AGRICULTURAL BULLETIN 
P 
OF THE 
STRAITS 
AND 
FEDERATED MALAY STATES. 
No. 6.] JUNE, 1907. [Vol. VI. 
ABNORMALITIES IN THE STEM 
OF HEVEA. 
Burrs. f 
The occurrence of burrs on the trunk of the Para-rubber especially 
in trees that have been cut or tapped has frequently been noticed by 
planters, and several letters have been received from time to time 
by the Editor containing enquiries on the subject. A portion of one 
letter from Mr. BURGESS I append, with some sketches by him. 
The burrs are more or less rounded, woody knots or tumours 
projecting from the bark. In small samples they are very easily 
knocked out of the trunk and are seen to be more or less globular 
or pear-shaped nodules of wood ending* in a short point, directed 
towards the trunk of the tree. They are covered outside with thick 
bark. And when knocked out of the tree leave a corresponding 
depression. In other cases they are larger and more irregular in 
outline, and cannot be detached. The largest I*have seen is on the 
erect branch of a prostrate rubber tree in the Botanic Gardens in 
Singapore. It is irregularly hemispherical or rather half oval, and 
measures 18 inches across, transversely, a foot long vertically and 
about 8 inches in thickness. The origin and cause of these! burrs 
is this. The Para-rubber tree like many others, produces during its 
growth a number of buds, which never developing into branches 
unless from some accident become in time ^covered with a later 
growth of wood, and are known as dormant buds. If a tree posses- 
sing dormant buds is cut down to near the base, these dormant 
buds may develop and appear as shoots. As every one knows in 
felling jungle if the stumps of the trees are not dug out, many will 
throw out shoots which may develop into full-sized stems. These 
are derived from the dormant buds. Frequently, too, use is made of 
dormant buds for propagation of plants which are otherwise difficult 
to reproduce. Thus in some of the Araliaceoe, such as Trevesia 
eminens, the stem frequently remains simple without branching. 
In order to make it throw out additional side branches either to 
