Page:The Oak.djvu/63

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45
THE SEEDLING AND YOUNG PLANT.
The Oak (Marshall Ward) Fig 11.jpg

To right and left in Fig. 10 are seen two strands, marked l, l, and these run chiefly in what may be called the faces of the five-angled stem; only, at the node where the leaf we are considering is inserted, they turn in towards the leaf, and eventually they run into the sides of the petiole of the leaf as the so-called "lateral strands," or bundles.

Now, observation shows that these lateral strands (marked l, l², l³, etc., in the diagram,



Fig. 11.—Diagram of the course of the vascular bundles as they come down from the leaves into the stem. The horizontal dotted lines represent the levels of sucessive leaves; the triangular white area beneath the upper letter z is the insertion of a leaf. Each group of bundles form a leaf, as mm, ms, ms, etc. (see text), descends into the stem, and joins with the bundles from other leaves after running through several internodes. The other letters refer to the bundles from other leaves. (After Frank.)