A flower consists of up to four types of modified leaves. Sepals, closed over the bud before it blooms, are outermost. One step inward lie the petals. These serve to attract pollinators, both by coloration and by scent-producing glands. Inside the petals are one or two circles of pollen-producing stamens, the flower’s “male” reproductive organs. The carpels, composed of stigma, style, ovary, and ovule, are innermost. It is the carpel that receives pollen grains and, in the case of fertilization, swells to form fruit. The carpel is believed to have evolved for protection from ovule-eating insects and other harmful elements of the environment.