CH. VIII.] THE DISEASES OF PIANTS. 291 



danger of the roots striking into the worse pasturage 

 of the subsoil. On this point, the experience of Mr. 

 W. Nichol, the gardener at Newick Place, in Sussex, 

 agrees Anth my own. He says that the canker 

 may he avoided in most instances by paying proper 

 attention to the soil in which the tree is planted. 

 Canker, he thinks, will seldom occur if the surface- 

 soil is good, for in that case the roots aatII never 

 descend into the prejudicial subsoil, but spread out 

 their radicles near the surface, where they find food 

 most abundant. If this is not kept up, the roots 

 descend into the obnoxious substratum, and the 

 disease assuredly follows^. 



It remains for me to detail the course of treat- 

 ment that I have always found successful in effecting 

 a cure in any variety not decrepit from age, if the 

 canker has not spread to the roots. 



Having completely headed down, if the canker is 

 generally prevdent, or duly thinned the branches, 

 entirely removed every small one that is in the 

 least degree diseased, and cut away the decayed 

 parts of the larger, so as not to leave a single speck 

 of the decayed wood, I cover over the sm'face of 

 each wound with a mixture, whilst in a melted state, 

 of equal parts tar and rosin, applying it vdth a 



* Baxter's Library of Agric. and Hortic. Knowledge, 3rd 

 Edit. 22. 



u2 



