FALL OF THE LEAF. 26 1 



any body else, vvho endeavours to explain the physio- 

 locry of vegetables or of animals according to one prhv 

 ciple only, whether it be mechanical or chemical, 

 should entirely fail. To consider the fall of leaves in 

 autumn as a siou^hins, or castinii off diseased or worn 

 out parts, seems so simple and evident, as to be hardly 

 worth insisting upon. Yet I find myself anticipated in 

 this theory by one physiologist only, named Vrolick, 

 cited by Willdenow, in his Principles of Botany^ 

 p. 304, though several learned speculations to uo pur- 

 pose 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 ago remarked to me, that when 

 he had occasion to transplant any tree or shrub v» hilst 

 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 

 decay will generally be extended to the younger more 

 delicate twigs. The exact progress of this decay ma}^ 

 speedily be knov^n, by the leaves of those branches 

 which are irrecoverably dying or dead, remaining 

 firmly attached, so as not to be pulled off without a 

 force sufiicient to brings awav the bark or buds alonif 

 with them : whereas the leaves of parts that have re- 

 ceived no material injury, and ^^•here the vital enei'gy 

 acts with due power, either tail off spontaneously or 



