The fruit of the field geranium (Fig. 133) is a long capsule composed of five carpels arranged round a central column (A). When the seeds are ripe, the carpels suddenly spring from the rod, remaining attached only at their upper ends (B), and fling the seeds into the air. The method may be watched by stroking the fruits very gently with a small brush, when they open in the manner described. The experiment is most likely to succeed in dry, sunny weather, about the middle of the day. The fruit of the poppy.—The pistil of the poppy swells during ripening into a large, globular capsule known as the poppy head. The top of the fruit (Fig. 134) is the persistent stigma. Just below this, a line of small holes like windows runs round the head. As the fruit [Pg 169] hangs inverted on the top of the flower stalk it is shaken about by the wind, and the tiny seeds fall out through the windows. Fig. 133.—Field Geranium (× ¼). Fig. 134.—A, capsule of poppy; B, cross section of capsule (× ¼); C, seeds. The fruit of the violet or pansy.—The arrangement by which the violet (Fig. 134) or pansy sows its seeds is most interesting. After fertilisation the ovary swells into a great egg-shaped capsule, in the inside of which the seeds are arranged in three rows. When the seeds have become ripe and hard, the capsule splits down the side along three lines, and is thus divided into three parts. These open outwards, and [Pg 170] bend back as shown in Fig. 135. Each is a boat-shaped valve. The seeds inside are thus exposed to the air, and they soon dry and become ready for scattering. Fig. 135.—Violet. F, explosive fruit; S, seeds being shot out of fruit. Then the curved sides of each valve begin to straighten and come together, and naturally allow less and less room for the hard, smooth seeds inside. The pressure of the sides of each valve on the seeds inside it becomes greater and greater, until one by one they are shot out to a considerable distance. If a ripe violet ovary be warmed before the fire the whole operation may easily be watched. The process may be imitated by putting a pea between two flat rulers and pressing the rulers together, when the pea may be shot to a distance of several yards.