear that as regards fhe rubber 
plantation entrusted to me, one of the most important questions to 
be solved was to ascertain and decide upon the most satisfactory 
method of tapping the trees. 
A microscopic examination of longitudinal sections of the bast 
layer of Castilloa at once revealed the fact that while this layer 
contains an enormous number of milk-ducts running longitudinally 
through the tissue, there are surprisingly little evidence of lateral 
intercommunication (anastomoses) between them. In exact agree- 
ment with this observation is the fact that longitudinal incisions 
produced an absurdly small flow of latex, indeed, in many cases, 
none at all, this for the simple reason that the number of milk-ducts 
opened by a vertical incision is, in the absence of horizontal branch- 
ings, simply the number of milk-ducts occupying the width of the 
