112 A. Gray—Do varieties wear out, or tend to wear out? 
earliest times ; and that Golden Pippins, St. Michael pears, and 
others said to have run out, were still to be had in good condi- 
on. 
Coming down to the present year, a glance through the pro- 
ceedings of pomological societies, and the debates of farmers’ 
clubs, brings out the sume difference of opinion. The testimony 
is nearly equally divided. Perhaps the larger number speak of 
the deterioration and failure of particular old sorts; but when 
the question turns on “wearing out,” the positive evidence of 
vigorous trees and sound fruits is most telling. A little positive 
testimony outweighs a good deal of negative. This cannot read- 
from whatever cause. This consideration has an importa 
bearing upon the final question, are old varieties of this kind 
on the way to die out on account of their age or any inherent 
limit of vitality ? 
Here, again, Mr. Knight took an extreme view. In his essay 
in the Philosophical Transactions, published in the year 1810, 
he propounded the theory, not merely of a natural limit © 
varieties from grafts and cuttings, but even that they would not 
survive the natural term of the life of the seedling trees from 
which they were originally taken. Whatever may have bee? 
his view of the natural term of the life of a tree, and of a cutting 
being merely a part of the individual that produced it, there 8 
no doubt that he laid himself open to the effective replies which 
were made from all sides at the time, and have lost none of 
