Marriage, according to the paradigm of grafting, solves a lot of what appear to be riddles in the minds of modern people. It gives a legitimate, visible, tactile comparison that anyone with the mind of a ten year-old can understand, and possibly even perform…the grafting, if not the marriage. (This does raise an interesting point though about what sort of consent and is necessary. Maybe next time. I know everyone loves it when I talk about less-than consensual marriage.)
One of the noticeable things about grafting is that what will become one plant is, at first, only two small parts of what were much larger plants. There is a lot of cutting. Obviously the location of the grafts are cut. The rootstock is usually cut way down to accept the scion–the branch portion. The scion is cut from the midst of its plant; above and below are removed. Sometimes the leaves are cut from the stock and the scion, but not always.
In the case of grapevines, the stock is also sliced in a location away from the actual graft cuts so that it bleeds. Otherwise the pressure of the sap in the stock will dislodge the scion.
The graft has to be bound together for a season so that it will take.
When the case happens where there are several shoots from the budding graft, it is a good practice to cut off the latter shoots and give the strength of the resources to the first large bud. Obviously, the law of resources requires that any malformed or diseased buds be cut off from the new plant.
Once the graft has taken, there is no way to cut cleanly excise what was grafted in. There will be changes. Even before the cambiums of the stock and the scion fuse, there must be an infusion of sap from the stock to the scion. It cannot be extracted. The scion portion of the graft can of course be cut off, and perhaps even grafted onto another rootstock, but it will not be the same scion that was originally grafted. Bits of the previous rootstock will adulterate the new graft. Nor will the original rootstock be the same. Remains of the scion will very likely be present in all but the earliest dissections, and at any rate the stock will still have been cut down, bled, and it’s cambium scarred; making future grafts less likely to take.
 Interesting use of the word scion.