CHAPTER XV

WINTER AND DORMANT BUDS

=A bud is a growing point=, terminating an axis either long or short, or being the starting point of an axis. _All branches spring from buds._ In the growing season the bud is active; later in the season it ceases to increase the axis in length, and as winter approaches the growing point becomes more or less thickened and covered by protecting scales, in preparation for the long resting season. This resting, dormant, or winter body is what is commonly spoken of as a “bud.” A winter bud may be defined as an _inactive covered growing point_, waiting for spring.

_Structurally, a dormant bud is a_ =shortened axis= _or_ =branch=, _bearing miniature leaves or flowers or both, and protected by a covering._ Cut in two, lengthwise, a bud of the horse-chestnut or other plant that has large buds. With a pin separate the tiny leaves. Count them. Examine the big bud of the rhubarb as it lies under the ground in late winter or early spring; or the crown buds of asparagus, hepatica, or other early spring plants. Dissect large buds of the apple and pear (Figs. 137, 138).

[Illustration: FIG. 137.--BUD OF APRICOT, showing the miniature leaves.]

[Illustration: FIG. 138.--BUD OF PEAR, showing both leaves and flowers. The latter are the little knobs in the center.]

_The bud is protected by firm and dry scales._ These scales are modified leaves. The scales fit close. Often the bud is protected by varnish (see horse-chestnut and the balsam poplars). Most winter buds are more or less woolly. Examine them under a lens. As we might expect, bud coverings are most prominent in cold and dry climates. Sprinkle water on velvet or flannel, and note the result and give a reason.

=All winter buds give rise to branches=, _not to leaves alone_; that is, the leaves are borne on the lengthening axis. Sometimes the axis, or branch, remains very short,--so short that it may not be noticed. Sometimes it grows several feet long.

_Whether the branch grows large or not depends on the chance it has_,--position on the plant, soil, rainfall, and many other factors. The new shoot is the unfolding and enlarging of the tiny axis and leaves that we saw in the bud. If the conditions are congenial, the shoot may form more leaves than were tucked away in the bud. The length of the shoot usually depends more on the lengths of the internodes than on the number of leaves.

[Illustration: FIG. 139.--LEAF-SCARS.--Ailanthus.]

=Where Buds are.=--_Buds are borne in the_ =axils= _of the leaves_,--in the acute angle that the leaf makes with the stem. When the leaf is growing in the summer, a bud is forming above it. When the leaf falls, the bud remains, and a scar marks the place of the leaf. Fig. 139 shows the large leaf-scars of ailanthus. Observe those on the horse-chestnut, maple, apple, pear, basswood, or any other tree or bush.

Sometimes two or more buds are borne in one axil; the extra ones are =accessory= or =supernumerary= buds. Observe them in the Tartarian honeysuckle (common in yards), walnut, butternut, red maple, honey locust, and sometimes in the apricot and peach.

If the bud is at the end of a shoot, however short the shoot, it is called a =terminal bud=. _It continues the growth of the axis in a direct line._ Very often three or more buds are clustered at the tip (Fig. 140); and in this case there may be more buds than leaf scars. Only one of them, however, is strictly terminal.

[Illustration: FIG. 140.--TERMINAL BUD BETWEEN TWO OTHER BUDS.--Currant.]

A bud in the axil of a leaf is an =axillary= or =lateral= bud. Note that there is normally at least one bud in the axil of every leaf on a tree or shrub in late summer and fall. The axillary buds, if they grow, are the _starting points of new shoots the following season_. If a leaf is pulled off early in summer, what will become of the young bud in its axil? Try this.

[Illustration: FIG. 141.--A GIGANTIC BUD.--Cabbage.]

_Bulbs and cabbage heads may be likened to buds_; that is, they are condensed stems, with scales or modified leaves densely overlapping and forming a rounded body (Fig. 141). They differ from true buds, however, in the fact that they are condensations of whole main stems rather than embryo stems borne in the axils of leaves. But bulblets (as of tiger lily) may be scarcely distinguishable from buds on the one hand and from bulbs on the other. Cut a cabbage head in two, lengthwise, and see what it is like.

The buds that appear on roots are unusual or abnormal,--they occur only occasionally and in no definite order. Buds appearing in unusual places on any part of the plant are called =adventitious buds=. Such usually are the buds that arise when a large limb is cut off, and from which suckers or water sprouts arise.

