24 
BULLETIN 1422, U. S. DEPARTMENT OF AGRICULTURE 
taken out with the borer and showed 117 and 96 rings, respectively, 
which is equal to a diameter increase of 4.26 and 5.43 millimeters, 
much like that shown in the other trees. 
Table 3. — Age of Hevea trees as indicated by their annual rings 
Locality 
Circum- 
ference 
of tree at 
1 meter 
(cm.) 
Number 
of annual 
rings 
Locality 
Circum- 
ference 
of tree at 
1 meter 
(cm.) 
Number 
of annual 
rings 
Kilometer 10, near Porvenir, 
f 128 
164 
\ 140 
151 
I 169 
f 106 
120 
\ 108 
106 
I 116 
69 
95 
74 
89 
74 
79 
77 
101 
122 
138 
Fazenda Palmaris, Acre Ter- 
ritory, Brazil: ■ 
Very little crowded 
60 
24 
f 9.5 
7.6 
\ 8.5 
7.0 
I 9.4 
21 
Arroyo Limonao, on Rio 
Madre de Dies (in jungle).. 
10 
8 
8 
7 
10 
130.8 
91.8 
If we accept such diameter increases as typical, the trees in the 
estradas on the Rio Ouro Preto in Matto Grosso and at Sena have 
an average age of 128.3 years; those at Porvenir and Fazenda 
Palmaris average 86.5 years; and the big trees at Sena are 185.3 
years old. The largest tree seen by the writer, with its girth of 395 
centimeters, should be 278 years old-. Trees 5 and even 6 meters in 
circumference are reported by creditable observers, so it is entirely 
f)Ossible that rubber trees which were growing when Columbus 
anded on the continent are still living in the remote jungles. 
The idea that Hevea is a jungle tree and therefore can not thrive 
outside the jungle was ardently advanced in the early days of rubber 
planting. It is still held by many South Americans, who think 
planting must be done under the jungle cover if success is to be 
obtained. Whether this is true or not may be learned from Table 3, 
where the growth of young trees in the jungle is shown at Fazenda 
Palmaris and Arroyo Limonao. All observations at other places 
show the same thing — that the growth of the trees is extremely slow 
until they reach the level of the jungle crown and receive a proper 
share of light. 
The number of seedlings which reach a considerable age is very 
small. In many places small seedlings are rare, possibly because the 
old trees are not bearing seeds or possibly because the seeds are eaten 
by animals. It is not unusual to find trees which have many open 
fruits beneath them, though not a seed is to be found. Deer are 
said to be especially fond of the seeds, as are wild pigs. 
In other places seedlings from 1 to 2 feet in height are plentiful, 
sometimes even hundreds under a single mother tree. But of these 
very few reach a greater size, and the percentage of Hevea trees is 
not increasing. Where the old trees are being tapped the percentage, 
of course, is decreasing rapidly. 
There is no question that the growth of trees under the jungle 
canopy is very slow indeed compared with that of trees in the open. 
In some places attempts have been made to plant trees in estradas, 
but usually no clearing whatever was done around the young trees 
