THE HEVEA RUBBEK TBEE IN THE AMAZON VALLEY 
41 
stunted and much below the size they should be for their age. The 
writer {20) found that a group of nearly a thousand trees in a repre- 
sentative area in Sumatra had an average girth of 80 centimeters at 
8 years of age, which is much superior to the growth of any of these. 
At Cacoal Imperial, also near Obidos, a number of trees were 
seen, all of them between 13 and 15 years old. Their growth is a 
little better than that of the trees at Cocal Grande, but they are not 
in a vigorous condition at present. 
The best area of planted rubber seen on the whole journey was that 
at Seringal Miry, an experimental planting near Manaos (fig. 11). 
Most of the trees were planted 30 by 16 feet apart on ground which 
had been plowed and prepared. Stumps were used for the planting, 
which was clone in 1915. Sixty of these trees were measured and 
Fig. 11. — Trees of Hevea brasiliensis at Seringal Miry, Manaos. This is the best area of planted 
rubber trees seen in the Amazon Valley 
were found to have an average girth of 72.3 centimeters at a height 
of 1 meter from the ground. 
A group of five old trees grown from seeds from the Jurua is also 
to be seen there. The age of these trees is uncertain — at least, efforts 
made to ascertain it were fruitless — but their size (178 centimeters 
average circumference) suggests that they are over 20 years old at 
the very least. 
At Cachoeira Grande, near Manaos, the Campo Experimental of 
the Sociedade Amazonense de Agricultura is located. The largest 
trees here are 12 years old and have an average girth of 88.7 centi- 
meters. All the trees are much neglected now, and practically 
nothing is being done to develop this once ambitious experiment 
station. 
A plantation here of trees about 6 } r ears old is in very bad condi- 
tion. All are stunted and unhealthy in appearance, and most of 
them are seriously attacked by die-back. 
