The seeds of this class consist of a thin skin covering a mass of white or green matter, which, when ripe, constitutes the starch and flour in the Cerealia. Within that matter lies a fleshy lobe with the infant plant imbedded in one corner. The same general structure may be traced throughout the class, though the lobe with its embryo in the surrounding matter may be covered with a hard coat, as in the cocoa-nut, or inclosed in a shell covered with a rich fruit, as in the date. The infant plant, as it lies in its seed lobe, has a stem with a leaf bud or plumule at one end, and an embryo root at the other; and, as soon as the seed begins to germinate, it is nourished by the conversion of the starch of the surrounding matter into sugar. At first the whole young plant is of cellular tissue, but, as soon as the seed leaf appears above the soil, it decomposes the carbonic acid of the atmosphere, absorbs the oxygen, and consolidates the carbon. Then cords of fibro-vascular tissue are formed within it, which converge at its base, and unite with the radicle of the young plant to form the solid centre of the underground stem, from whence the real roots descend, like slender white cords, which supply the plant with food. The seed lobe having set the current of the cell sap in motion disappears, and the aërial or above-ground stem, which now consists of pith, sap, wood, and skin or bark, grows rapidly in length to its first node, or thickened part, where the first leaf or leaves appear, for the first leaves generally appear at the top of the stem in this class, and are annually succeeded by others rising above them from the top of the elongated stem, as in the palms and grasses.