THOMAS ANDREW KNIGHT. 
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to Mr. Knight, and he had the great pleasure of being introduced to many of the most distinguished 
men in science and literature. Sir Joseph Banks never afterwards lost an opportunity of assisting 
Mr. Knight, by procuring information for him, or by giving him that friendly and courteous advice, 
which was of still greater value. 
Mr. Knights first communication was made to the Royal Society, April 30th, 1795 ; through 
the influence, no doubt, of his friend the President. It was that famous paper, “ Observations on the 
Grafting of Trees ” in which Mr. Knight maintained the doctrine that there was no renewal of vitality 
in the process of grafting, but that the scion carried with it the debility of the tree from which it was 
taken. He advanced the same opinion in his “ Treatise on the Culture of the Apple and Pear , and 
of the Manufacture of Cider and Perry P published in 1797 ; and it seemed to result, so naturally, 
from his observations, and from the series of ingenious experiments he carried out; whilst, at the 
same time, it seemed to explain so well the cankered and diseased state of most of the trees of the 
old varieties of cider apples, in the orchards of Herefordshire, that it was at once generally 
received. It was an old theory revived, but was so well put forward that the merit of an actual 
discovery was awarded to Mr. Knight by common consent. It can, however, easily be shown, that 
the belief that a graft would not live longer than the tree from which it was taken was general 
from a very early period, if not from the time when grafting was first practised. This might be 
proved by reference to the gardening books of the age, but it is scarcely necessary to do so 
since they are quite obsolete. 
Even Pliny contrasts the short duration of the apple with the productiveness of pears and 
other fruit trees when grown old. He says :— 
“ Celerrime vero senescit, et in senecta deteriorem fructum gignit malus. Namque et 
minora poma proveniunt et vermiculis obnoxia.” Hist. Nat. xvi, 27. 
“ Apple trees soon grow old, and in their old age bear inferior fruit. The apples produced 
are not only smaller, but apt to be grubby.” 
The difficulty of propagating by grafts, from old and cankered trees, was well known in 
all orchards. The world was prepared to believe, that “ canker” would always prevent the old 
varieties from being prolonged in this, or in any other way ; and when Mr. Knight laid down the 
law so precisely, and seemingly proved it by his experiments so conclusively, that “ Vegetable like 
Animal life has its fixed periods of duration,'’ and that the different varieties of apple trees thus 
died out naturally, the opinion was universally received without hesitation. 
Mr. Knight was right in attributing “ canker” in the graft, to the age and debility of the 
individual tree, from which it was taken, but he v/as wrong in supposing it due to the age of the 
variety of apple. His theory was, that all the trees of any given variety were really nothing more 
than separate and isolated branches of one tree; whereas every bud in essence is a new tree with a 
new life. Mr. Knight’s experiments had indeed proved that “ the existence of a variety of fruit 
trees may be protracted beyond the natural terms of the original seedling plant by grafting, or by 
unusually favourable circumstances of soil and situation.” Had he carried out these experiments 
further he would have hesitated to state as he then does, “ that there is a period, beyond which 
the debility incident to old age cannot be stimulated.” This is now believed not to be correct. 
“ Canker” is due to debility from any cause. It may arise from the age of the tree itself; 
