Nov. X, 1902.] 
THE TROPICAL AGRICULTURIST. 
505 
THE INDIARUBBBR TREE: 
ITS LATEX-BEARING DUCTS. 
BY HENRI LECOMTK.* 
The latex of the caoutchouc plants is contained ia 
lacticiferous channels, whose distributiion varies with 
the catare of the plant and perhaps also with its bio- 
logical oonditidDs. It is evident that an exact know- 
ledge of the distribution of the laticifers (the latex 
bearing ducts) is iudispensible for fixing the regula- 
tions of methodical work. Unfortunately, this study 
has been neglected, so that tho processes of extracting 
the latix are altogether empirical. My present in- 
tention is not to consider all the cases that may arise 
but simply to call attention to certain facts and con- 
siderations, wnich may enlighten experimenters iu 
their researches. 
For example in the Landolphia Ueudelotii, which 
furnishes the larger part of the caoutchouc exported 
from the Senegal, the Soudan, and Guinea) in west 
Africa,) it is easy to recognize from a cross section of 
the Uano (climbing plant), that the laticifers are es- 
pecially distributed in the middle portion of tho bark 
bat are almost altogether lacking in the enter por- 
tion, as well as in the zone nearest the wood. 
To reach the laticifers, there is therefore need of 
penetiating through the baik. The latioiftrs of the 
Landolphia Ileudelotii are long tubes, ramified and 
anastomozed, whose diameter varies from 30 to -iS 
thousandths of a millimeter. These laticifers extend 
principally along the stem, but, as I have said, they 
are ramified, and these ramifications take a direction 
more or less oblique. 
A transverse section a h of determined length 
*nd depth, may, for example, encounter a number of 
luticifers and produce a proportionate number of 
orifices from which the latex will flow. A longitudinal 
incision c. d. of the same length and depth; will meet 
a much smaller number. 
The inspection of the figure (1) will render further 
explantation snpeiflaous; but it is not difficult to 
demonstrate the fact at 
least in the case of the 
Landolphia Heudelotii. It 
is known — and this is 
the point of depar- 
ture of the processes 
of the extraction of tho 
caoutchouc from dry bark- 
that the la'ex coagulates 
spontaneously in the latici- 
fers of the baik when it 
dries, so that each laticifer 
of dry b:irk contains a very 
thin filament of rubber. If 
a piece of dry bark is broken 
and the two fragments sepa- 
rated carefully, they are seen 
to be united by a multitude 
of rubber filaments, the 
number being equal to that 
of the laticifers encountered 
by the section (Fig, 2.) 
Let this section be made 
perpendicularly to the 
length of the stem, or paral- 
lel to this length : the fila- 
ments are still found in la; ge 
number if the section is 
crosswise, but in small 
number only if it is longi- 
tudinal. Fig. 3 drawn 
FIG. I. 
Theoretic representation of 
the arrangement of the lati- 
cifers. 
a b— Cross section meeting 
sii: laticifers. 
(I— Loiifritudiual section 
meeting only one laticifer. 
•Translated from the Journal d' Agriculture Tropical e 
(Paris, April 30, 1902), tor The India Rubber Would. 
The suggastious contained in this article were pre- 
sented in a popular lecture on " Caoutchouc and the 
Plants which Furnish It" delivered by this botanist at 
Palis, on March 4, under the auspices of the French 
Asaociatioa for the Aivauooment of the Sciences. 
FIG. 2. 
Two pieces of bark 
broken apart cross- 
wise, but still con 
n?ctefl by a large 
number of caout- 
chouc filament^. 
from nature, exhibits this clearly. 
A piece of bark of rectangular 
form was separated in to p^iria 
by a perpendicular section along 
the length of the stem; the 
two portions were still con- 
nected with nnmorous fila- 
ments of rubber. If one of these 
fragments was afterwards broken 
in two parts, by a section 
pan llel with the axis of the 
stem, and the two parts a 
end fc separated, as shown in 
Fig. 3, they were seen to be 
connected by a small number 
only of thin threads of rubber, 
cause such a section meets a much 
less number of laticifers than acroaa 
section of the same extent. 
We may, therefore, consider 
rv=; , r''"Ti! demonstrated that two equal 
£ -J 'r.^- ^ incisions made in the bark 
will encounter very different 
numbers of the laticiferous ducts 
according as the section is 
longitudinal few laticifers or 
transverse many laticifers ; it is 
not difficult to conclude that tha 
cross section will cause a much 
greater quantity of the lat^.x to flow 
than the longitudinal section. This 
is very easily shown on 
living climbing plants 
belorgirg to the genua 
Landolphia. 
I have also verified 
the fact on a young 
Castilloa clastica, which 
Was placed at my disposal 
by Messrs. de V^ilmorin. 
l>i;. Morris, in his Cantor 
lectures, published in the 
Journal of iJ,e Sodeiij of 
Arts Loudon has stated 
that in tlie trees of 
the genus Uevea, culti- 
vated in the Henarat 
gcda garden . in Ceylon 
other things being equal 
the oblique incisions. (45°) 
produced about tw'ce ns 
much as the vertical inci 
sions. . 
The transverse incisions 
have another advantage 
with reference to the gath- 
ering of the latex. In con- 
sequ-nce of the constant 
growth of th el gneous cylin- 
der surrounded by the b.irk 
the latter, not following 
this growth, is stretched 
more and more, like a too 
narrow garment, around too 
volum inons a body. It is 
this tension of the bark 
which causes the longitudinal cracks, so characteristic, 
for example of the surface of the bark of an oak tre?. If 
an annular cross band of bark is removed from the trunk 
of a tree, and the attempt afterwards made to replace 
it at the spot from which it was taken, the two ex- 
tremities will not meet. 
It is precisely this tension which causes the fljwof 
the latex, which the capillarity would keep, in tha 
absence of this intervention, in the interior of tha 
laticiferous ducts. Inmaking a cross section, the 
tension of the tissues above and below this section is 
not modified. The result is that the latex will fljw as 
freely as possible. A longitndiual seotioc. somewhat 
extended, would, on tha contiary, produce difforeuli 
Pi 
FIG. 3. 
Hiustration e.xh bitina; 
the caoutfhouc fliments 
connecting two scrips of 
bark. 
Between a and b, the 
filament? proceeding from 
the transversal inoscula- 
tions. 
Between a 6 on one side 
and c on the other, the 
filaments correspond to 
the laticifers encountered 
by a cross section. 
39 
