FORMATION OF NODULES. 
279 
No trees had true nodules. 
In the 2,000 trees not one case of large nodular masses 
was observed, nor have such cases ever been noticed in 
untapped trees examined on many estates in various parts 
of Ceylon. It may be objected that untapped trees are too 
young to show nodule formation on a large scale. On one 
estate eleven -year old trees which had been in tapping only 
two weeks were examined ; no trees showed large nodular 
masses. On the Experiment Station, Peradeniya, six-year 
old trees were brought into tapping in 1910, and in 1912, when 
eight years old, had developed large nodular masses in many 
cases. Tapping thus apparently supplies conditions favouring 
the rapid growth of nodules, though it is not necessarily an 
essential factor in their inception, and age is a negligible factor. 
Nodules can be distinguished from globular shoots with 
certainty only under the microscope. A nodule when cut 
through the centre exhibits a dark brown point or line at the 
centre of the cut surface, and this can be used as a rough means 
of distinguishing it from a globular shoot, which has no such 
colouring. In the nodule the dark brown colour is due to the 
presence of the tannin cells surrounding the altered latex 
vessels. Globular shoots in untapped trees have evidently 
been frequently mistaken for nodules, and probably are 
usually the bodies in question when nodules are stated to 
occur in untapped trees. 
Of the six cases of nodular structures obtained in the 2,000 
untapped trees, three were found in the callus at the edge of 
long vertical wounds. In these the structure was not typically 
nodular ; the rubber strands in the core occupied a cavity 
into which the latex had evidently oozed and coagulated, 
The cavity may have originated through internal lesions in 
the cortex, or through slight wounding by some external 
agency. 
In the fourth case there was a large cavity filled with rubber 
at the base of a globular shoot ; the cavity was closed over by 
subsequent layers of wood elements. The wood tissue of the 
structure at this point showed signs of a former callus nature, 
and without doubt this was a case of a globular shoot which 
had become exposed, possibly through the natural shedding of 
