Page:The Oak.djvu/141

Rh Each of the stamens consists of a slender thread (filament) bearing on its top a four-chambered swollen anther. This contains a yellow dust, the pollen, composed of round grains (pollen grains), each with three thinner spots in its otherwise thick wall. Each of these pollen grains consists of a membrane inclosing nucleated protoplasm and food materials. When ripe the wind blows the pollen as it scatters from the dangling stamens, and some of the grains reach the stigmas of the female flowers; here they germinate, each pollen grain sending a delicate pollen-tube down the style into the ovary of the flower. This process of application of the pollen grains to the stigma is termed pollination, and depends on the wind.

The female inflorescences are also spikes (Fig. 32, A), but they bear only one to five flowers, and stand off from the axils of the foliage leaves. In the commonest English variety (Q. pedunculata) the spikes are rather long, obliquely erect, and the flowers are scattered on the upper end of the rachis of the spike; in other varieties the flowers are more clustered in the axils of the leaves. Here, as in one or two other details, minute differences are apparent in different individuals; similar trifling differences are met with in the structure of the male flowers.

Each female flower springs (like the male) from the axil of a small bract: in other respects it is very unlike the male flower. In the first place, the ovary is inferior, being sunk in and fused into a six-partite perigone, the