VARIOUS TYPES OF CAVITIES 163 



cavity is the basal cavity. Basal cavities are 

 caused by decay which enters the trunk at or near 

 the ground, through a wound in the bark, or 

 through a dead root. The only difficulties likely 

 to be met with in handling such a cavity are the 

 thorough excavation of the decay in the roots, 

 if it has worked deeply into them, and the correct 

 handling of the filling in relation to the lower 

 parts of the incision, where complications may be 

 produced by the growth or death of roots. As 

 regards the excavation, every effort must be made 

 to make it complete. If necessary, the opening 

 of the cavity can be enlarged and carried up the 

 trunk, or a new opening can be made, preferably 

 in one of the depressions between the main roots. 

 If the fungus causing the decay is one which de- 

 stroys the heartwood only, it will not be necessary, 

 in case it has worked down into the large roots, 

 to follow it far. The decay is likely to cause 

 less damage in the root than would an incision 

 large enough to make possible its complete re- 

 moval. But as far as the excavation is carried 

 it must be thorough, so that there may be no 

 connection between the remaining decay and the 

 heartwood of the trunk. In making incisions in 

 and about the roots, care must be taken that the 

 free flow of sap is not sacrificed to neatness of 

 outline and ease of filling. In order to " ground " 

 the filling correctly it is usually necessary to dig 



