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.
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.
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.
[Illustration: FIG. 68. A horse-chestnut stem showing leaves, buds, and scars where last year's leaves dropped off.]
[Illustration: FIG. 69.--AN UNDERGROUND STEM Buds show distinctly at points indicated by _b_.]
To understand how this comes about it will be necessary to study the parts of the flower and find out their individual uses or functions.
If we take for our study any of the following flowers: cherry, apple, buttercup, wild mustard, and start from the outside, we will find an outer and under part which in most flowers is green. This is called the calyx (Figs. 70-74). In the buttercup and mustard the calyx is divided into separate parts called sepals. In the cherry, peach and apple, the calyx is a cup or tube with the upper edge divided into lobes.