260 
BRYCE : 
thick scales and flakes of dry bark.” Aker’s statement, that 
nodules are practically unknown in the Amazon Valley, was 
made before his visit to report on that place, and appears too 
sweeping. The “ warty protuberances and knots ” mentioned 
by Cross, the “ mass of knots and warts ” mentioned by Akers, 
and the presence of nodules in Dutch Guiana reported by the 
Department of Agriculture there are together good evidence 
that nodules are not “ practically unknown in the Amazon 
Valley.” We may conclude that nodules occur in Hevea in 
its native habitat in Brazil. 
Previous Records. 
Gnarled stems early attracted attention in the East. Ridley 
in 1904 was the first to describe (25) knots on Para rubber 
trees : “ They are perfectly harmless, and have no connection 
with any fungus or insect bite, but are due to the irritation 
caused by suppressed buds in the stem The only 
objection to them is that they often interfere with the tapping 
cut, but they are easily knocked out if so, and if left are usually 
covered up eventually by the later growth of the trunk and 
so disappear.” 
Petch in 1905 published a more detailed description (21) : 
“ The structure of these knots is identical with that of the 
‘ maserknollen ’ (nodules) of beech and other trees. They 
are formed in the bark by an adventitious cambium, which has 
no connection with the main cambium of the stem.” 
In 1907 Ridley discussed (26) burrs more fully, and adduced 
some detail in support of his hypothesis, that they are 
derived from the abnormal development of dormant buds. He 
mentions that on some trees which had been tapped by the 
Brazilian method burrs had formed on the tapping cuts, and 
had later sent forth shoots. In the same Bulletin a corre- 
spondent describes nodules as occurring on tapped and untapped 
trees : the nodule begins as a small globule of wood, and has 
a spur point penetrating the main cambium and joining up 
with the wood of the tree. The suggestion is made that 
the pricker chips off and leaves small fragments of wood 
surrounded by cambium, and thus these unpleasant growths 
start. 
