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 to 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 been 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 is 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 their force since.
Weeping-willows, bread-fruits, bananas, sugar-cane, tiger-lilies, Jerusalem
artichokes, and the like, have been propagated for a long while in this
way, without evident decadence. Moreover, the analogy upon which his
hypothesis is founded will not hold. Whether or not one adopts the present
writer's conception, that individuality is not actually reached or
maintained in the vegetable world, it is clear enough that a common plant
or tree is not an individual in the sense that a horse or man, or any one
of the higher animals, is--that it is an individual only in the sense that
a branching zoophyte or mass of coral is. Solvitur crescendo: the tree and
the branch equally demonstrate that they are not individuals, by being
divided with impunity and advantage, with no loss of life, but much
increase. It looks odd enough to see a writer like Mr. Sisley reproducing
the old hypothesis in so bare a form as this: "I am prepared to maintain
that varieties are individuals, and that as they are born they must die,
like other individuals . . . We know that oaks, Sequoias, and other trees,
live several centuries, but how many we do not exactly know. But that they
must die, no one in his senses will dispute." Now, what people in their
senses do dispute is, not that the tree will die, but that other trees,
established from its cuttings, will die with it.