_The Operation of Grafting_ is performed many ways, though none of them differs from any of the others in the _main principle_, which is that of bringing the under or inner bark of the scion to bear upon the same bark of the stock. The sap of the stock flows upward toward the scion, and it will flow on into the scion, provided it find no interruption. Here, therefore, is the nicety--to fit those two barks so closely, the one upon the other, that the sap shall proceed onward into the scion, just as it would have done into the amputated branch, causing the scion to supplant the branch. I shall only mention and illustrate two modes of grafting, viz., _tongue-grafting_ and _cleft-grafting_. These two it is necessary for me to speak of separately, and thoroughly to describe, for they are not both of them applicable in all cases; the former being used in grafting on small-sized stocks and small branches of trees, and the latter on large stocks and large branches. [Illustration: TONGUE-GRAFTING.--(FIG. 58.)] _Tongue-Grafting._--Suppose you have your stock of the proper age for grafting, you cut it off at three or four inches from the ground, and with a very _sharp, straight, and narrow-bladed grafting-knife_, cut a thin strip of bark and wood upward, from about two inches below your already shortened stock. Make this cut at one pull of the knife, inserting the edge rather horizontally, and when it has gone through the bark and into the wood a little short of the middle, pull straight upward, (2, _a, b_;) then at rather less than half way down this cut, and with the blade of your knife across the cut, and downward, cut a very _thin tongue_ of not more than three eighths of an inch long, (2, _c_.) Proceed nearly in the same way with the bottom part of the scion; cut first a narrow strip of wood and bark out, but not putting the knife in horizontally, as you have done with regard to the stock, (at 2, _a_,) nor bringing it out straight to the end, to make a shoulder or angle, as you have done at (2, _a b_;) but make a sloping cut (1, _a b_,) of about the same length as the cut in the stock, or rather a little less if anything; then make a tongue (1, _c_) to correspond with that of the stock, but recollect that this must be cut _upward_ instead of _downward_; then place the scion upon the stock, inserting the tongue of the scion into the tongue of the stock. Bring the four edges of bark, that is, the two edges of the cut in the top of the stock, and the two corresponding edges of the cut in the bottom of the scion, to meet precisely; or, if the scion be, in diameter, a smaller piece of wood than the stock, so that its two edges of bark can not both meet those of the stock, then let only one meet, but be sure that one meets precisely. But observe, that this can never be unless the first cut in the stock and that in the scion (2, _a b_,) and (1, _a b_,) be as even as a die, and performed with a knife scarcely less sharp than a razor.