To appreciate their importance and the mode in which the effect is produced, we must ever bear in mind the two great acts of vegetable life, that of wood-growth or growth by extension, and the wonderful morphological change of this growth into flowers and fruit. These are, in some sense, antagonistic. The first is essential to the production of timber, to the building up of the tree, and should be encouraged to do its work undisturbed, up to a certain point, that we may have a substantial frame-work by which our fruits can be supported. The latter, however, is the ultimate desideratum with fruit-growers, and in our impatience to reap a quick reward, we often resort to measures that tend to curtail the usefulness, size, and beauty, as well as the permanence of our trees. This is an illustration of the axiom, that whatever threatens the vitality of a plant, tends to make it fruitful; it calls into activity the instinctive effort to perpetuate the species by the production of seed, that may be separated from the parent, and establish a separate and independent existence, to take the place of that, the life of which is threatened. Summer pruning and pinching interferes with the growth by extension, and threatens the very life of the tree; the entire removal of all new shoots and their foliage, and the removal of the successive attempts by the tree at their reproduction, will cause its death in a little while. Their partial abstraction, as practiced in summer pruning and pinching, being an attack of the same kind, results in the formation of fruit-buds. The operations of budding and grafting upon an uncongenial stock, interrupting the circulation by ringing, by ligatures, by hacking, twisting, and bending downward, all tend to check the growth by extension, and are attended by similar results, since they are antagonistic to the mere production of wood. Shortening-in the branches of some species, which form their fruit-buds upon the shoots of the current year, has the effect to give them a fuller development, if performed during the summer, but if deferred until the following spring, it will have the directly opposite result, and will cause the production of woody shoots at the expense of the fruit.