Fig. 230. Bloom of azalea.
This bud is not only ready-formed but is ready-fed. The winter shoots contain starch. On a cut surface of a dormant twig, apply a drop of tincture of iodine; note the bluish color, which is indicative of starch. This starch is insoluble; but with the first awakening of life, it changes into sugar, which is soluble and is transferred to the growing part. The burst of spring is made possible by means of this stored food. Notice the azalea in the florist's window ([Fig. 230]). The large flower-buds were formed the year before, and it is a short operation to "force" them into bloom. The flowers come in advance of the leaves; therefore these leaves could not have made the food required for the bloom. The blooming of the apple twig ([Fig. 224]) in the winter shows that the food is in the twig and buds. Once I drew a branch of a tree into a room and fastened it there. It made leaves and began to grow while the tree to which it was attached was perfectly dormant ([Fig. 231]).
Not only are the buds ready-formed and ready-fed, but they are covered. Snugly is the tender, growing part protected. Pull away the scales of a winter bud one by one. Observe how closely they are placed. Often the chinks are filled with a packing of wool, or are sealed with varnish. Dip the bud in water: then see whether the water permeates the covering. The chief value of the bud covering is not to protect from freezing, as commonly supposed, but to prevent the soft growing parts from drying out.
The plants are waiting for spring. They are ready.
Fig. 231. Branch of a tree bearing leaves inside a window, when the tree itself is dormant.