60 BULLETIX 1380, IT. S. DEPARTMENT OF AGRICULTURE 
stantly filled with rain water and vegetable debris or may 
support epiphytic plants. In two such cavities encountered it was 
found that the cortex had broken down, presumably under the com- 
bined influence of poisonous substances and fungi. The wood was 
decayed around the sides of the cavity. The sporophores of Poly- 
porus zonal is were present in one instance and those of Fomes horno- 
dermus in the other. 
The development of three main branches sometimes occurs in 
Hevea, resulting in the formation of a dee]) crotch. If the branches 
are inclined to the vertical, as frequently happens, there may be an 
accumulation of materials, such as dirt in the form of dust washed 
down from above, dead nark scales, and the seeds of epiphytic 
plants. This accumulation may result in damage to the tree, in 
that it promotes the development of fungi which may find entrance 
at this point, especially if the interference of the branches has re- 
sulted in a deep crack. The swaying of the branches by the wind 
may open the crack to the wood, with serious consequences. A crotch 
of this kind was opened with an ax, and the crack was found to 
extend to the wood. The wood was discolored and infected with. 
an undeterminable fungus. This condition may occur, but to a 
much less extent, in trees with only two main branches. It is the 
practice in the East to clean up these forks, since the condition is 
believed to facilitate the entrance of fungi. In this connection 
Akers, writing of canker on Hevea in the Amazon Valley, states 
that "it is found generally at the junction of the main lateral 
branches with the trunk, where a lodgment of rain water has taken 
place. The effect is to rot both branches and stem until the tree 
becomes exhausted and die-.'* Xo such serious condition was en- 
countered during the present investigation, but under plantation 
conditions it would be well periodically to clean and sterilize the 
forks. 
One of the most common natural wounds occurring on Hevea in 
the forest and in closely planted estates is the suppression of lower 
branches by shade. The loss of light due to the increase of the crown 
above causes the lower branches to become greatly reduced in vigor. 
which ultimately results in death. This process is usually hastened 
by the action of numerous semiparasitic and saprophytic fungi. 
When the branch is decomposed it falls from the tree, leaving a pro- 
jecting stub, or, if the decomposition is very complete, a hole in the 
tree. In either case wound fungi or those which aided in the de- 
composition of the branch advance within the knot and attack the 
wood of the trunk. The death of the lower branches may be ex- 
pected when their twigs and leaves are killed by parasitic fungi. 
Species of fungi which have been collected on dead suppressed 
branches causing a decay within the knot are numerous. The most 
common are Trametes hydnoides, T. rigida, T. cormigata, Lenzltes 
striata, Odontia sp., Polystictus atypus, Stereum papyrinwm*, 8. 
iimbrinin/), Schizophylhim commune, and Cortic'nim sp. 
The hollowing out of the knot by these fungi prevents the even 
formation of an occluding callus, which usually in such cases curves 
inwardly, delaying the complete closing of the wound. Hollow 
knots may reduce the mechanical strength of the tree and cause its 
overthrow by wind. 
