Botanical has a long, long discussion of the dandelion. Here's but a little bit.
"Each bloom is made up of numerous strapshaped florets of a bright golden yellow. This strap-shaped corolla is notched at the edge into five teeth, each tooth representing a petal, and lower down is narrowed into a claw-like tube, which rests on the singlechambered ovary containing a single ovule. In this tiny tube is a copious supply of nectar, which more than half fills it, and the presence of which provides the incentive for the visits of many insects, among whom the bee takes first rank. The Dandelion takes an important place among honey-producing plants, as it furnishes considerable quantities of both pollen and nectar in the early spring, when the bees' harvest from fruit trees is nearly over. It is also important from the beekeeper's point of view, because not only does it flower most in spring, no matter how cool the weather may be, but a small succession of bloom is also kept up until late autumn, so that it is a source of honey after the main flowers have ceased to bloom, thus delaying the need for feeding the colonies of bees with artificial food.
Many little flies also are to be found visiting the Dandelion to drink the lavishly-supplied nectar. By carefully watching, it has been ascertained that no less than ninety-three different kinds of insects are in the habit of frequenting it. The stigma grows up through the tube formed by the anthers, pushing the pollen before it, and insects smearing themselves with this pollen carry it to the stigmas of other flowers already expanded, thus insuring cross-fertilization. At the base of each flower-head is a ring of narrow, green bracts the involucre. Some of these stand up to support the florets, others hang down to form a barricade against such small insects as might crawl up the stem and injure the bloom without taking a share in its fertilization, as the winged insects do."
I think you can see some of those parts in these pictures: