Читать книгу Field and Woodland Plants - William S. Furneaux - Страница 14

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Since flowers are the reproductive organs of the plant it seems only natural to suppose that the wonderful variety of colour and form which they exhibit might have some connexion with the processes concerned in the propagation of their respective species, and the more we study the nature of the flowers and observe the methods by which pollen is transferred from stamens to stigmas, the stronger becomes our conviction that the diversities mentioned are all more or less connected with the one great function of reproduction.

This being the case, we propose to devote a short chapter to a simple account of the uses of the parts of a flower, and to the various contrivances on the part of the plant to secure the surest and best means of perpetuating the species.

It has already been stated that the stamens produce pollen cells, and that the ovary contains one or more ovules. As soon as the anthers are mature, they open and set free the pollen cells they contained. A stigma is said to be mature when it exposes a sticky surface to which pollen cells may adhere, and on which these cells will grow. When a pollen cell has been transferred to such a stigma, it is nourished by the fluid secreted by the latter, and sends out a slender, hollow filament (the pollen tube) which immediately begins to descend through the stigma, and through the style, if any, till it reaches the ovary.