66 BULLETIN" 1422, U. S. DEPARTMENT OF AGRICULTURE 
disease, just as all wilt-resistant cowpeas have been developed by 
the use of one variety. 
Aside from the question of disease resistance, these species may 
be useful in breeding work of other kinds. 
The extent to which crosses between species of Hevea may be 
made is not yet known and can be determined only by procuring the 
various species and experimenting with them. 
SUMMARY AND CONCLUSIONS 
A study of the Para rubber tree in the Amazon Valley was made 
for the purpose of obtaining information on the following points: 
1. The general status of the rubber industry in the Amazon region at the 
present time. 
2. The rubber resources of this region available in case of a crisis in the 
production or importation of plantation rubber. 
3. The suitability of the Amazon Valley for rubber cultivation. 
4. The types of Hevea growing in the Amazon region and the possibility of pro- 
curing more desirable strains for plantation use. 
5. The prevalence of diseases of Hevea and the general conditions regarding 
plant diseases in the region. 
The members of the expedition made studies along the Amazon, 
Madeira, Beni, Mamore, Pacanova, Ouro Preto, Madre de Dios, 
Purus, Acre, and Tahuamanu Rivers. The regions covered lie in 
the States of Para and Amazonas, in the Acre Territory in Brazil, 
and in the Beni and Noroeste districts of Bolivia. 
The genus Hevea is incompletely known both as to species and 
geographical distribution. The extension of knowledge depends on 
collections in distant regions, which are not likely to be made in the 
near future. 
The rubber industry in the Amazon Valley is in a precarious con- 
dition, primarily because of the low price of rubber. Certain alleviat- 
ing measures are suggested. 
The methods of collecting and preparing the rubber described are 
extremely wasteful of bark and of rubber. 
Tapping with the ax should be abandoned and should be superseded 
by the Amazonas knife where tapped trees are being worked. The 
Jebong knife should be used on virgin trees. 
Seringueiros collect from 600 to 1,000 kilograms of rubber in a 
tapping season of six months. 
Many of the rubber trees of the Amazon country are of great age. 
Some are hundreds of years old. Most of those in tapping are at least 
well over 50 years old. 
The wild trees of the Amazon Valley contain a great reserve of 
rubber which could be secured in case of necessity. 
All the rubber from this region comes from jungle trees. There 
are no plantations in production in the Amazon Valley. 
Great areas of land suitable for the cultivation of the Para rubber 
tree are available in the Amazon basin. 
The growth of rubber trees along the lower Amazon is generally 
unsatisfactory, and this region is not recommended for rubber 
planting. 
The well-drained uplands along the Madeira River and its tribu- 
taries, and especially along the Acre and the Tahuamanu, are promis- 
ing for plantation projects, at least so far as the growth and clevelop- 
ment of the trees is concerned. 