[Illustration: FIG. 142.--FRUIT-BUD OF PEAR.]

[Illustration: FIG. 143.--THE OPENING OF THE PEAR FRUIT-BUD.]

[Illustration: FIG. 144.--OPENING PEAR LEAF-BUD.]

[Illustration: FIG. 145.--OPENING OF THE PEAR-BUD.]

=How Buds Open.=--_When the bud swells, the scales are pushed apart, the little axis elongates and pushes out._ In most plants the outside scales fall very soon, _leaving a little ring of scars_. With terminal buds, this ring marks the end of the year’s growth: how? Notice peach, apple, plum, willow, and other plants. In some others, all the scales grow for a time, as in the pear (Figs. 142, 143, 144). In other plants the inner bud scales become green and almost leaf-like. See the maple and hickory.

=Sometimes Flowers come out of the Buds.=--Leaves may or may not accompany the flowers. We saw the embryo flowers in Fig. 138. The bud is shown again in Fig. 142. In Fig. 143 it is opening. In Fig. 145 it is more advanced, and the woolly unformed flowers are appearing. In Fig. 146 the growth is more advanced.

[Illustration: FIG. 146.--A SINGLE FLOWER IN THE PEAR CLUSTER, as seen at 7 A.M. on the day of its opening. At 10 o’clock it will be fully expanded.]

[Illustration: FIG. 147.--THE OPENING OF THE FLOWER-BUD OF APRICOT.]

[Illustration: FIG. 148.--APRICOT FLOWER-BUD, enlarged.]

Buds that contain or produce only leaves are =leaf-buds=. Those which contain only flowers are =flower-buds= or =fruit-buds=. The latter occur on peach, almond, apricot, and many very early spring-flowering plants. The single flower is emerging from the apricot bud in Fig. 147. A longitudinal section of this bud, enlarged, is shown in Fig. 148. Those that contain both leaves and flowers are =mixed buds=, as in pear, apple, and most late spring-flowering plants.

[Illustration: FIG. 149.--FRUIT-BUDS AND LEAF-BUDS OF PEAR.]

_Fruit buds are usually thicker or stouter than leaf-buds. They are borne in different positions on different plants._ In some plants (apple, pear) they are on the ends of short branches or spurs; in others (peach, red maple) they are along the sides of the last year’s growths. In Fig. 149 are shown three fruit-buds and one leaf-bud on _E_, and leaf-buds on _A_. See also Figs. 150, 151, 152, 153, and explain.

[Illustration: FIG. 150.--FRUIT-BUDS OF APPLE ON SPURS: a dormant bud at the top.]

[Illustration: FIG. 151.--CLUSTER OF FRUIT-BUDS OF SWEET CHERRY, with one pointed leaf-bud in center.]

[Illustration: FIG. 152.--TWO FRUIT-BUDS OF PEACH with a leaf-bud between.]

[Illustration: FIG. 153.--OPENING OF LEAF-BUDS AND FLOWER-BUDS OF APPLE.]

“_The burst of spring_” means in large part the opening of the buds. _Everything was made ready the fall before. The embryo shoots and flowers were tucked away, and the food was stored._ The warm rain falls, and the shutters open and the sleepers wake: the frogs peep and the birds come.

=Arrangement of Buds.=--We have found that leaves are usually arranged in a definite order; buds are borne in the axils of leaves: therefore _buds must exhibit phyllotaxy_. Moreover, branches grow from buds: branches, therefore, should show a definite arrangement; usually, however, they do not show this arrangement because _not all the buds grow and not all the branches live_. (See Chaps. II and III.) It is apparent, however, that the mode of arrangement of buds determines to some extent the form of the tree: compare bud arrangement in pine or fir with that in maple or apple.

[Illustration: 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 vigor 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 ones are not near the tip, there is some special reason for it. Can you state it? Examine the shoots on trees and bushes.

[Illustration: FIG. 155.--AN APPLE TWIG.]

[Illustration: FIG. 156.--Same twig before leaves fell.]

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 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 vigor 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. =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 growths. 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 buds 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 color 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 Norway maple: What do you learn?

[Illustration: FIG. 157.--BUDS OF THE HICKORY.]