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pith as before, and it is the cambium cylinder which has moved outwards, as it were, putting in all that solid-looking timber as it did so. The epidermis and

Fig. 26.—Photograph of the transverse section of a log of oak. about one sixth natural size. The cortex and bark are removed, and the outline is bounded by the cambium. The pith appears as a mere dot in the center; the medullary rays radiate from this, and the annual rings (about forty in number) are arranged concentrically around it. A large crack has formed along the plane of a medullary ray as the section dried. (Müller.)

the cortex of our young stem have disappeared, however, their place being taken by cork and bark. Closer inspection will show that a series of layers of phloëm