64 LIFE OF 



morning of September 1st, 1835, 1 observed a shower of honey- 

 dew to descend in innumerable small globules (which become 

 visible when seen in one light) from the leaves of the tree, 

 upon which I found a very large number of aphides, from whose 

 bodies the honey-dew appeared to be ejected with considerable 

 force. I, in consequence, brought home a branch of the tree, 

 which I so placed, that the light, in an otherwise dark room, 

 should shine only upon such branches ; and I then obtained 

 clear evidence that the aphis can discharge its honey with con- 

 siderable force. It is consequently often found in situations at 

 which it could not have arrived by the mere influence of gravi- 

 tation. I suspect this circumstance has led to the belief of the 

 existence of two kinds of honey-dew, one being immediately 

 ejected by plants ; I doubt the existence of more than one 

 kind, for I have often found a minute aphis, by the aid of a lens, 

 in the small globules, apparently emitted by a leaf." 



These specimens may serve to show in some degree how 

 Mr. Knight's mind was always at work, and with what alacrity 

 it seized on whatever contributions of knowledge nature threw 

 in his way, and also the manner in which he extracted out of 

 every-day experience facts which illustrated or confirmed 

 former speculations. 



He carried on a very extensive correspondence, not only with 

 many of the men most distinguished for their attainments in 

 science in Great Britain, but with most of the writers on vege- 

 table physiology and horticulture on the continents of Europe 

 and America. A large collection of interesting letters were 

 preserved by him ; but the limits of this memoir precludes the 

 insertion of more than the few that have been given. He was 

 also a corresponding member of numerous Societies for the en- 

 couragement of horticulture and agriculture in Europe, Ame- 

 rica, and Australia. 



The readiness with which he communicated the results of his 

 investigations, and the practical objects to which they led, 

 caused incessant application to be made to him by horticul- 



