10. THE STRUCTURE AND USES OF BUDS.
1. A typical bud.—Split a cabbage, or a lettuce “heart,” down the middle, and observe how the leaves are arranged round the conical end of the stalk. The leaves which are fixed lowest on the stalk are the largest, and they cover the outside of the bud. The leaves are smaller and smaller as they are fixed nearer and nearer the end of the stalk, until round the tip they are almost too small to be recognised as leaves. A bud is the tip or “growing point” of a stem or branch, together with the young leaves which crowd round it. Draw the section.
2. A sycamore twig.—Look in the axils ([p. 47]) of the leaves of a sycamore twig in summer or autumn, and notice the buds. Can you see any buds on the lower parts of the twig—which bore leaves twelve months or longer ago? Did these also arise in the axils of leaves? How can you be sure they did? Tie a piece of string, or tape, round this twig and look at it often, making a note of every change which you see in it.
3. The fall of the leaf.—On what date did you first notice that the leaves of the sycamore were falling? Did the first leaves fall from the twigs at, or near, the ends of the branches, or lower down near the trunk? Examine the scar left by the first leaf which falls from your twig. What is its shape? What is the meaning of the dark dots on the scar? Gently take off the leaf nearest to the scar. Does it come off easily? Are there any dark dots on this scar? Can you see anything on the end of the leaf stalk corresponding to the dots? Do you think the dots are the ends of the food pipes referred to on [p. 53]?
Make a drawing of a fallen leaf and write down on the drawing at the proper place, the colour of that part of the leaf, or better still, colour the drawing with water-colour paints. Collect good specimens of the autumn leaves of as many other trees as possible, and make coloured drawings of them.
On what date did you first notice that all the leaves were shed? Make similar notes for other trees.
4. The structure of a sycamore bud.—In winter take off a sycamore twig which has a big bud at the end, and examine it. The bud is clothed with overlapping scales of a pale green colour. Make a drawing of the bud, double the size, and then take off the scales one by one and count them. Look with a lens at the upper end of one of the largest scales. Can you see any trace of a rudimentary leaf blade? When the last scale is removed there remains on the end of the twig a tiny tuft of delicate green leaves surrounded by a little down. Count them, and notice how each is folded up fanwise. In some buds you may find a bunch of green flowers in the middle. These buds are larger than those containing leaves only.
Cut a bud across with a sharp knife, and examine the cut surface with a lens to see more clearly how the scales and young foliage leaves are arranged. Draw what you see.
5. How the bud bursts.—In spring watch your twig very carefully to be sure you do not miss any stage of the opening of the buds. Make drawings every day or two of the end bud, when it has begun to unfold. Notice how the scales fall off—those on the outside first—and how the foliage leaves push open the upper scales and come out. Watch the way in which each leaf opens its folds and spreads itself out flat.
The buds may be made to open earlier by cutting off a twig about two or three feet long and keeping it in water in a warm room.