THE HEVEA EUBBEE TREE IN THE AMAZON VALLEY 61 
METHODS OF COXSERA ATIOX OF SUPPLY 
Naturally, nothing is being done at present to conserve the available 
supply of caucho, and it is indeed doubtful whether there is any way 
to do this. At first glance the destruction of trees to secure a single 
crop of rubber seems wasteful in the extreme, and one is inclined 
to think that some method of repeated tapping might be employed. 
But the history of Castilla in cultivation shows some of the difficul- 
ties of this practice. 
In the first place Castilla can not be tapped frequently, but must 
be allowed to rest for some months after each tapping. This works 
against the tapping of wild trees, on account of the time which must 
be spent in hunting the trees in the forest. If trails are cut from one 
tree to another these will become overgrown between tappings, and 
it will be almost as difficult to relocate the trees as it was to find them 
in the beginning. This labor can be profitable only where the Castilla 
trees are much more numerous than is usual. 
The nature of the bark offers another difficulty. In this genus the 
bark is tough and fibrous and is so much injured by tapping that it 
dies back for some distance on either side of the tapping cut, leaving 
a gaping wound in which the wood is exposed. Regeneration of the 
bark over these wounds is very slow, and the exposed wood is almost 
always attacked by borers, which seriously damage the tapped tree 
and very frequently cause its death. 
A further objection is found in the nature of the latex, which does 
not readily flow along the tapping cuts, as does the latex of Hevea. 
Mention has been made of the tendency of this latex to separate into 
two portions. The light frothy portion blocks the channel of the 
tapping cut, and much latex flows down the bark of the tree and is lost. 
This can be obviated, partially though not entirely, by making the 
tapping cuts nearly vertical, but considerable loss is inevitable. 
When each tree is tapped only once or twice yearly the number 
tapped by one man would be very large and spread over an extensive 
area. This would necessitate frequent changes of base by the tapper, 
with duplication of dwellings, etc., an objection which weighs heavily 
against this system. 
In spite of all the objections, it is possible that caucho may be 
tapped successfully in some areas. The attacks of the borers may be 
prevented by the application in the tapping wounds of some sub- 
stance poisonous to the insects. Steeper tapping cuts might reduce 
the loss of latex, but the other objections appear insuperable except 
in regions where the stand of caucho trees is much denser than it is 
in general. 
SAPIUM 
Numerous species of Sapiuni occur in the basin of the Amazon, and 
several of these are known as producers of rubber. Rubber-bearing 
species of Sapium are known also in other regions, and at one time 
Sapium jenmanii was recommended for planting in British Guiana. 
One species of Sapium is common along the lower Amazon and 
at least some of its tributaries. This is generally known as itapuru 
or tapuru. By some it has been called S. oiglandulosum, but, 
according to LTe (42), the typical S. oiglandulosum is shrubby, whereas 
the plant in question is a tree of good size. The form found on the 
Jurua River has been named S. tapuru Ule. Whether this is the same 
