Now if the bark is injured, or any part of the stem, all parts below the wound are cut off from the return supply of digested food and their growth is checked. When such a wound does occur, or if a wound is made by cutting off a branch, the cambium sets to work to repair the damage by pushing out a new growth which tends to cover the wound. We can help this by covering the wound and keeping the air from it to prevent its drying and to keep disease from attacking it before it is healed. HOW THE WORK OF THE STEM MAY BE INTERFERED WITH If there are any peach trees near by, examine the trunks close to the ground, even pulling away the soil for a few inches. You will very likely find a mass of gummy substance oozing from the tree. Pull this away and in it and in the wood under it will be found one or more yellowish white worms. These are tree borers. They will be found in almost all peach trees. They interfere with the work of the stem and in many cases kill the trees. These worms may be kept somewhat in check by keeping papers wrapped about the lower part of the tree. But the surest way to keep them in check is to dig them out, spring and fall, with a knife and wire. Borers attack the other fruit trees and also ornamental trees and shrubs. Rabbits sometimes gnaw the bark from trees during severe winters. Careless workmen sometimes injure the bark of trees by allowing plows and mowing machines or other tools which they are using among them to come in contact with the trees and injure the bark. Young trees purchased from the nursery generally have a label fastened to them with a piece of wire. Unless this wire is removed or is carefully watched and enlarged from time to time it will cut into the bark as the stem grows and interfere with its work and often kill the top of the tree or injure a main branch. These are a few ways in which the work of the stem is sometimes checked and the plant injured thereby. CHAPTER XV FLOWERS In our study of the parts of plants the flower and fruit have been given the last place because in the growing of most farm plants a knowledge of the functions of the flower is of less importance than that of the roots, leaves and stems. However, a knowledge of these parts is necessary for successful fruit culture and some other horticultural industries. As with the other parts of the plant our study will not be exhaustive but will be simply an attempt to bring out one or two important truths of value to most farmers. In the study of flowers the specimens used for study will depend upon the time of the year in which the studies are made and need not necessarily be the ones used here for illustration. FUNCTION OR USE OF FLOWERS TO PLANTS Of what use is the flower to the plant? You have doubtless noticed that most flowers are followed by fruit or seed vessels. In fact, the fruit and seeds are really produced from the flower, and the work of most flowers is to produce seeds in order to provide for new plants.