But if there is a limb to be cut off a tree in the door yard who is likely to be delegated to the job? Every boy ought to know how to do this right. You may be acquainted with the boy who sat on the limb and sawed between the tree and himself, but you will certainly not share his fate. When you use the pruning shears on the branches and twigs of a tree or shrub you are, so to speak, cutting its fingernails or hair: but when you go up with a saw you are performing a far more serious operation. Do not forget that the life processes of the tree, the circulation of the blood, the assimilation of the food, the respiration, all go on right under the bark. The "heart" of the tree is a misnomer. That fresh moist layer which is uncovered by the skinning of a tree is the only part of the tree which is really actively alive and at work. This layer, called the cambium, extends like a tight-fitting garment over the entire tree. Every tiny twig and spur is overlaid with it. If you ever had an "infected" finger from a scratch or pin prick or cut you have some idea of the danger the tree is exposed to when the cambium layer is laid bare and the wound neglected. Compare the two drawings on this page. Look at the trees in your yard. Are there some like No. 1 and others like No. 2? In No. 1 the pruner cut a branch off close up to the main trunk. The wound was dressed with thick paint to close the pores. All around the edge of the wound was the cut edge of the cambium layer. A roll of new tissue formed there, covering a part of the wound the first year. In a year or two more the roll became broad enough to close over the smooth base where the severed limb was. The wound is healed. But look at the long stubs of No. 2. That was the work of a "tree butcher." Already the stub has begun to rot and the injury has gone far into the tree, past cure. You have seen a fine board ruined by a knot hole? That knot hole was made by careless pruning. Have you seen beautiful "curly" places in fine woodwork? Those curls or "eyes" are made by the healing over of places where limbs came off. As the cambium adds layer after layer over it, the base of the old limb becomes more and more deeply buried in the wood. Learn the principles of pruning: cut off the branch, no matter how small, close to the trunk or larger branch from which it grew; cover the wound with a dressing to prevent decay. Trees, shrubs, vines, and bushes should be pruned every year. Cut out all dead wood, and then prune to shape the tree or shrub as you want it or to produce the greatest quantity of fruit, blossoms or branches. CLEANING RUGS