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. 6. Starch is stored up in the twigs.—Cut off a twig and pour a drop of iodine solution on the cut end. What does the blue colour indicate? [Pg 57] 7. The growth of the bud.—Watch your bud growing, and notice that the tip of the twig—which was surrounded by the young leaves—elongates so that each pair of leaves is soon separated from the next pair. Notice the rings of scars which the scales left when they fell off. 8. A year’s growth.—Look down the twig until you find the rings or scars which were left last spring, when the scales fell off the expanding terminal bud. A year ago the end of the twig was at this point, so that the length between one such set of rings and the next marks a year’s growth. 9. Side branches.—The buds on the length formed last summer but one may have grown out into side twigs. Try to find the leaf scars below each of these side twigs. 10. A horse chestnut twig and its buds.—Examine in the same way a horse chestnut twig and trace its history. The buds are larger than those of the sycamore, and each is covered with a shining, sticky layer of resin. What do you think is the use of the resin? Put a bud in water, and when you take it out notice how the water runs off and leaves the bud dry. Pull one of the terminal buds to pieces. The scales will come apart more easily if the bud is soaked for some time in methylated spirit, to dissolve out the resin. Notice the thick layer of down inside the scales. What do you think is its use? Scrape the down gently, and carefully clean it away from the little foliage leaves in the middle. See how the leaflets of each leaf are folded. In some terminal buds you may also find a little pink flower-spray. Tie a piece of string round a growing twig, so that you can recognise it, and watch all the stages of the expansion of the terminal bud, the unfolding of the leaves, and the elongation of the tip (Figs. 37, 39 and 40). Cut off other twigs two or three feet long, in February or early March, and keep them in water in a warm room.