171 
THE PRINCIPLES OF HEVEA TAPPING AS DETERMINED 
BY EXPERIMENT. 
By T. Percy, B.A., B.Sc., 
Government Botanist and Mycologist, Ceylon. 
[ ABSTRACT. | 
The early tappings of Hevea in Botanic Gardens and Ex- 
periment Stations were made simply to determine whether the 
trees would yield rubber, and, if so, how much. This phase 
is no longer necessary, and at the present time tapping experi- 
ments, which should, as far as possible, be conducted on virgin 
trees, should be designed to obtain further data on some 
definite problem. The experimenter should not be deterred 
by the criticism that his tapping problem is “‘ purely academic’”’; 
our knowledge of rubber tapping would have been in a far 
more advanced stage to-day if previous experiments had been 
restricted to “‘ purely academic ’’ problems. 
The first attempt to ascertain the fundamental principles of 
Hevea tapping was made in Ceylon in 1898 by Parkin, who 
used single-incision methods only. Parkin was followed in 
the Federated Malay States in 1901-2 by Arden, who also 
worked chiefly with single-incision methods, but in some ex- 
periments adopted an “‘ excision ’’ method in which the reopen- 
ings of the cuts were limited to fourteen. The ideas obtained 
from these experiments ‘have practically governed Hevea tap- 
ping until quite recently, although they were founded on quite a 
different form of tapping to that now adopted. Dr. A. W. K. 
de Jong has recently carried out fresh experiments in Java 
on some of’ the questions dealt with by Parkin and Arden, 
using modern methods of tapping, and his results afford a 
scientific foundation for the consideration of the problems 
involved. The experiments were conducted as a rule for a 
period of eight months, and it is pointed out that this may be 
a possible source of error in some cases; it is desirable at 
present that comparative tapping experiments should, with few 
exceptions, be carried on until the available tapping area has 
been completely tapped. ° 
The paper reviews the results obtained in various tapping 
experiments, with special reference to the different factors 
which are now known to influence such results, viz. (1) The 
area of the tapping surface; (2) the direction of the tapping 
cut; (3) the distance between the cuts; (4) the number of cuts; 
(5) tapping intervals; (6) the use of the pricker. The defects 
of the recorded experiments are pointed out where necessary, 
