Roots.—The roots of maize are of two kinds : (1) Those that are formed when the kernel germinates, which develop into the strong underground feed ing roots ; (2) those that develop in a circle from the lower nodes of the stem, and serve primarily as prop or supporting roots. Before these adven titious aerial roots reach the soil, they are covered by a copious mucilaginous material, which probably prevents dry air and dry winds injuring the important growing apex. Later these air roots absorb water and plant-food from the soil into which they penetrate.
Stem.—The stem of corn, known botanically as a culm, is divided into nodes (knots) and internodes (straight stem parts). The internodes differ from those of most grasses by being solid instead of hol low. The basal part of each of the lower leaf sheaths is provided with a ring of soft tissue, which consists of cells capable of rapid growth. Hence the base of the sheath is ready at any time to grow, and if the plant is blown over by the wind, growth takes place, and the plant is thus assisted into an upright position. Another point of interest is that a number of the internodes are alternately grooved or flattened. Those persons who have made a "corn-stalk fiddle" will remember that it was this peculiar flattening, which accommodates the ears, that rendered possible the manufacture of the crude musical instrument. The sap bundles of the corn stem are isolated and of the closed collateral type.
Lea res.—The leaves of corn are two-ranked; that is, they alternate on opposite sides of the stems. Each leaf may be divided into three parts,—a sheath, which is open along one side, a ligule, or membranous outgrowth at the top of the sheath, and the blade. The ligule has been appropriately called the rainguard, as it acts in such a way that rain water with dust particles held in solution, which runs down the grooved surface of the leaf, runs otf on either side on reach ing the ligule and does not run into the space between the stem and sheathing base, where dirt might other wise easily accumulate. The folds in the margin and base of the leaf, which are formed because the edge grows more rapidly than the middle, are in genious natural or mechanical contri vances to ease the strain on the leaf blade when the wind blows. If a microscopic section is made of the leaf-blade, peculiar fan-shaped cells are found distributed in the upper epider mis between the prominent parallel veins. These are bulliform cells and in
ordinary weather absorb water and keep the leaf-blade perfectly flat. In hot, dry weather, water is lost from these cells and the leaf-blade rolls up and thus protects itself against desiccation and controls the normally high rate of transpiration, or water loss.
Flowers.— The flowers of maize are arranged in clusters in two different parts of the plant. The male (staminate) flowers together form the termi nal tassel of the plant, while the female (pistillate) flowers (Fig. 515) are placed on the cob, sur rounded by the husks in the axils of the lower, or usually the middle leaves of the stem. The stami nate flower cluster is known as a panicle of spike lets. Each ultimate division of the tassel (pani cle) is a spikelet. Each spikelet consists of two dry scales (lower glumes) subtending two flowers of three stamens each. Each staminate flower is surrounded by a flowering glume (lemma) and a pales on the inside. When the anthers are mature, they dangle at the ends of long filaments, and thus the dry, smooth pollen-grains are consigned to the wind. The pistillate flowers are placed in even numbered rows on the fleshy axis known as the cob. Each spikelet on this axis consists of two flowers, subtended by two glumes more or less horny or leathery. One pistillate flower is abortive and is represented solely by a flowering glume and a pales, while the other pistillate flower, with sub tending, flowering glume and palea, has an ovary surmounted by a long, hairy style, showing, under the microscope, two longitudinally directed vascu lar bundles. Each style, or thread of silk, is hairy, to entrap the round, smooth pollen-grains, which are produced in very great numbers, as many as 18,000,000 by a single plant. The pollen begins to be shed one to three days before the silk emerges from between the husks, and continues to fall for eight days, more or less, although the silk is pol lenized usually on the first day of its appearance, The egg apparatus in the ovule of maize consists of three cells, and in the center of the embryo-sac is an endosperm nucleus. The fertilization of the egg cell results in the formation of the corn em bryo, while the double fertilization of the endo sperm nucleus by the second sperm nucleus pro duces an immediate effect on the color of the reserve food stored about the embryo. This imme diate effect of the pollen on the offspring kernels is called xenia.