42 
BULLETIN, 1422, U. S. DEPARTMENT OF AGRICULTURE 
In general, the condition of the bark on the trees in the lower 
river region is very bad. Both virgin bark and renewed bark are 
very thin and hard. Table 9 gives bark thicknesses and numbers of 
latex-vessel rows for a number of trees from various points in this 
area. Most of the data are from untapped bark, but on very old 
trees it is often impossible to be sure that any of the bark from the 
ground level up to a height of 10 feet is really virgin bark. However, 
the greater part of the data in Table 9 are from untapped trees and 
certainly represent virgin bark. 
Table 9. — Bark development of rubber trees on the lower Amazon 
Locality 
Num- 
ber of 
trees 
Age of 
trees 
(years) 
Character of bark 
Cir- 
cumfer- 
ence of 
trees 
at 1 
meter 
(cm.) 
Bark 
thick- 
ness 
(mm.) 
Rows 
of latex 
vessels 
Remarks 
Colonia de Outeira.. 
Do 
15 
28 
4 
15 
22 
22 
1 
4 
1 
2 
1 
7 
9 
4 
3 
6 
14 
18 
28 
4 
6 
3 
29? 
12 
20 
Very hard, little 
latex. 
Very thin and 
hard. 
Much tapped 
6.6 
11.1 
13.4 
11.7 
10.1 
17.5 
13.5 
11 
12.5 
12 
13.3 
9 
14.1 
14.3 
16.3 
14.3 
15.8 
8.7 
10.6 
9.3 
15.5 
17.1 
25 
16.3 
Grown among fruit 
trees, no culti- 
vation. 
Old stumps of trees 
Pinheiro (old trees) . . 
Japacany Island 
Japacany Island (old 
jungle trees). 
141.3 
~"~4.T 
cut years ago. 
11 
Much tapped . . . 
do 
raraca (old jungle 
trees). 
2? 
3? 
4? 
3.0 
4.4 
5.5 
6.3 
3 
5.6 
5.1 
5.3 
6.5 
7.1 
4.3 
5.0 
4.1 
6.8 
6.3 
12.0 
5.8 
Do... 
47.1 
Do 
ped trees) . 
Cocal Grande, near 
Obidos. 
Do 
19 
21 to 22 
23 to 24 
25 to 26 
(?) 
24 
11 
13 to 14 
Bark very hard 
do 
....do 
102.0 
124.5 
138.8 
148.7 
129.3 
170.5 
58.0 
93.2 
69.1 
Do... 
Do 
do 
do 
do 
do 
Do._- 
Do 
Seed from Purus. 
Do 
near Obidos. 
Do 
Parintins . . 
15 + 
Itacoatiara (old 
trees). 
Cainama (very old 
Bark fairly hard.. 
166.3 
trees) . 
Cainama (planted 
trees) . 
The thinness of the bark and the small number of latex vessels 
are shown by these data, which were taken from 246 trees. With the 
exception of a few at Itamaraty all the trees are 11 years old or over, 
but the bark thickness and the number of latex-vessel rows are far 
below the means of 9.05 and 20.78, respectively, for the average area 
in Sumatra already mentioned at eight years. Only three very old 
trees at Cainama were above this average bark thickness; these also 
had an average number of latex-vessel rows higher than that of the 
Sumatran area. But these trees were undoubtedly well over 20 
years of age. 
The few trees at Itamaraty are very exceptional in girth as well as 
in bark thickness and number of latex vessels, if the ages given for 
these trees are correct. But there is very great doubt whether the 
ages are even approximately correct, both because the development is 
