Fig. 387. Utricle (pyxis) of Amaranth, opening all round (circumscissile).
[363.] A Caryopsis, or Grain, is like an akene with the seed adhering to the thin pericarp throughout, so that fruit and seed are incorporated into one body; as in wheat, Indian corn, and other kinds of grain.
[364.] A Nut is a dry and indehiscent fruit, commonly one-celled and one-seeded, with a hard, crustaceous, or bony wall, such as the cocoa-nut, hazelnut, chestnut, and the acorn (Fig. [37], [388].) Here the involucre, in the form of a cup at the base, is called the Cupule. In the Chestnut the cupule forms the bur; in the Hazel, a leafy husk.
Fig. 388. Nut (acorn) of the Oak, with its cup or cupule.
[365.] A Samara, or Key-fruit, is either a nut or an akene, or any other indehiscent fruit, furnished with a wing, like that of Ash (Fig. [389]), and Elm (Fig. [390]). The Maple-fruit is a pair of keys (Fig. [391]).
366. Dehiscent Fruits, or Pods, are of two classes, viz., those of a simple pistil or carpel, and those of a compound pistil. Two common sorts of the first are named as follows:—
[367.] The Follicle is a fruit of a simple carpel, which dehisces down one side only, i. e. by the inner or ventral suture. The fruits of Marsh Marigold (Fig. [392]), Pæony, Larkspur, and Milkweed are of this kind.