Transactions of the Horticultural Society. 69 



experimenting on it. His opinion is known to be in fa- 

 vor of the idea, that varieties are formed for a limited period 

 of duration only ; but he has brought forward nothing to dis- 

 prove, that if a variety be renovated by frequent propagation, it 

 may not last and retain all its properties for ever. For ex- 

 ample, suppose the golden pippin to be at present in full per- 

 fection as a variety of apple ; take healthy scions from a tree, 

 and graft them on healthy stocks ; the produce of these scions 

 will be of the same quality as those of the parent tree ; while 

 this offspring tree is in full vigour, take scions from it, and 

 graft them on healthy stocks as before ; the same quality of 

 fruit in an equal degree of perfection will be produced. Now, 

 the question is, whether this process might not go on for an 

 unlimited period, care always being taken to take off the scions 

 for the purpose of renovation, before the tree they were taken 

 from, became diseased or decayed ? At the same time, it is an 

 unquestionable fact, that the varieties of some species of fruit 

 which have been long cultivated, are now degenerated ; but 

 whether this is the consequence of neglect of timely renova- 

 tion, or whether it arises from the constitution of the variety, 

 is very uncertain, and not likely to be soon determined from 

 facts. That some varieties are constitutionally more apt to 

 degenerate than others, is within the limits of every gardener's 

 experience ; and equally so the counteracting influence of fre- 

 quent renovation. From the results of Mr. Knight's experi- 

 ence, he infers " that the debility and diseases of old varieties 

 arise from the want of a properly prepared circulating fluid ; 

 and that when such is given by efficient foliage,, the bark of 

 the most debilitated variety possesses: the power to occasion 

 the necessary secretions to take place, and the alburnum is en- 

 abled to execute all its offices." The foliage could never be 

 otherwise than efficient, or the bark than healthy under a sys- 

 tem of frequent renovation ; and therefore it is difficult to avoid 

 concluding, that such a system would keep up any variety in 

 perfection for ever. It certainly seems to do so with some 

 varieties of plants commonly cultivated ; as willows, poplars, 

 vines, figs, &c, which are certainly -not often re-originated from 

 seed. But this subject can hardly be treated with advantage 

 without considering together the whole that has been advanced 

 on it ; and we shall leave off, only observing, that even the 

 conjectures of a philosopher who has studied the subject for so 

 long a period as Mr. Knight, deserve the utmost respect. In 

 this paper, these conjectures are much more consonant with 

 common experience, than in several of the essays which 

 appeared in the Philosophical Transactions. 



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