22 
BULLETIN 1422, U. S. DEPARTMENT OF AGRICULTURE 
In Brazil there is normally only one dry season, and the rings of 
growth may be accepted as a rough measure of age. Counts of 
rings made for a number of trees in Brazil and Bolivia are shown in 
Table 3. Some of the trees were felled, but in most cases borings 
Fig. 7. — An old Hevea tree at Diamantino, on the Madeira River, which has been tapped for more 
than 30 years. Dr. Raymundo Monteira da Costa, rubber specialist with the Brazilian Commis- 
sion, is standing by the tree 
were made with an increment borer which cuts out a cylinder of 
wood extending from the bark to the heart of the tree. The rings 
show clearly in such a cylinder, and the age of a tree may be de- 
termined without damaging: it. 
