Page:The Oak.djvu/148

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THE OAK.

morphological meaning in the light of modern biology, but the limits and purpose of this little book will not admit of that, and I must content myself with this brief résumé.

During this process of fertilization the cupule has grown up like a scaly wall round the ovary (Fig. 34), and the tip of the latter is seen peeping out from its orifice.

We are now in a position to understand generally the changes that convert the female flower into the cupped acorn. The fertilized oöspore becomes the embryo (Fig. 35, x); it grows at the expense of the contents of the embryo-sac, and develops a radicle, a plumule, and two relatively large cotyledons, which soon become so big that they occupy the whole space in the sac (Fig. 36). Moreover, the embryo-sac increases to make more room for this growing embryo. And now comes in a curious point. We saw that the ovary consisted of three chambers, each containing two ovules; each of these six ovules also had its embryo-sac, containing an egg-cell, etc., and each of the total of six egg-cells may be fertilized by the contents of so many pollen-tubes coming from pollen grains on the stigmas. But the rule is that five of the ovules with their contents perish at an early period, because one strong one takes the lead in development, and starves the rest by taking all the available nourishment to itself. Consequently the advancing ovary is soon filled by one ovule — the other five and two of the chambers being pressed to one side by it.