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Pericarps.—The simplest pericarp is a dry, one-seeded, indehiscent body. It is known as an akene. A head of akenes is shown in Fig. 229, and the structure is explained in Fig. 230. Akenes may be seen in buttercup, hepatica, anemone, smartweed, buckwheat.

Fig. 229.—Akenes Of Buttercup.

Fig. 230.—akenes Of Buttercup, one in longitudinal section.

A 1-loculed pericarp which dehisces along the front edge (that is, the inner edge, next the center of the flower) is a follicle. The fruit of the larkspur (Fig. 231) is a follicle. There are usually five of these fruits (sometimes three or four) in each larkspur flower, each pistil ripening into a follicle. If these pistils were united, a single compound pistil would be formed. Columbine, peony, ninebark, milk-*weed, also have follicles.

Fig. 231.—Follicle of Larkspur.

A 1-loculed pericarp that dehisces on both edges is a legume. Peas and beans are typical examples (Fig. 232); in fact, this character gives name to the pea family,—Leguminosæ. Often the valves of the legume twist forcibly and expel the seeds, throwing them some distance. The word "pod" is sometimes restricted to legumes, but it is better to use it generically for all dehiscent pericarps.

Fig. 232.—A Bean Pod.

Fig. 233.—Capsule of Castor-oil Bean after Dehiscence.

A compound pod—dehiscing pericarp of two or more carpels—is a capsule (Figs. 233, 234,