SEASON FOR PRUNING. 59 



recommended from time immemorial is the oint- 

 ment of St. Fiacre, a mixture of loam and cow 

 dung. Various preparations, too, used in grafting, 

 and having rosin, wax, and grease, as their basis, have 

 at different times been very generally recommended 

 for this purpose. These preparations are expensive ; 

 and, as they must be applied hot, it is not prac- 

 ticable to use them on a large scale. Their use, too, 

 is attended with serious difficultieSc As the new 

 growth of wood spreads over the wound, these thick 

 coatings are either broken or pushed aside bodily, ac- 

 cording to the power of resistance of the material 

 used ; and the wood is again exposed and a safe 

 retreat for injurious insects prepared. 



One coat of coal-tar is sufficient for wounds of or- 

 dinary size ; but, when they are exceptionally large, a 

 second coat may, after a few years, be well applied. 

 In warm countries, like the south of France, the great 

 heat of summer renders coal-tar so liquid that it is 

 often impossible to properly treat wounds made at 

 that season. In such cases another coat should be 

 applied during the following winter. 



Effects of Coal-tar on the Elm, The effect of coal- 

 tar on the Elm is not always as satisfactory as upon 

 other forest trees, such as the Oak, Ash, Sycamore, 

 Birch, Maple, etc. The application of a coat of coal- 

 tar on all of these gives at once to the wound a hard 

 firm surface ; on the Elm, however, it does not always 

 adhere firmly, owing to the formation on the surface 

 of the wound of the water blisters common to this 



