FALL OF THE LEAF. 



[chap. 



difference, the cause of which has not, I think, yet 

 been satisfactorily explained, but into which I will 

 not now enter. 



We have hitherto been considering, for the most 

 part, deciduous trees. It is generally supposed that 

 in autumn the leaves drop off because they die. 

 My impression is that most persons would be very 

 much surprised to hear that this is not altogether 



FiG.^6. — Eucalyptus — Young. 



Fig. jj.— Eucalyptus— Old. 



the case. In fact, however, the separation is a vital 

 process, and, if a bough is killed, the leaves are not 

 thrown off, but remain attached to it. Indeed, the 

 dead leaves not only remain in situ, but they are 

 still firmly attached. Being dead and withered, they 

 give the impression that the least shock would detach 

 them ; on the contrary, however, they will often 

 bear a weight of as much as two pounds without 

 coming off. 



