FORMATION OF NODULES. 
287 
these buds experience only temporary retardation. At a 
later date they may begin a slow process of growth, but having 
lost their connection with the stem and receiving an inade- 
quate supply of food material, they are unable to develop 
normally, and thus globular shoots are produced. 
The case of nodules is somewhat different, and here we 
undoubtedly have a new formation. The production of these 
nodular bodies is induced by a definite determining cause, 
namely, the alteration in the latex vessel content, where 
under normal conditions they would not be produced. As 
this alteration in the latex vessel content advances along the 
latex vessels, it is accompanied by the laying down of nodular 
wood round the latex vessels ; this is illustrated in the fiat 
plate -like nodules of net structure with projecting points at 
the top and bottom ends. 
In tapping operations on estates numerous opportunities 
occur for the transference of this abnormal nodular condition, 
if it is transferable, from affected trees to non-affected trees. 
From the small number of trees affected it must be concluded 
that it is not transferable, but rather that affected trees have a 
predisposition to alteration in the latex vessel content. This 
would affect estate practice, in that great care should be taken 
to select seed for planting from trees free from nodules, as 
recommended by Fetch in 1906. 
The question arises as to whether the alteration in the latex 
vessel content is brought about by external causes or by 
unknown internal influences ; it must be admitted that this 
point is still obscure. The evidence, however, lends support 
to the view that wounding (e.g., tapping) has some effect in 
inducing the alteration in the latex vessel content in trees 
which are predisposed to this condition. In support of this 
view we have the fact that out of a large number of untapped 
- trees systematically examined not one showed development 
of nodules, though this number includes trees up to eleven 
years of age. Out of 2,000 untapped trees eleven years old, 
six yielded nodular structures of about the size of a pea. 
Microscopic examination showed in four trees, where the 
structures were obtained from wound callus, that the struc- 
tures were built up round cavities filled with coagulated latex. 
