RUBBER (HEVEA) DISEAS /d 
the locally affected area or a flow to the injured tissues from the sur- 
rounding parte, with subsequent coagulation in the latex tubes. This 
is analogous to the pathological effects of fungi which break down 
the resin system of coniferous tree-, resulting in an impregnation of 
the wood and bark. The exudation of latex without the agency of 
wounds by fungi and animals is more difficult of explanation. It is 
not analogous to the dissolution of substances in the cortex of various 
gum-producing trees, since an entirely different process and a differ- 
ent set of structures are involved. The formation of resin blisters 
in the parenchymatous cambial tissues of many conifers is probably 
the neare.-t approach to the conditions found in Hevea. 
Long streaks of black coagulated latex have been observed on the 
smooth white bark of Hevea. If the point of exit is examined by 
shaving down the cortex a small discolored spot may be exp< 
but the surrounding tissues and the cambium beneath appear t- 
perfectly healthy. It is possible to conceive of an excessive turgidity 
of the latex system on young green stems under favorable grox 
conditions, resulting in a rupture of the epidermis and flow of la 
Short splits in green twigs from which latex has exuded were ob- 
served on Hevea and also on Ficus. 
It would be difficult to decide just what part insects and bird- 
play among such phenomena. It has been pointed out that latex 
sometimes exudes from abnormally formed lenticels on young twigs. 
This may be considered a natural response to a diseased condition. 
It is unlikely that latex will flow from the cortex on mature parts 
of the tree without the intervention of wounds of some kind. The 
report that Hevea trees in Brazil and Bolivia have been known to 
burst, causing the formation of large masses of coagulated rubber 
at the wounds, is probably confused with similar phenomena result- 
ing from lightning wounds or abrasions from falling objects. 
Certain undetermined insects were observed to puncture the delicate 
green epidermis of young fruits, causing black spots and streaks 
to appear on the surface. Other forms of latex exudations seem 
to emanate from the activities of the numerous tree cuts. 
RUBBER PADS 
Sometimes the latex, instead of flowing outwardly, accumulates 
and coagulates in pockets between the cortex and the wood, forming 
lenticular pads. These were found around old tapping cuts, on 
surface roots where the cortex had been bruised from treading. 
and in old cankers of unknown origin at the base of untapped tree-. 
Pads formed beneath healthy though slightly roughened bark were 
found in a few cases only (PI. XIV. B). A blow on the slightly 
raised areas caused a rebound of the ax and resulted in their dis- 
covery. The surface of the wood beneath was discolored, but other- 
wise the surrounding tissues were healthy. The rubber of all these 
pads was clear and of good quality. 
A very curious pad formation is found on old tapping cuts of old 
trees in damp situation-. It appears that the coagulated latex in 
these wounds is infested with an insect. Evidently the flow is 
stimulated after the infestation: otherwise the size of some of these 
pads, known as black sera]) or oxidized rubber, would be difficult 
to explain. They are frequently found as large as a man's list and 
