“The easiest way for the sap to run from the roots to the foliage is from bottom to top in a vertical line. Anything that interferes with this course hinders also the upward impetus. Thus in branches with sharp elbows and abrupt bends the rush of sap is slackened just as the rate of flow of a water-current is diminished by the windings occurring in its bed. Thus, again, in a branch having a decided incline downward the sap moves with difficulty, because its movement toward the extremity of this branch is in a direction contrary to that which is natural to it. The application of this principle is evident. If we wish to moderate a too vigorous growth of branches, we bend them toward the ground; if we wish to stimulate a too feeble growth, we straighten up the branches until they assume a vertical posture. “We can also turn to account the exhausting effect of fruit-bearing. The more fruitful a branch is, the weaker it becomes, since the use of sap in fruit means so much the less for foliage, and it is foliage that invigorates the branch. Accordingly we will leave the greatest possible quantity of fruit on the strong part of our tree, and suppress it on the weak part.” CHAPTER XXVI MAKING FRUIT TREES BEAR “If one side of a tree is pruned very short and the other very long, the natural course of the sap is to some extent diverted from the first side toward the second, which is richer in buds and consequently in foliage. We have just seen how this principle is utilized to check the growth of too vigorous a part in order to stimulate that of one that is too feeble and thus redress the balance between the two. But what would be the result if the whole tree were pruned at once?