io6 DISEASES OF CROP-PLANTS 



exposed wood until the healing process has time to complete 

 itself. What is desired is a durable coating which does not 

 readily crack, which has no ill effects on bark or callus, and 

 preferably is to some extent antiseptic. Coal tar sometimes 

 proves definitely objectionable on the second count ; the differ- 

 ences of experience in this matter probably arise from differ- 

 ences in composition of the material used. Resin-petroleum, 

 prepared by dissolving 3 parts of resin in one part of warm crude 

 petroleum, has been recommended. The simplest treatment, 

 which in many cases has proved quite satisfactory, is the applica- 

 tion at intervals of coats of white lead paint. 



The writer has experimented with a paint which gives better 

 results where protection is decidedly needed, as on soft and 

 spongy woods, than any other which has been tried. It is 

 prepared by heating over a slow fire until smooth 20 oz. of boiled 

 linseed oil and 12 oz. of Barbados manjak, a hard bright asphalt. 

 Probably a preparation of manjak and crude petroleum would 

 also be satisfactory. 



On young and vigorous trees with durable wood, provided 

 wounds are shaped to cover easily, and provided the conditions 

 of shade and moisture are not extreme, there is commonly no 

 need of any artificial protection, though in some localities con- 

 sideration has further to be given to the habit of some species 

 of ants in occupying exposed wood, especially Cremastogaster 

 sp., the acrobat ant, which seems to attack the cambium and 

 seriously delays the restoration of the bark. 



