14 BULLETIN 1422, U. S. DEPARTMENT OF AGRICULTURE 
rubber, which is considered inferior in most markets. As the average 
seringueiro is not so cleanly as to care greatly what falls into the 
latex while it is coagulating, the coagulum usually contains various 
impurities. 
The lumps of rubber which have formed in the latex in the cups, 
in transit, or in the basin are squeezed into an irregular mass, to which 
is added the film formed on the surfaces of the various utensils. 
Little attempt being made to keep this rubber clean, it is usually 
found to contain a considerable percentage of impurities. This 
low-grade rubber is called sernamby. 
In some places the latex is smoked over a square paddle. The 
yield for one day only is»smoked; then the layer of rubber is cut open 
at the upper end of the paddle and the paddle is pulled out. This 
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Fig. 5. — Rubber awaiting shipment on the banks of the Madre de Dios, at Conquista, El Beni, 
Bolivia The balls are of finelhard Para rubber; the bales are of caucho rubber 
leaves the rubber in a flat cake rectangular in outline. It is called 
knapsack rubber, presumably from the cavity in the cake formed by 
the paddle. At Tres Casas, on the upper Madeira River, such rubber 
is prepared in large quantities and is said to command the best price 
in Manaos (fig. 6). 
Around Para, in the delta region, the rubber is much less carefully 
prepared. The latex is allowed to coagulate in the cups, and the 
rubber is then collected and pressed into irregular masses. Some- 
times the latex is poured into holes in the ground to coagulate. 
According to Lange (15), the resulting coagulum is often allowed 
to stand in water for months with the idea that it will absorb water 
and increase in weight. 
As a result of such practices this rubber comes into Para in a wet, 
stinking, and indescribably filthy condition, and it would likely find 
