On the Formation of Nodules in the Cortex of 
Hevea brasiliensis Muell.-Arg. 
BY 
G. BRYCE, B.Sc. 
Assistant Government Botanist and Mycologist. 
W ITH the development of the rubber industry and the 
planting of large areas in the Eastern Tropics under 
Hevea brasiliensis, a striking pathological condition of the 
cortex was brought to light. In the cortex of certain trees 
small woody bodies of varying shape and size were found ; 
these bodies were termed “ burrs ” or “ nodules.” As the 
rubber plantations became older and the trees bigger in girth, 
tapping operations to obtain the latex from the cortex were 
begun. These burrs or nodules, which were considered to be 
comparatively rare in untapped trees, now appeared to occur 
more frequently in trees where tapping had been in progress 
for some time. However, other circumstances might combine 
to render their occurrence apparently more frequent ; tapping 
operations would disclose their presence in trees where, 
perhaps, owing to little outward sign, they had not been 
suspected before. In parts of the tree not tapped their size, 
increasing with age, would ultimately result in their discovery. 
The presence of nodules of several years’ growth is at once 
detected by the characteristic, gnarled, and knotted appearance 
of the stem of a tree so affected. Tapping may be seriously 
interfered with, or even rendered quite impossible in trees 
badly affected. In a younger stage nodules may cause only 
a slight swelling externally, and they may then somewhat 
resemble the callus formed as a result of tapping injuries to 
the stem wood. 
Swellings on the Hevea stem were shown by Fetch (21) in 
1905 to be of two kinds. The first kind is caused by wounding 
the cambium of the stem, usually by tapping too deeply. 
Annals of the Eoyal Botanic Gardens, Peradeniya, Vol. VI., Part IV., Dec., 1917. 
6(14)17 (36) 
