The largest and most advanced of all the Botanical Families is the Composite. It contains one-tenth of all known species of flowering plants, one-eighth of which are indigenous to North America. The Composites were called compound flowers by older botanists.
They are, in reality, many small flowers, called -florets, united in a compact head called a disk, upon a flat or conical receptacle, either with or without petal - like rays circled around them, all with a calyx-like involucre of green bracts underneath. The disk of the daisy contains from 200 to 500 florets. Examined under the magnifying-glass, each floret is seen to have its own tiny calyx, whose tube is joined to a 1-celled ovary in which is found a single, dry seed, an achene. The top of the calyx takes different forms, a knowledge of which is of use in classifying the flower. In the daisy it is abruptly cut off; in the chicory it is cup-shaped; in the sunflower, a pair of rabbit-like ears; in the sneeze-weed, 5 scales; in the thistle, tufts of fine hairs; in the dandelion, such tufts raised on a long handle, like a dust-brush. These developments of the calyx - top are called pappus. A single bract grows outside the calyx called chaff. The corolla is tubular, divided into 5 points at the summit. The anthers of the five stamens form a ring, on the inside of which they open, discharging their pollen on a pistil yet unripe. This with its two-cleft style and stigma, as it grows and elongates, carries the pollen with it. The insect, hovering and crawling over the florets, collects the pollen on its body, conducts it to other flowers whose pistils happen to be ripe, thus bringing about cross-pollination.
The Composites are divided into Tubuliflorae, or those with all tubular florets; and Liguliflorae, those with strap-shaped florets. In many of the first there are ray flowers arranged along the margin, which, upon examination, will be found to contain a pistil only, or to have neither pistil nor stamens. The daisy is one of the Tubuliflorae.
The strap-shaped florets have flat corollas, as if the tubes were slit open, in the disk, and no ray flowers. The dandelion is an example.