March 2, 1903.] THE TROPICAL 
A.aRICULTURIST. 
587 
first eight renewals of the V incisions gave 131 J ounces 
of v]et rubber, as against 95J ounces of dry rubber when 
tapped with small herring-bone incisions. Assuming 
that the loss on drying was 50 per cent and counting 
" renewals " as ' incisions ' the figures read ; — 
ounces ounces 
200 (V) incisions gave 131 j wet rubber=65-75 dry rub- 
ber 
95 50 
As there were five V incisions on each tree, and the 
two lines forming the V were each G inches long, the 
exposed surface totalled up to 5 feet per tree._ When 
the same trees were tanped with small herring-bone 
incisions, the total len<;th of the incisions was 6 feet, 
regardless of the central channel which was not opened 
after the first day ; so that although the length of 
incisions in the latter case only exceeded those of the 
the former by one-fifth, the yield increased by one- 
third. The fact that the trees were twelve months 
older at the time they were tapped with herring-bone 
incisions, probably accounts to some extent for the 
extra yield obtained when tapped by the latter 
method. 
When compared with the yield from those trees 
tapped by herrinf •bone incisions, confined to the lower 
3 feet of the trunk this system may be considered very 
successful. The total length of the incisions was the 
same in each experiment, ftz , 6 feet, but if the yield 
for the first eight days of the trees enumerated in 
Table V be totalled up, we shall find that 30 feet of 
incisions (made on five trees an'i renewed on eight 
occasions; gave 105i ounces of wet rubber (say 52 
ounces dry ss |against 95* ounces of dry rubber 
obtained from 30 feet of incisions (on five trees and 
renewed on eight occasions) made on various parts of 
the tiuuk. In short, nearly twice the amount of 
rubber was obtained from the same length 
of incisions, when the whole area of the trunk was 
operated upon, and the cost of extraction therefore 
reduced by about one-half. This, however, is only 
the result of a single experiment and the results 
cannot by any means be considered conclusive. So far 
as they go they strenthen the supposition that if a 
maximum yield is to be obtained at, a minimum cost, 
which— assuming the operations are always conducted 
in the same careful manner— is paramount to a maxi- 
mum yield with a minimum injury to the tree, 
tapping must not be confined to any particular area. 
Other experiments in this direction are in progress and 
the results will be made known from time to time. 
One point which has not yet been noticed, is the 
lapidity with which the wounds heal, when made a 
considerable distance apait. 
{d). Length end distance heticccn the inciaions.—^he 
length of the vertical channel in some of the experi- 
ments already alluded to, was 3 feet but incisions of 
this length are not recomended, the objection being 
that part of the latex coagulates before reaching the 
tin, especially in hot dry weather. The length of 
the " feeders " will depend upon the girth of the tree, 
but tor the same reason it is inadvisable to make them 
more than 1 foot long even on the largest trees. 
"When taping young trees, they should be shorter 
in proportion to the circumference of the trunk, so 
as to avoid any risk of cliecking the growth of the tree 
by preventing a free passage, for the conveyance of 
the crude sap absorbed by the roots, to the green parts 
of the plant, there to be elaborated into starch and 
other organic compounds which supply the essential 
constituents for the formation of new structures and 
replace the material consumed during the growth of 
the plant, 
It may be taken for granted, that in a given area, 
the greater the number of incisions the greater the 
yield ; also that if the same number of incisions be 
made over an area, say twice the size, the yield would 
be consider. ibly more ; bat I do not hold, however, 
even assuming this to be the case, that it is expedient 
to make the incisions closer than 1 foot apart, aa 
the extra yield obtained is not in proportion to the 
extra labour entailed ; while on the other hand if the 
oblique incisions are made wore than this distance 
apart, the result will be a vertical channel of an 
undesirable length. Farther, cicatrization of tho 
wounds is considerably delayed, if the incisions are 
made too close together, as the amount of growing 
tissue in their immediate vicinity is necessarily 
limited. 
(2). The effect of irounding on the flow of latex. — 
Perhaps the most important point of all to be con- 
sidered, is that of taking full advantage of what 
has previously been alluded to as " wound effuct.'' This 
phenomenon, which appears to be well known to the 
natives of Brazil, was first scientifically observed by 
Mr. J. C. Willis, Director of the Peradeniya Gardens, 
and is mentioned in a circular issued by the Ueylon 
Botanical Department*: the result of a series of ex- 
periments on the effect of wounding on the flow of 
latex by Mr. Parkins, being set forth in a later 
circular, issued by the same Department t and to 
which I am indebted for many valuable sug- 
gestions. 
The function of the latex is not yet properly under- 
stood, but it is quite distinct from the sap, occoring 
in comparatively few plants and is probably unes- 
sential to the life of the tree. The effct of wounding 
the tree appears to cause an increased flow of lates 
towards the injured part, for if the wound be re- 
opened on the following day, the yield is nearly 
always found to be considerably in excess of that 
obtained on the occasion of the original tapping, 
sometimes threa or four times as much. Also, if 
the wound is opened again on the third day, the 
yield is found to exceed that of the second, and 
generally the yield of the fourth day exceeds that 
of the third and so on. 
(a). The number of times the incisions can be advan- 
tageously renewed. 
Many experiments have been made with a view 
to determining the number of times it is advisable 
to-reopeu the wound, but it was found that all trees 
were not affected in a similar manner, so that it is 
impossible to lay down any hard and fast rule ; 
for although in some cases the maximum yield has 
been obtained on the fourth day, in others it was not 
reached until the fourteenth tapping. 
Generally, however, the flow shews a marked increase 
between the first and second tapping, then a steady 
increase until the fifth or sixth tapping is reached, 
afterwads remaining mtjre or less stationary until the 
operations ceased ; in the large majority of cases 
there were no signs of falling off, even after the 
incisions had been renewed a dozen times, but by 
his time the wound had of course become very 
large and it was deemed advisable to stop opera- 
tions. 
Below I have summarised the results of several 
experiments, made with a view to ascertaining the 
number of times the incisions should be renewed. 
The trees experimented upon were tapped on the 
herring bone system, previously desoiibed, and the 
incisions renewed by taking off a very tbiu layer 
from each side of the wound with a sharp knife 
on 14 occasions. 
* Royal Botanic Gardens, Ceylon. Series 1— No. i, 
t do do do —No, 13, 
13. 11 
