342 FALL OF THE LEAtf 



casting ofif diseased or worn out parts, seems 

 so simple and evident, as to be hardly worth 

 insisting upon. Yet I find myself antici- 

 pated in this theory by one physiologist only, 

 named Vrolick, cited by Willdenow, in his 

 Principles of Botany, p» 304, though several 

 learned speculations to no purpose are extant 

 on the subject. It is but just, however, that 

 I should relate what led me to consider the 

 matter with any attention. My observing 

 friend Mr. Fairbairn of Chelsea garden long 

 aoo remarked to me, that when he had occa- 

 sion to transplant any tree or shrub whilst 

 in leaf, he could soon judge of its success by 

 the ease with which its leaves were detached. 

 The consequence of such treatment is more 

 or less injury to the health of the plant, as 

 will first appear by the drooping of the leaves, 

 most of which will probably die, and the de- 

 cay will generally be extended to the younger 

 more delicate twigs. The exact progress of 

 this decay may speedily be known, by the 

 leaves of those branches which are irrecover- 

 ably djing or dead, remaining firmly at- 

 tached, so as not to be p<nicd ofT without a 

 force sufficient to bring away the bark or 



