Page:The Oak.djvu/64

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46
THE OAK.

Fig. 11) receive contributions at successive nodes, and pass down as stronger and stronger strands through about seven internodes, their lower ends losing themselves by joining to others; and, in fact, the larger bundles seen on the transverse section (Fig. 9) are larger because they consist of so many contingents running parallel, or nearly so, down the stem.

It results from this that all the vascular bundles in the stem are simply composed of strands which run into the leaves on the one hand, and down the internodes on the other; and, as further comparison will show, all these bundles are continuous in the stem, since the lower ends of the strands are joined on to other strands.

Moreover, as an examination of the diagrams and figures shows, the main course of these bundles in the stem is approximately parallel—they run side by side down from the leaf insertion through two, three, or more internodes, and only bend aside to any great extent when they pass out into a leaf or to join with others. In the section (Fig. 9), for instance, all the little bundles at the angles and outside the ring are cut at levels where they have abandoned the larger bundles and are bending outward through the cortex to the leaves; lower down we should find them joining to the larger bundles at various levels, and running down with them, just as strands from leaves at higher levels are now conjoined to make up these larger bundles. The group of vascular bundles which passes into the