By Mr. John Robertson. 



181 



progress, by brown or rusty spots appearing on the young 

 shoots, which frequently gum, and die off the same season : 

 should they survive, in the following spring these spots 

 becoming blotches, open, and bleed, the wound expands, and 

 the virus gradually corrodes the adjoining parts, until it encir- 

 cles the branch and destroys it. The cankered part, when 

 cut transversely, exhibits the pith, alburnum, and rind, all 

 tainted by the vitiated sap, which may be traced from the 

 point where it takes its rise, by its discoloured tint, to the 

 wound whence it issues and forms gum ; it is rarely confined 

 to a few parts, but circulates through, and affects the whole 

 system to the extremities. 



Gum is the consequence, either of the plant being propa- 

 gated from a diseased stock ; or, if healthy originally, of the 

 tree being planted in an unsuitable soil or situation ; old gar- 

 dens long worked, exhausted of that freshness so congenial to 

 the Peach, and saturated with acrid and corroding manures, 

 rarely afford healthy Peach trees ; cold clayey ground reten- 

 tive of moisture, and such as have a sour or ferruginous sub- 

 stratum, which chills and cankers the roots, are equally per- 

 nicious to the Peach tree ; on such it generally throws out 

 strong spongy and ill ripened shoots during summer, which 

 possessing a superabundance of crude watery juices, are frost- 

 bitten in winter, and gum and perish the ensuing season. 



Cold raw summers also, in which the mean heat is below 

 the temperature necessary for the Peach tree to elaborate its 

 sap, or enable its vessels to perform their secretions perfectly, 

 always tend to produce gum and canker in fruit trees. 



Disease also proceeds from wounds, or other external inju- 

 ries, of which the Peach tree is susceptible ; in all cases, 



