THE FRUIT TREES OF AMERICA. 
419 
we desire to impart hardiness to a tender 
fruit, we must undertake a cross between it 
and a much hardier sort ; if we seek greater 
beauty of colour, or vigour of growth, we 
must insure these qualities by selecting one 
parent having such quality strongly marked." 
—P. 11. 
The volume thus opened presents us next 
with all the modes of grafting, budding, lay- 
ering, and raising from cuttings, none of 
which is new on this side of the Atlantic. 
There are occasionally some appropriate ob- 
servations, which are both interesting and 
instructive. As an instance, we give some 
remarks on the influence of the stock and 
graft, which is curiously described by De 
Candolle. 
" The well known fact that we may have a 
hundred different varieties of pear upon the 
same tree, each of which produces its fruit of 
the proper form, colour, and quality ; and 
that we may have, at least for a time, several 
distinct, though nearly related species upon 
one stock, as the Peach, Apricot, Nectarine, 
and Plum, prove very conclusively the power 
of every grafted or budded branch, however 
.small, in preserving its identity. To explain 
this, it is only necessary to recall to mind 
that the ascending sap, which is furnished by 
the root or stock, is nearly a simple fluid ; 
that the leaves digest and modify this sap, 
forming a proper juice, which re-descends in 
the inner bark, and that thus every bud and 
leaf upon a branch maintains its individuality 
by preparing its own proper nourishment, or 
organizing matter, out of that general aliment, 
the sap. Indeed, according to De Candolle, 
each separate cellule of the inner bark has 
this power of preparing its food according to 
its nature ; in proof of which, a striking ex- 
periment has been tried by grafting rings of 
bark, of different allied species, one above 
another on the same tree without allowing 
any buds to grow upon them. On cutting 
down and examining this tree, it was found 
that under each ring of bark was deposited 
the proper wood of its species, thus clearly 
proving the power of the bark in preserving 
its identity, even without leaves. 
" On the other hand, though the stock in- 
creases in size by the woody matter received 
in the descending sap from the graft, yet as 
this descends through the inner bark of the 
stock, it is elaborated by, and receives its 
character from the latter ; so that, after a tree 
has been grafted fifty years, a shoot which 
springs out from its trunk below the place of 
union, will always be found to bear the origi- 
nal wild fruit, and not to have been in the 
least affected by the graft. 
" But, whilst grafting never effects any al- 
teration in the identity of the variety or 
species of fruit, still it is not to be denied that 
the stock does exert certain influences over 
the habits- of the graft. The most important 
of these are dwarfing, inducing fruitfulness, 
' and adapting the graft to the soil or climate. 
" Thus every one knows that the slower 
habit of growth in the Quince stock, is shared 
by the Pear grafted upon it, which becomes 
a dwarf; as does also the Apple when worked 
on the Paradise stock, and, in some degree, 
the Peach on the Plum. The want of entire 
similarity of structure between the stock and 
graft, confines the growth of the latter, and 
changes it, in the case of the Pear, from a 
lofty tree to a shrub of eight or ten feet in 
height. The effect of this difference of struc- 
ture is very apparent, when the Peach is 
grafted on the Plum, in the greater size of the 
trunk above, as compared with that below the 
graft; a fact which seems to arise from the 
obstruction which the descending sap of the 
graft finds in its course through the bark of 
the stock."— Pp. 24, 25. 
Knight accounts for the disposition of the 
plants grafted on these dwarfing stocks to bear 
earlier, by attributing it to the obstruction 
formed to the descending sap. This is a very 
pretty theory, but nothing can be more erro- 
neous; were it not so, how is it that root- 
pruning produces the same effect ? nobody can 
say there is any obstruction to the descending 
sap in trees so treated. The fact is, half the 
theorists make the descending sap a wonderful 
agent, while their proofs of its agency, or 
otherwise, are lame and impotent. The true 
secret is, that there is a less supply of sap as 
compared with the work it has to perform, 
and that diminished supply is easier and bet- 
ter elaborated, and prepared for the production 
of fruit. Let a tree be as vigorous as it 
may, it will keep growing for years without 
bearing ; indeed it will continue to increase 
in size to a vast extent, so long as the supply 
of sap is superabundant ; but when it has 
attained a growth that requires all the supply, 
and there is no longer too much for the size 
of the head, it will bear abundantly. On the 
other hand, if such a tree be root-pruned at a 
much earlier period, it will bear, not because 
there is any obstruction to the descending sap, 
but because the supply of sap is lessened, and 
the tree is starved into prematurity. In the 
same way will the starving of a plant throw it 
earlier into bloom ; the descending sap has no 
more to do with the bearing or blooming of a 
plant or fruit tree, than it has with the man in 
the moon. We notice that the author men- 
tions also the fact, well established, it is true, 
but not half enough attended to, that the stock 
upon which anything is grafted, should be 
adapted to the soil. Thus he says, the Peach, 
which on its own roots will hardly live on 
h h2 
