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healing of the wound is performed by the activity of the cambium. 
As the growth of the cambium proceeds a soft cushion or “callus ” 
is formed-, looking like a thickened lip to each margin of the cut. 
The “ callus ” growth proceed over the surface of the exposed wood 
and, eventually, by the meeting and fusion of the lips the wound is 
healed. The exposed surface of wood becomes covered with a layer 
of what is known as “ wound wood,” in which the vessels are short 
and irregularly arranged. This “ wound wood ” is produced in 
excess of the amount developed by the surrounding parts of the 
cambium with the result that the surface of the back overlying the 
wood which was originally exposed is raised into a bump. 
The surface irregularities of this kind are, therefore, easily 
avoided by obtaining from wounding the wood in tapping. 
The ultimate fate of such structures is that they eventually 
become obliterated by the further production of normal wood by the 
cambium at those points. 
A good example of the origin of these structures is given by 
Petch, in which a tree had been tapped on the system of separate 
Vs which had penetrated to the wood; on removing the bark the 
wood was found to b? raised in Vs, each of which corresponded with 
a tapping cut. 
THE CHIEF DISEASES OF PARA RUBBER \H 
IV1ALAYA AND CEYLON. 
The works of M. George Vernet, on Rubber, are always worth 
reading, and his recent publication Sur les principales Maladies de 
1’Hevea dans ;la peninsule Malaise a Java et a Ceylon, is no excep- 
tion. He describes and illustrates with photographs the chief pests 
which attack our Heveas. They are the following : — 
i. White root fungus (Champignon blanc des racines.) This 
is known by its fine white filaments which form characteristic 
strands. This is the mycelium which we have always believed to be 
that of Fomes semitostus. M. Vernet discusses the question at some 
length. Doubt seems to have been thrown on the identification 
chiefly on account of the fructification of Fomes not having always 
been seen on roots or trees attacked by the white fungus. I have not 
the slightest doubt myself on the subject. Every tree and every root of 
sufficient size bearing the white fungus will here, especially in wet 
weather, produce the characteristic brackets of Fomes. Where the 
ground is thoroughly infected with the white fungu-, Fomes is very 
abundant and no other fungus usually visible. 
“ Let us not forget,” says M. Vernet “ that one only meets with 
Fomes semitostus on dead wood not on living organs.” It is true that 
by the time the fructification is developed the part of the tree that 
bears it is dead, but it does occur on trees not yet dead and only 
affected as far as the fungus has gone. There are many of the bracket 
