The labiates.—The deadnettle is a type of an easily recognisable [Pg 118] family of plants. The stem is square in section, and the leaves are arranged upon it in opposite pairs at right angles to each other. The plants are hairy and have distinctive odours. The aroma of thyme, mint, marjoram, sage, etc., has led to the plants being used for flavouring food. None of the labiates is poisonous. The shape of the flower is very characteristic, and is specially adapted to the visits of bees. The flowers are so modified that the lowest part of the corolla forms a platform on which the bee may conveniently alight, while the upper petals unite into an arched roof which protects the pistil and stamens. Fig. 93.—Pollination of the Sage by a bumble bee. For explanation see text. (× 1.) The mechanism of cross-pollination is particularly well shown in the case of the sage (Fig. 93). The flower contains four stamens, but two of these have lost their use, and the others are modified in a strange manner. The whole stamen has somewhat the shape of a capital T, and at each end of the cross-piece is a pollen box. Usually the cross-piece (c, Fig. 93, 3) is not at right angles to the filament, but is swung up—the junction acts as a hinge—until it is nearly vertical (Fig. 93, 4). The pollen box s, which is at the lower end of the cross-piece c when this is vertical, contains hardly any pollen. [Pg 119] The entrance to the honey tube is thus guarded by two pillars, the filaments (f) of the stamens; and the lower pollen box (s) of the cross-piece of each stamen is directly in front of the bee’s head as it stands on the lower lip of the flower. When it pushes forward its head to reach the nectar it comes in contact with the lower pollen boxes, and the cross pieces swing round on their hinges, bringing the upper pollen boxes down with a smack on the bee’s back (Fig. 93, 1), and sprinkling it liberally with pollen dust. Having shed their pollen the stamens shrivel up, and the pistil comes to maturity. As the pistil ripens, the stigma arches over (Fig. 93, 2) so as to scrape along the back of any bee visiting the flower for the nectar, and thus to wipe off the pollen which has been brought from a younger flower. 25. THE LILY AND SNOWDROP FAMILIES. 1. The hyacinth.—Take up a plant (Fig. 94) entire and notice the underground bulb with roots springing from its lower surface, and the long narrow leaves. Is the venation of the leaves parallel or net-like? Is the hyacinth a monocotyledon or a dicotyledon? See the bract at the base of each flower-stalklet.