CONTRIBUTIONS FROM THE WISLEY LABORATORY. m 



but that the leaves are infected "directly from the exterior, probably by 

 spores which have wintered hidden in crevices of the bark &c. 



Outbreaks of curl on outdoor peaches and nectarines are generally 

 attributed to various inanimate causes, such as unsuitable or unwhole- 

 some soil, * climatic and weather conditions, f and the last-named 



factors are of importance from the fact that cases of leaf curl occur 

 rarely under glass where the conditions are more or less under control ; 

 and varietal factors. In Belgium considerable attention has been 



* Gardeners' Chronicle, May 21, 1842, p. 333. 



t Pierce, Peach Leaf Curl, its Nature and Treatment, Washington, 1900 ; 

 G. Arnaud in Revue de Phyt. ; Gardeners' Chronicle, May 28, 1842, p. 349 &c. 



