36 BULLETIN 1422, U. S. DEPARTMENT OF AGRICULTURE 
tamination would be a decided advantage, while the bark and earth 
rubber could be collected without great expenditure of labor and 
would add to the income of the collector even though the price were 
low. At present practically none of this is collected in most estradas. 
RUBBER RESERVES OF THE AMAZON VALLEY 
It is doubtful whether anyone knows even the approximate number 
of trees in the Amazon Valley which have been exploited. As to the 
virgin trees even less is known, but it is known that there are great 
areas in which rubber trees occur in considerable numbers. In some 
of these areas the rubber trees are said to be a large percentage of the 
stand. General Rondon, the leader of the Roosevelt-Rondon ex- 
pedition, is reported by Oakenfull (29) to have found a great area of 
jungle in Matto Grosso, between Porto Velho and Cuyaba, where the 
rubber trees occur in an almost pure stand. In a letter to the writer 
General K-ondon said the report of Oakenfull was probably not quite 
correct, but the proportion of rubber trees in many places was sur- 
prisingly high, perhaps as great as 50 per cent. 
Lecointe (25) estimates that on the lower Amazon the jungles have 
8 to 10 rubber trees per hectare; in the Acre district there are about 15 
per hectare; while in some parts of Matto Grosso there are as many as 
25 per hectare. Akers (1, 2,) states that in general the rubber trees 
are from 200 to 250 feet apart, which appears to be nearly correct. 
Lecointe 's percentages are certainly higher than will commonly be 
found. Doubtless there is great variation in the stand of rubber trees 
in different places, but the writer doubts whether the tappable rubber 
trees average more than 2 per cent of the stand of the Amazon- 
ian jungles. But even at this rate the number of rubber trees is very 
great, perhaps not hundreds of millions, as Akers states, but certainly 
many millions. 
These trees offer a real reserve of rubber which would be available 
to the Western Hemisphere in case a crisis of any sort cut off the 
Eastern supply. In such a case the price of rubber would quickly rise 
to a point which would make exploitation of these trees possible, and 
a large quantity of rubber could be secured in a short time. 
Modern methods of tapping could be used on these virgin trees, and 
such methods could the more readily be applied because the greater 
part of the tappers would be new men who had never tapped by the 
older methods and who could easily learn the new ones. 
The greatest difficulty in this exploitation would probably be the 
rapid recruiting of labor for the industry, and transportation facilities 
would need great improvement and extension. 
Whatever the difficulties may be, there is no doubt that a serious 
shortage of rubber would lead to the exploitation of these trees. For 
the present there is little likelihood that these reserves will be drawn 
upon, but they will remain a great resource until such time as a need 
for them arises. 
PLANTATION POSSIBILITIES IN THE AMAZON VALLEY 
It was a great disappointment to the members of the expedition not 
to be able to find any plantation of rubber trees which had been 
planted and maintained in the same way as a good oriental planta- 
tion. If such a planting exists there it was not located, though many 
planted trees were seen. Therefore, it is impossible to make direct 
