2. The maize grain.—A grain of maize is really a fruit, as a pea-pod is. A pea-pod contains several seeds; a maize fruit contains only one seed, which fills it. Notice the shape of the grain—flattened, rounded along one edge, and bluntly pointed at the opposite edge (Fig. 14). Notice a whitish patch on one of the flattened sides; a ridge (E) down the middle of this marks the position of the embryo. Cut through the grain lengthwise, so as to divide the embryo into two equal parts, and examine the cut surface (Fig. 15). Identify: (a) The embryo, lying somewhat obliquely, and to one side. The radicle (rad.) is directed towards the pointed end of the grain, and the plumule (pl.) towards the rounded end. (b) The endosperm (end): a mass of material outside the embryo, and forming at least half of the grain. (c) The scutellum (scm): a plate lying between the endosperm and the embryo. (d) The coats of the seed and fruit, surrounding the whole. Draw. Add a drop of iodine solution to the cut surface of the half-grain. The endosperm turns blue. What does this indicate? 3. The wheat grain.—A grain of wheat is also a one-seeded fruit. Notice the groove along one side, and—on the opposite side near one end—the white patch marking the position of the embryo. At the other end is a tuft of very fine hairs. Cut the grain lengthwise, so as to divide the white patch into two equal parts, and make out the embryo, endosperm, and scutellum (Fig. 16). Draw. Test the endosperm with iodine solution. Does it contain starch? [Pg 19] Grains of maize and wheat.—A grain of maize or wheat is really a one-seeded fruit. In other words, the grain consists not only of the seed with its seed-coat, but also of the seed-case. In this respect it resembles the fruit of the sycamore (p. 8). When, however, a grain of maize or wheat is carefully examined, it is found to differ greatly from all the seeds hitherto mentioned. A maize grain is somewhat flattened, and rather pointed along one edge (Fig. 14). On one flat side, near the pointed end, may be seen a whitish patch, and, along the middle line of this, a ridge which marks the position of the embryo. Fig. 14.—Maize grain, showing the position of the embryo (E). (× 4.) Fig. 15.—A longitudinal section of a Maize grain, through the middle line of the embryo. end, endosperm; pl, plumule; rad, radicle; rt, origin of a root; scm, scutellum. (× 4.) A wheat grain has a different shape. It is oval, with a deep groove running down one side. One end is clothed with a tuft of very fine hairs; near the other end, on the side opposite to the groove, is a white patch beneath which is the embryo.