Page:The Oak.djvu/93

 forms numbers of these Lammas shoots every year, and the tendency to produce them seems to be capable of being inherited.

The process of sprouting, or putting forth the shoot from the bud, is the same in all the cases. As the temperature and other conditions improve in the spring, for instance, the process of cell-division in the growing-point (and its derivatives, the young leaves, etc.) goes on rapidly, and the stores of nourishment already there and in the pith and other tissues close at hand are used up. This originates a series of currents of food materials setting slowly towards these centers of consumption from other parts of the tree, and very soon the numerous cells developed begin to absorb water with relatively enormous rapidity and vigor. This brings about two chief changes—the rapid elongation of the parts of the cone situated between the points of insertion of successive leaves (i.e., the internodes), and the almost simultaneous expansion of the hitherto small and folded leaves. Thus the rapid extension of the shoot is due almost entirely to the energetic absorption of water into cells for the most part already in existence. The chief changes which follow consist in the perfection of the structures—the development and thickening of vascular tissues, cell-walls, etc.

This process of rapid extension does not occur in the internodes between the bud-scales, or, at any rate, to a slight degree only, just sufficient to enable the shoot to throw the scales off; hence the base of the outgrown