REPAIR OF SHADE TREES 161 



done in spring, by the use of dormant shoots or twigs of 

 the previous year's growth somewhat longer than the bare 

 place, affixed perpendicularly under the freshly trimmed 

 edges of the bark to bridge the wound. The ends of the 

 twigs are trimmed wedge shape, and these sharp ends are 

 inserted between bark and wood, beneath slits in the bark 

 above and below the wound. When properly placed, they 

 form a bridge through which the sap may flow. To hold 

 the bridge in place, a cloth bandage should be tied around 

 each edge of the bark. To prevent drying, the ends of the 

 bridging twigs should be coated with melted grafting wax. 

 This wax may be made of four parts of resin, two parts of 

 beeswax and one part of tallow, melted together and 

 worked with greased hands, in cold water, until it becomes 

 grainy. Success with bridge grafting depends upon close 

 contact of fresh cambium layers of scion and stock at both 

 ends, with immediate protection from further evapora- 

 tion by thorough and careful waxing. 



Cavities offer serious problems in the life of a tree and 

 require careful treatment. Minor cavities may be cared 

 for by the layman, without previous experience, if simple 

 rules are closely followed, but in the case of a large one it is 

 unwise for the work to be undertaken by any but the 

 technically trained expert. 



One of the commonest causes of decayed cavities is 

 the protruding stub left from careless pruning. Unless 

 the limb has been cut without leaving a stub, rot will start 

 which, sooner or later, will spread its decay into the trunk. 

 Similar results come from neglected surface wounds. In 

 the course of time troubles thus started imperil the life 

 of the tree. 



In the treatment of cavities it is most important that 



no trace of dead or diseased wood be allowed to remain. 



The basic principle is to make sure that all decay is 

 ii 



