t)EC. 1, 1902.) THE TROPICAL 
AGRICULTURIST. 
latex, from which 49 lb, of rubber were obtaineS 
and he declares this an aver,tge yi^ld of all trees, 
the trunk of which, before branching out, reaches 
a height of from 18 to 27 feet above the soil. In 
Nicaragua it is found that from its sixth or seventh 
vear a Castilloa tree yields from 4 to 6 lb. of rnbber 
annually (Crawford). Dr. Morris states that a Cas- 
tilloa, when first tapped, should yield 16 lb. of rubber. 
In Mexico, it appears to be generally assumed that 
Castilloa trees, when from 4 to .5 years old, will 
produce an aveiage yield of 6 lb. of rubber. However, 
the " Bureau d' Informations Agricoles du Mexique " 
is rather more careful, giving the yield of the trees 
in question as amounting to from 4 to 5 lb. of latex, 
corresponding to 2 lb. 6 cz. of rubber. 
J. H. Hart (Trinidad), states the yield of Castilloa 
as amounting to from 2 to 6 lb. but from quite a 
recent communication, I tal;e it that au experimental 
tapping of one of his largest trees only produced 
about 14 oz. of rubber. 
According to these above set out statements we 
would have to come to the delightful conclusion 
that, from its sixth or seventh year Castilloa elaatiea 
will yield frnm 6 to 49 lb. of rubber annually. 
On the other hand, we have the results of the 
experiments of Dr. Trimen, Superintendent of the 
Botanical Gardens of Ceylon, and these results are 
as follows : — 
5 years old. Mean yield of 77 trees : 2 3 oz. per tree. 
6 „ ,, 61 „ 2-0 oz. „ 
8 „ „ 61 „ 1-8 oz. 
12 ,. „ 61 „ 4-3 oz. 
My chief reason for quoting Dr. Trimen's figures is 
merely to call renewed attention to the absolute 
necessity of carefully ascertaining the yield of the 
Castilloa tree iu any district in which it is intended 
to cultivate it. Dr. Trimen's figures can not be 
looked upon as representing the yield of Castilloa 
elastica anywhere but in Ceylon or Javn, but they 
convey a vivid idea as to the extraordinary degree 
to which different conditions of soil and climate 
may affect the yield of rubber. 
My own results obtained at Las Cascadas are as 
follows : — 
Age Yield Per cent, of Yield of 
of tree. of latex. rubber in latex. rubber. 
6 1 lb. 13 oz. 26 ' 7-5 oz. 
7 2 „ 5 „ 26 9-6 „ 
8 3 „ 1 „ 29 14 2 „ 
11 5 „ 3 „ 31 1 lb, 9-7 „ 
As the trees can with perfect safety be tapped twice 
yearly, the annual rubber yield may be taken double 
that in the last column of the above table. These 
yields, as regards the trees of 8 aud 11 years of sge, 
respectively, are the means of a number of fnily- 
developed trees of the two respective ages. The 
yields of the younger trees above given were obtained 
on tapping two representative trees of the respective 
Bges, and taking the mean of the yield obtained as 
the real yield. I consider the above figures rather 
below than above the maik. But it is nevertheless 
well worth pointing out that as even Castilloa trees 
of the same age are apt to exhibit astonishing 
differences in their development it is only to be 
expected that they do so likewise as regards the 
quantity of rubber they produce, and it is, perhaps,' 
not an altogether sate procedure to ascertain tie 
aggregate yield of a rubber plantation by simply 
multiplying the number of trees on the plantation 
with the, however carefully, ascertained yield of a 
limited number of trees. It is further my opinion 
that the method of planting and rearing young 
rnbber plantations, always speaking of Castilloa 
elastica, is a matter deserving of much closer and 
more careful study than it has so far obtained. 
The method of simply planting out in a forest clearing 
eo many seeds, or feedlings, at so many feet distance 
I consider, altogether inadequate. With this highly 
important matter I propose to deal at some future 
The question regarding the best method of tap- 
ping the rubber trees is one which ju.st now is 
engaging the attention of most of those occupied 
rubber planting. Of course, there are always the 
methods of the natives to fall back upon, but it 
could not be said that these are on the whole cal- 
culated to inspire much confidence this for the 
simple reason that the native collectors in all partt) 
of the world never show the slightest regard for 
the trees they are tapping. If they do not actually 
cut the trees down, or iu 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 consideration is not only 
to conduct the tapping in such away as to preserve 
the life of the tree, but even to prevent this opeia- 
tion from injuring its vigour and growth. 
TAPriKG. 
It does not require much demostration 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 ol: 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 eg 
a general statement may be true enough, but it 
certainly does not strickly apply in the case of 
Castilloa elastica. If we chop one of the stout branchc a 
off a Castilloa tree, or, better still if we cut do:vn 
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 lignetied 
tissues surrounding the pith centre of the trees { 
It will be a highly interesting problem to ascertain 
by a careful microscopic study of the various strata 
of the trunk of the Castilloa tree, whether there is 
any direct communication (anastomose between these 
widely separated milk-ducts iu the various parts 
of the tree. How far similar conditions exist in 
other rubber trees I am at present unablo to say, 
but it seems to 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 rnb- 
ber plantation only those layers of the trunk situated 
on its periphery can be drawn upon. Indeed, it is 
the layer of bast only immediately underlying the 
bark which is worth considering for tapping pur- 
poses, 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, there- 
fore, quite clear that as regards the rnbber planta- 
tion entrusted to me one of the most important 
questions to be solved was to ascertain and decide 
upon the most satisfactory method of tapping tha 
trees. 
A microscopic examination of longitudinal sections 
of the bast layer of Castilloa at once revealed tha 
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 agreement 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 tho 
number of milk-ducts opened by a vertical incision 
is, in the absence of horizontal branchings, simply 
the number of milk-ducts occupying the width of 
the cut in the horizontal direction. Compared with 
the total number of milk-ducts ia the la^-ec of basj 
