62 
BULLETIN 1422, U. S. DEPARTMENT OF AGRICULTURE 
as that of the lower Amazon is not certain, but it seems likely that such 
is the case. The Amazonian form was called S. prunifolium by 
Klotz, but Mueller Argoviensis considers S. prunifolium a form of 
S. biglandulosum. 
Itapuru rubber was formerly listed, according to Akers, as third 
in quality of the Amazon rubbers; the black rubber was considered 
best, with the white next. Other writers consider this rubber about 
midway between Para and caucho in quality. 
At present there seems to be no itapuru rubber in the market, 
although there is no doubt that latex from Sapium trees is frequently 
mixed with He Yea .latex. Figure 14 shows a Sapium tree being 
tapped on an estrada with He Yea trees. In some places the collectors 
do not consider that the Sapium latex lowers the quality of their 
rubber, but eYen regard Sapium rubber as superior to that of HeYea. 
The writer found the raw rubber from such trees to be Yery tough 
and resilient, but was unable to procure samples for further tests. 
Nor could any data be obtained concerning the response of the tree 
to repeated tapping. The seringueiros apparently tap any Sapium 
trees which they encounter in their estradas, but pay little attention 
to them. . 
The trees themselves showed that they have been tapped fre- 
quently. The scars showed that they had much greater ability to 
regenerate their bark than Castilla trees, though large slow-healing 
wounds are much more common than in HeYea. 
The trees of Sapium seen by the writer were all tall, with straight 
columnar trunks and rather small branches. The bark is reddish 
brown in color, but is usually gray from the growth of lichens. A 
thin shell on the outer bark is dark red and very hard and brittle. 
Inside of this the bark is Yery soft and rather fibrous. It is very full 
of a latex which closely resembles that of Hevea brasiliensis. 
A microscopical examination of the bark shows that the latex 
vessels are Yery numerous; they appear to be arranged in rows, like 
the latex Yessels of HeYea, but close examination shows that the 
rows, if they are rows, have relatively few vessels in them and are 
very closely crowded together. An attempt was made to count the 
rows of vessels in the bark of several trees at Itamaraty, Para, Brazil, 
but on account of the crowding together of the rows, the counts 
can not be considered more than approximations (Table 15). 
Table 15. 
-Observations of latex vessels in the bark of Sapium trees at Itamaraty, 
Para, Brazil 
Bark 
Rows of 
Bark 
Rows of 
thick- 
latex 
thick- 
latex 
ness (mm.) 
vessels 
ness (mm.) 
vessels 
3 
8 
6 
29 
6.5 
25 
5 
18 
6 
15 
6 
53 
6.5 
26 
9 
130 
If the trees at Itamaraty on the lower Amazon were no older than 
they were said to be, they have made a remarkably rapid growth. 
Several trees said to be 4 or 5 years old averaged 25 centimeters in 
diameter and one alleged to be 6 years old was about 80 centimeters 
