Fig. 227.—Key of Sugar Maple.
Fig. 228.—Key of Common American Elm.
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 centre 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, milkweed, also have follicles.