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BRYCE : 
of this is the abnormal occurrence in which shoots can some- 
times be produced from such burrs, there being a definite 
organic connection between the shoot and the core of the 
burr.” 
Fetch in his book on Hevea brasiliensis (23) considers that 
tapping has some effect in leading to the formation of nodules, 
and that there is no support for the statement that these burrs 
“ work out ” if left alone. “ The production of burrs is not 
a universal habit of Hevea brasiliensis ; indeed, they are com- 
paratively rare on untapped trees freedom from burrs 
is a character which should be required in the selection of seed 
bearers.” Fetch comes to the conclusion that burrs are not 
caused by insects or fungi. 
Rutgers in Java, in his description of canker in Hevea (27) 
in 1912, says that nodules are an after-result of an attack of 
canker. From behind the canker areas a brown colouration 
spreads out in streaks ; these streaks reach the inner cortex 
and then expand and discolour large areas. These brown- 
coloured streaks and areas are composed of dead cells, and 
they remain in the bark long after the external cankered area 
has disappeared. They are apparently not caused by the 
fungus itself, but rather by poisonous products emanating from 
the fungus. The living cells round these dead areas begin to 
divide, and ultimately nodules are formed. Nodules are thus 
a secondary result of an attack of canker. Rutgers does not 
explain how the poisonous products, in their passage through 
the tissue intervening between the cankered area and the inner 
cortex, leave that intervening tissue unaffected. This appears 
to be a serious objection to his hypothesis. 
Bateson translated (4) and discussed Rutgers’ paper in 1913. 
Later he published a discussion (5) on the formation of nodules, 
in which he records from his observations that nodules arise 
on old leaf scars, although some occur between old leaf scars, 
and many occur at the base of old trees, where the leaf scars 
are totally obliterated. The vascular strand of the leaf passes 
through the cortex of the main stem and joins up with the 
central vascular system. When the leaf falls, the part of the 
strand in the main cortex remains there more or less isolated, 
and in the further growth of the main stem it loses its connection 
