Fig. 154.—Oak Spray. How are the leaves borne with reference to the annual growths?
The uppermost buds on any twig, if they are well matured, are usually the larger and stronger and they are the most likely to grow the next spring; therefore, branches tend to be arranged in tiers (particularly well marked in spruces and firs). See Fig. [154] and explain it.
Winter Buds show what has been the Effect of Sunlight.—Buds are borne in the axils of the leaves, and the size or the vigour of the leaf determines to a large extent the size of the bud. Notice that, in most instances, the largest buds are nearest the tip (Fig. [157]). If the largest buds are not near the tip, there is some special reason for it. Can you state it? Examine the shoots on trees and bushes.
Suggestions.—Some of the best of all observation lessons are those made on dormant twigs. There are many things to be learned, the eyes are trained, and the specimens are everywhere accessible. 123. At whatever time of year the pupil takes up the study of branches, he should look for three things: the ages of the various parts, the relative positions of the buds and the leaves, the different sizes of similar or comparable buds. If it is late in spring or early in summer, he should watch the development of the buds in the axils, and he should determine whether the strength or size of the bud is in any way related to the size and the vigour of the subtending (or supporting) leaf. The sizes of buds should also be noted on leafless twigs, and the sizes of the former leaves may be inferred from the size of the leaf-scar below the bud. The pupil should keep in mind the fact of the struggle for food and light, and its effects on the developing buds.
| Fig. 155.—An Apple Twig. | Fig. 156.—Same twig before leaves fell. |
124. The bud and the branch. A twig cut from an apple tree in early spring is shown in Fig. [155]. The most hasty observation shows that it has various parts, or members. It seems to be divided at the point f into two parts. It is evident that the part from f to h grew last year, and that the part below f grew two years ago. The buds on the two parts are very unlike, and these differences challenge investigation.—In order to understand this seemingly lifeless twig, it will be necessary to see it as it looked late last summer (and this condition is shown in Fig. [156]). The part from f to h,—which has just completed its growth,—is seen to have its leaves growing singly. In every axil (or angle which the leaf makes when it joins the shoot) is a bud. The leaf starts first, and as the season advances the bud forms in its axil. When the leaves have fallen, at the approach of winter, the buds remain, as seen in Fig. [155]. Every bud on the last year’s growth of a winter twig, therefore, marks the position occupied by a leaf when the shoot was growing.—The part below f, in Fig. [156], shows a wholly different arrangement. The leaves are two or more together (aaaa), and there are buds without leaves (bbbb). A year ago this part looked like the present shoot from f to h,—that is, the leaves were single, with a bud in the axil of each. It is now seen that some of these bud-like parts are longer than others, and that the longest ones are those which have leaves. It must be because of the leaves that they have increased in length. The body c has lost its leaves through some accident, and its growth has ceased. In other words, the parts at aaaa are like the shoot fh, except that they are shorter, and they are of the same age. One grew from the end or terminal bud of the main branch, and the others from the side or lateral buds. Parts or bodies that bear leaves are, therefore, branches.—The buds at bbbb have no leaves, and they remain the same size that they were a year ago. They are dormant. The only way for a mature bud to grow is by making leaves for itself, for a leaf will never stand below it again. The twig, therefore, has buds of two ages,—those at bbbb are two seasons old, and those on the tips, of all the branches (aaaa, h), and in the axil of every leaf, are one season old. It is only the terminal buds that are not axillary. When the bud begins to grow and to put forth leaves, it gives rise to a branch, which, in its turn, bears buds.—It will now be interesting to determine why certain buds gave rise to branches and why others remained dormant. The strongest shoot or branch of the year is the terminal one (fh). The next in strength is the uppermost lateral one, and the weakest shoot is at the base of the twig. The dormant buds are on the under side (for the twig grew in a horizontal position). All this suggests that those buds grew which had the best chance,—the most sunlight and room. There were too many buds for the space, and in the struggle for existence those that had the best opportunities made the largest growth. This struggle for existence began a year ago, however, when the buds on the shoot below f were forming in the axils of the leaves, for the buds near the tip of the shoot grew larger and stronger than those near its base. The growth of one year, therefore, is very largely determined by the conditions under which the buds were formed the previous year. Other bud characters. 125. It is easy to see the swelling of the bud in a room in winter. Secure branches of trees and shrubs, two to three feet long, and stand them in vases or jars, as you would flowers. Renew the water frequently and cut off the lower ends of the shoots occasionally. In a week or two the buds will begin to swell. Of red maple, peach, apricot, and other very early-flowering things, flowers may be obtained in ten to twenty days. 126. The shape, size, and colour of the winter buds are different in every kind of plant. By the buds alone botanists are often able to distinguish the kinds of plants. Even such similar plants as the different kinds of willows have good bud characters. 127. Distinguish and draw fruit-buds of apple, pear, peach, plum, and other trees. If different kinds of maples grow in the vicinity, secure twigs of the red or swamp maple, and the soft or silver maple, and compare the buds with those of the sugar maple and the Norway maple. What do you learn?
Fig. 157.—Buds of the Hickory.