Page:The Oak.djvu/31

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13
THE ACORN AND ITS GERMINATION.

with a thin, brown, wrinkled, papery membrane, which is its own coat—the seed-coat, or testa (Fig. 2, t). The extent to which the testa remains adherent to the seed, or to the inner coat of the pericarp, and both together to the harder outer coat of the pericarp, need not be

The Oak (Marshall Ward) Fig 2.jpg
Fig. 2.—Sections of acorns in three planes at right angles to one another. A, transverse; B, longitudinal in the plane of the cotyledons, (l); C, longitudinal across the plane of the cotyledons; c, cotyledons; t, testa; p, pericarp; s, scar, and r, radicle; pl, plumule. The radicle, plumule, and cotyledons together constitute the embryo. The embryonic tissue is at r and pl. The dots in A, and the delicate veins in B and C, are the vascular bundles.

commented upon further than to say that differences in this respect are found according to the completeness and ripeness of the acorn.

Enveloped in its testa and in the pericarp, then, we find the long acorn-shaped seed, which seems at first to be a mere horn-like mass without parts. This is not the case, however, as may easily be observed by cutting the mass across, or, better still, by first soaking it in water for some hours; it will then be found that the