The florets of each head or _capitulum_ are generally arranged into two well-defined sets--the florets of the disc, occupying the centre; and the florets of the ray, spreading more or less in a radial manner from the edge of the disc. These two sets are often of different colours, as in the Daisy, where the disc florets are of a deep yellow, while the ray florets are white or pink. In some of the Composites all the florets of each head are perfect, while in others some are perfect and some imperfect. Then, as regards the latter, they may be staminate or male florets, with no pistil; pistillate or female flowers, with no stamens; or neuter florets, possessing neither stamens nor pistil. In some few cases all the florets of one head are staminate, while the pistillate florets alone form other heads; and in these instances the two kinds of heads may be found on one plant, or only one kind may exist on the same plant. In all cases the capitulum is surrounded by one or more whorls of bracts which are often closely overlapping. The florets seldom possess a distinguishable calyx, but there is sometimes an indication of the presence of five sepals; in many, however, the calyx is represented by a whorl of hairs on the summit of the ovary. Such a whorl is known as the _pappus_, and it frequently enlarges as the fruit ripens, forming a kind of parachute that allows the fruit to be carried great distances by the wind. The hairs of the pappus are often sessile on the fruit, but sometimes mounted on the summit of a slender stalk, as in the Dandelion. Further, the hairs which constitute the pappus may be simple or feathered. [Illustration: CAPITULUM OR FLOWER-HEAD OF THE MARIGOLD, showing the _involucre_ or whorl of overlapping bracts.] The corolla frequently consists of five petals, united into a tube with as many teeth; but it is often _ligulate_ or strap-shaped, in which case the presence of five petals is often denoted by five minute teeth at the tip. Where stamens exist they are five in number, attached to the petals, and the anthers are generally united in such a manner that they form a tube within the tube of the corolla. [Illustration: FLORETS OF A COMPOSITE FLOWER. In fig. 1 the corolla is strap-shaped; in fig. 2 it is tubular.]