68 BULLETIN 1380, U. " S. DEPARTMENT OF AGRICULTURE 
where the excavation would involve too great an area of the surface 
of the trunk or the heartwood. The wood of Hevea is not very strong, 
especially in young trees, and a large excavation would cause the 
tree to be broken off by the wind, either in the case of cavities at the 
base of the tree or higher on the trunk. A greater measure of suc- 
cess would attend the operation at the base of the trunk, owing to 
the greater mechanical strength at that point. 
A first requisite in treating wounds by this method is a knowledge 
of the fungi concerned. Obviously it would be useless to attempt 
to prevent in this way the spread of the decay caused by a parasitic 
wood-destroying fungus. The mycelium is usually so far in advance 
of the visible decay that it is impracticable to judge its extent in 
the roots and root collar; also at the time the decay becomes appar- 
ent the tree may already be doomed. Polyporus lignosus, Poria 
vincta, and other parasitic fungi fall in this class. The activities of 
wood-destroying fungi that attack only the dead wood of wounds or 
enter the heartwood by this means may be successfully combated but 
only when the operation is properly performed. The operation will 
not be a success unless all the diseased wood is removed. The decay 
will continue behind the filling if all the infected wood is not 
taken out. After the diseased wood is removed the raw surface 
should be thoroughly treated with a disinfectant. When the surface 
is dry it should be painted with asphaltum and the cavity filled. 
The filling should not extend beyond the cambium. This will per- 
mit the callus to form evenly over the surface and hold it in place. 
If the healing is complete the surface of the trunk will be uniform. 
In some cases it may be desirable not to fill the cavity after thorough 
disinfection and application of asphaltum. If the cavity is so made 
that water will not collect in it, it will soon dry out under such 
treatment, and decay or reinfection will be prevented. Cavities 
treated in this way. however, do not have a finished appearance. 
There is also the less of tapping surface, since it requires a long 
period for such cavities to occlude. 
PREVENTITIOUS AND ADVENTITIOUS NODULE STRUCTURES 
The practice of wounding the tree to collect the latex promotes 
the formation of other forms of abnormalities which are much less 
conspicuous than the callous nodules. Before these abnormalities 
are discussed it is well to consider certain regenerative phenomena 
which may be intensified by this form of tapping, by injury to 
the crown by various agents, or that may be a natural response on 
the part of the tree for self-maintenance. 
The normal buds of a young tree may be distinguished accord- 
ing to their position as acropital and axillary, as they are developed 
at the end of the new shoots or in the axils of the leaves. With re- 
gard to their manner and mode of development, they may be dis- 
tinguished as shoot forming and as dormant or prevent itious buds. 
The first are characterized by the vigorous production of shoots 
which normally branch and again produce acropital and axillary 
buds. These shoots usually stand at an acute angle to the parent 
stem. Although several lateral or axillary buds may be produced, 
only a limited number develop into shoots. The others remain 
