56 BULLETIN 1422, IT. S. DEPARTMENT OP AGRICULTURE 
Whether or not the species of Hevea hybridize readily is not 
known. Trees supposed to be hybrids of H. brasiliensis with 
H. confusa (5) were grown in the experimental garden at St. Clair, 
Trinidad. It seems to be accepted now that these trees were grown 
from a mixture of seeds of the two species and were not hybrids at 
all. No authentic cases of hybridity in the genus have yet been 
reported. 
So far as could be determined by this survey, the evidence indicates 
that the plantation trees belong to the white (branca) type of the 
lower Amazon. Whether this represents a type inferior to the up- 
river varieties is rendered doubtful by the excellence of plantation 
rubber as produced at present. It must not be forgotten that if 
rubber from the up-river types Were prepared by the most modern 
methods it might still be found superior to plantation rubber. The 
possibility is great enough to warrant a trial of these types in plan- 
tations. 
The true relationships of the various types and their relative worth 
to the plantation industry can only be determined by growing them 
all together under favorable conditions. A step in this direction 
has been made by the writer in the introduction of trees from the 
Acre region into the Canal Zone. A strict embargo on the exporta- 
tion of Hevea trees producing commercial rubber exists in the Brazil- 
ian States of Amazonas and Para and in the Acre Territory, and 
planting material could not be taken from these regions. Bolivia 
has no such embargo, and several hundred seedlings and the few 
seeds which could be obtained were taken from the Acre region of 
Bolivia to the Canal Zone and planted in the Zone Experimental 
Garden at Summit. 
Because of slow transportation, the material was a long time in 
transit and arrived in rather poor condition. It was planted during 
the dry season at Summit, where the conditions in general are not 
favorable for the growth of the tree. In spite of all care the seeds 
failed to grow, and most of the seedlings perished. A few still survive, 
and it is hoped that they will become established and aid in answering 
some of the questions which have been so often asked. At Summit 
they can be compared directly with trees of the plantation type 
which have been introduced from Trinidad and elsewhere. 
THE DISEASE SITUATION 
A detailed study of the diseases of the Hevea tree in the Amazon 
Valley is presented in the report of James R. Weir (4$), pathologist 
of the expedition, which should be consulted by those interested in 
this subject. In this report only the general phases of the disease 
situation as it bears on the rubber industry will be considered, with 
a few observations in regard to the regions not visited by Doctor 
Weir. 
In general it appears that the rubber planter in the Amazon region 
would meet about the same difficulties, so far as disease is concerned, 
as the oriental planter. Most of the ever-present parasites of the 
eastern plantations, such as Fomes (33), Diplodia (24), Gloeospo- 
rium (23) j and Pestalozzia (22), are found on seedlings or mature 
trees in the South American jungles and of course would invade the 
plantations. Many of them are present on these plantations now. 
