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something congenial to the fruits in these. The grafts grew tolerably, and equally in all; but there 
was a want of hardness and elasticity in the wood, and at the end of three or four years all began to 
canker. This disease is always found in those varieties which have been long in cultivation; and in 
these it annually becomes more destructive, and evidently arises from the age of the variety; but it 
often appears to be hereditary. A gravelly or wet soil, a cold preceding summer, or a high exposed 
situation, add much to its virulence. It is most fatal to young free-growing trees of old varieties; 
and even the strong shoots of these will be totally destroyed by it, when the old trees growing in the 
same orchard, and from which the grafts had been taken, were nearly free from the disease. The 
young stocks, by affording the grafts a preternatural abundance of nourishment, seem to bring on 
the disease; and transplanting, or a heavy crop of fruit, which check the growth of the tree, diminish 
its disposition to canker. In middle-aged trees of very old varieties a succession of young shoots is 
annually produced by the vigour of the stock, and destroyed again in the succeeding winter: the 
quantity of fruit these produce is in consequence very small. In this disease something more than 
a mere extinction of vegetable life appears to take place. The internal bark bears marks of some¬ 
thing similar to erosion; and this is probably the original seat of the disease, though the wood of the 
annual shoots is soon tinged to the centre. The canker does not appear to be ever a primary or 
merely local disease, but to arise from the morbid habit of the plant, and to be incurable by any 
topical application. 
Being after much unsuccessful experience satisfied, that those varieties of the Apple, of which the 
original trees had long perished from old age, could not be made to grow; Mr. Knight suspected, 
that grafts taken from very young seedling trees, not yet in a bearing state, could not by any means 
be made to produce fruit. Having taken cuttings from some of these of two years old, he inserted 
them in stocks of twenty, which had already produced fruit. He afterwards frequently transplanted, 
and took every means in his power to make them produce blossoms; but though they grew in rich 
ground, which probably tended to accelerate their maturity, he did not succeed till the seedling trees 
were twelve years old, the age at which they usually produce fruit; and then other grafts of the 
same kind, which had been inserted but three years before, readily blossomed. Other cuttings were 
inserted in very old stocks, which were regrafted; these grew with excessive vigour, but did not pro¬ 
duce blossoms so soon as the others. 
From the result of these experiments, and from the general failure of every attempt to propagate 
every old variety of the Apple, Mr. Knight thinks himself justified in the conclusion, that all Apples, 
however propagated from the same stock, partake in some degree of the same life, and will attend 
it in the habits of their youth, their maturity and decay; though they will not be any way affected 
by any incidental injuries the parent tree may sustain, after they are detached from it. The roots 
however, and the trunk adjoining them, appear to possess in all trees a greater degree of durability 
than the bearing branches, having a power of producing new ones, when the old have been destroyed 
by accident, or even by old age: and grafts taken from scions, which have sprung out of the 
trunks of old ungrafted Apple and Pear trees, will grow with much greater luxuriance than those 
taken at the same time from the extremities of the bearing branches. The former in their growth 
assume the appearance of young seedling stocks, and the shoots of the Pear are, like those, covered 
with thorns. Those propagated from the bearing branches frequently produce fruit the second year, 
but the others remain long unproductive. It appears therefore extremely probable, that such trees as 
the Walnut and Mulberry, which do not produce fruit in less than twenty years, might be rendered 
fruitful in one third of that time, by being grafted with cuttings taken from the productive branches 
of an old tree. 
Since then the valuable varieties of the Apple and Pear cannot be continued for ever, till new 
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