Bordeaux mixture, the standard fungicide material, consists of a solution of 6 pounds of copper sulphate (blue vitriol) with 4 pounds of slaked lime in 50 gallons of water. It may be purchased in prepared form in the open market, and when properly made, has a brilliant sky-blue color. Spraying with Bordeaux mixture should be done in the fall, early spring, or early summer, but never during the period when the trees are in bloom. STUDY III. PRUNING TREES FUNDAMENTAL PRINCIPLES Trees are very much like human beings in their requirements, mode of life and diseases, and the general principles applicable to the care of one are equally important to the intelligent treatment of the other. The removal of limbs from trees, as well as from human beings, must be done sparingly and judiciously. Wounds, in both trees and human beings, must be disinfected and dressed to keep out all fungus or disease germs. Fungous growths of trees are similar to human cancers, both in the manner of their development and the surgical treatment which they require. Improper pruning will invite fungi and insects to the tree, hence the importance of a knowledge of fundamental principles in this branch of tree care. [Illustration: FIG. 112.--A Tree Pruned Improperly and too Severely.] Time: Too much pruning at one time should never be practiced (Fig. 112), and no branch should be removed from a tree without good reason for so doing. Dead and broken branches should be removed as soon as observed, regardless of any special pruning season, because they are dangerous, unsightly and carry insects and disease into the heart of the tree. But all other pruning, whether it be for the purpose of perfecting the form in shade trees, or for increasing the production of fruit in orchard trees, should be confined to certain seasons. Shade and ornamental trees can best be pruned in the fall, while the leaves are still on the tree and while the tree itself is in practically a dormant state. Proper cutting: All pruning should be commenced at the top of the tree and finished at the bottom. A shortened branch (excepting in poplars and willows, which should be cut in closely) should terminate in small twigs which may draw the sap to the freshly cut wound; where a branch is removed entirely, the cut should be made-close and even with the trunk, as in Fig. 113. Wherever there is a stub left after cutting off a branch, the growing tissue of the tree cannot cover it and the stub eventually decays, falls out and leaves a hole (see Fig. 114), which serves to carry disease and insects to the heart of the tree. This idea of close cutting cannot be over-emphasized.