Page:The Oak.djvu/94

 shoot shows a number of small scars in a close spiral. These scars of the stipular bud-scales, like those of fallen leaves, exhibit the points of rupture of the vascular bundles which ran across from the bundles of the bud-axis. It only remains to point out that the buds vary in size and vigor according to the age and condition of the tree; the buds on oaks less than fifty years old very rarely have inflorescences developed in them, and I shall defer the consideration of these till we come to the flower.

The mature leaf of the oak (Fig. 20) is obovate in general outline, with rather deep sinuses cutting the margin on each side into about six or eight rounded lobes; the apex is rounded or blunt, and some variation occurs in the degree of incision between the lobes. The base either tapers slightly into an evident petiole, or it is prolonged on either side of a very short petiole so as to form small auricles. In the commonest variety the margins and surfaces of the leaf are quite smooth, but the raceform known as Quercus sessiliflora has the young leaves pubescent beneath.

The venation consists of a midrib running from base to apex, and pinnate lateral ribs running from the mid-rib at an angle of about forty-five degrees to the tip of each lobe, the points of origin being alternate or nearly opposite, and the angle referred to subtending forward. These principal ribs are prominent below, but not at all so above. The leaf-tissue (mesophyll) between these is permeated by numerous smaller vascular bundles united