THE HEVEA RUBBER TREE IN THE AMAZON VALLEY 55 
and the islands area; but it is not possible to say to what extent the 
acknowledged superiority of the up-river grades is due to superior 
methods of preparation. To-day the difference in the methods 
of preparation between the up-river and the lower Amazon areas 
is very great, quite enough to account for great differences in 
quality. If such conditions have obtained in the past, they may be 
responsible for the reputations of the different grades of rubber. 
The yielding power of the different forms is also unknown, and 
truly comparative data can not be obtained at present. The trees 
near Para have been tapped for the longest time and are much 
mutilated. The condition of the bark is very bad, and this fact 
explains in part the poor yield of the trees in this area. The writer 
(20) found, as might have been expected, that there is a definite 
correlation between the rate of growth and the yield of rubber, and 
this fact further explains the low yield of the poorly grown trees of 
the lower Amazon. 
The relationship of the plantation trees to those of the Amazon 
has been a matter of interest to the plantation-rubber industry 
since its beginning. Practically all the plantation Hevea trees 
both in the Orient and in the Western Hemisphere are descended 
from seeds taken from Brazil to the Kew Gardens by Wickham in 
1876. It was commonly supposed that Wickham's introduction 
represented the lower Amazon type and that this accounted for the 
inferiority of plantation rubber. As better methods of preparation 
of plantation rubber were developed, less and less was heard of the 
inferiority of plantation rubber, until the prejudices of manufac- 
turers against this product have now almost entirely disappeared. 
The quality of plantation rubber has also improved as the age of the 
trees has increased. De Vries (4-3) and others have shown that 
rubber from young trees is inferior to that from more mature trees. 
However, the fine hard Para rubber of the up-river regions until 
very recently has been considered the only grade suited to certain 
special products, such as cut sheet, for example. The recently 
developed spraying method of coagulation produces a product which 
is considered by many authorities the full equal of fine hard Para 
rubber. 
Although fine hard Para rubber held the supremacy, conjectures 
were constantly made as to whether or not the up-river country did 
not contain a type superior to that introduced by Wickham. Wick- 
ham (46) insists that his seeds came from a high plateau between the 
Tapajos and the Madeira Rivers and that they were not like the 
poorly grown trees along the lower Amazon, though he does not say 
they differ in type. Huber (11) thinks Wickham's seeds came from 
the upper basin of the Rio Arapium, three days from Boim on the 
lower Tapajos, and states that the Tapajos rubber is now an in- 
ferior sort. 
It has been considered by some that Wickham's seeds represented 
a hybrid between Hevea collina and H. brasiliensis. Huber (10) 
says that H. coUina grows in the region from which Wickham 
got his seeds and considers it possible that he collected a few seeds of 
H. coUina along with the others. But in his studies of eastern plan- 
tation trees Huber was unable to find anything like pronounced 
characteristics of H. coUina, and he does not think the plantation 
type is a hybrid of H. coUina X H. brasiliensis. 
