One characteristic of flowering plants, or angiosperms, is that they have seeds covered by a seed case. Many also reproduce through cross-pollination that is carried out by insects, birds or the wind.
Most flowers grow on receptacles, which are enlarged parts of the plant's stem. They usually have four sets of parts, called whorls, including the calyx, the corolla, stamens and pistils.
The outermost whorl is the calyx, which is made up of small, leaflike sepals. These protect the flower when it's still in bud. When the bud opens, the sepals spread out and may even wither and drop off. The corolla is usually made of brightly colored petals. These petals attract insects and birds. Petals come in many forms and can resemble tubes, slippers, bells or trumpets.
The stamens are the male reproductive organs of a flowering plant. There might be just one stamen, or there can be hundreds. They're usually separate, but they can fuse into a cup, tube or ring in some plants. The pistil is the female reproductive organ. Again, there may be one or many. The pistil is made up of the stigma, at the top; the style, a long tube; and the ovary, which is attached to the style.