22 
work of thinning ont drag’ging on for a long time, but there is less 
crop lost this way, as each round the trees which are not paying 
their way are removed, giving the advantage to the adjacent trees, 
the yield per acre is not greatly reduced and the cost of tapping is 
automatically reduced. 
With present day planting thinning out should not present any 
great difficulty as provision can he made for thinning out in 
the early stages. The time for thinning out is just as soon as growth 
is being hampered by branches interlocking, probably when the trees 
are about four years old. If a clearing is planted 20 ft. x 20 ft. with a 
view to thinning' out later to leave say 70 or 80 trees per re, the 
trees to be removed could be marked after careful examination 
and comparison with adjacent trees, and any branches interfering 
with the development of the favoured trees could be removed 
periodically as the necessity occurred. The marked trees could in 
this way be tapped for a considerable time in the regular round, 
enabling a fair return of latex to be obtained before they are finally 
removed and leaving them with very few heavy branches to cause 
damage while they were being felled. Of course} the ideal system 
would be to allow each tree eventually the same space, but this, I 
fear, would be impossible in practise, as weak unhealthy trees are 
frequently found side by side and have to be removed, while good 
trees have to be left near each other to make-up the number per acre. 
There are various methods of removing the tree. Some recom- 
mend pollarding the first stage, tapping the stump so long as it gives 
latex, then removing it. This system I have found not at all 
profitable. It is much more difficult to remove the pollard than it is 
the whole tree, as in the latter case the head gives leverage when the 
side roots are cut away, while the pollard has to be lifted bodily 
from the ground. The pollards yield very little latex after the first 
few tappings, and tappers are inclined to be careless with the tapping 
of them, and this carelessness, like other diseases, soon spreads to the 
good trees. The roots of the pollards too are still feeding and the 
adjacent trees are not benefiting to the same extent as if the trees to 
be cut out had been removed wholesale. 
Another system is to cut off the tree about a foot above the 
ground, but since the discovery of Udulina zonata I fancy this 
system is not much in favour. 
The most satisfactory way is to cut out the tree about two feet 
below the level of the ground, removing as many of the side roots as 
possible without interfering with the roots of the adjacent trees 
which are to remain. The cut out trees and branches should be 
burned, or otherwise removed as quickly as possible, to prevent an 
invasion of borers and the spread of disease. 
I have to thank the General Rubber Co., Sumatra, for the 
privilege of seeing their report on thinning out and for permission to 
use their recommendations. 
