FORMATION OF NODULES. 
261 
Fetch published a Bulletin (22) in 1909 on “ Abnormalities in 
Hevea brasiliensis,” in which is given the most detailed 
description of nodules up to that time, and the question of 
their origin is discussed. He found that nodules arise wholly 
in the cortex ; they increase in size, and may fuse together to 
form woody plates ; as they increase in size a projecting point 
appears on the inner surface of the nodule, and grows in 
towards the wood of the stem, with which it ultimately fuses. 
“ The formation of this point appears to be due to the pressure 
exerted by the developing core, which apparently prevents 
the formation of normal cortex between it and the wood of 
the stem at the points of nearest approach.” Latex obtained 
from the cortex over nodules is often of a yellow or chrome 
colour. Clots of almost dry rubber were obtained from 
pockets or cavities occurring where the cortex had died and 
become separated from the wood of the stem. Cross sections 
of nodules show a central nucleus of dead bark cells or of stone 
cells ; round these a cambium had been developed, and had 
given rise to a nodule by laying down wood cells and fibres 
internally and bark cells externally. 
Gallagher in 1909 attributed (11) the formation of nodules 
to early bad tapping, and believed them to be dormant buds. 
Later (12) he distinguishes three types of burr : his first two 
types are simply different stages of our nodule, his third type 
being the swelling due to the formation of wound wood on the 
main stem following a wound to the stem cambium. 
Bancroft in 1911 published a paper (3) on the occurrence of 
burrs on Hevea. He distinguished between nodules proper 
and swellings due to wounding the stem cambium. The 
nodules he attributed to the natural habit of the tree to produce 
dormant buds, which fail to develop into shoots. These are 
stimulated to activity by tapping, and give rise to nodules 
He mentions the production of woody masses in forest trees 
as a consequence of wounding or of increased illumination 
i after thinning out ; these woody masses originate from dormant 
buds stimulated to growth. “ The burrs on Hevea are similar 
in all respects to these above-mentioned structures. They are 
in their nature and mode of origin buds which have failed to 
develop into shoots. The most convincing evidence in favour 
