Flower morphology

Basic flower morphology

In angiosperms the flower is the characteristic sexual reproductive structure, which varies enormously across the group. The bisexual flower (termed "perfect" botanically), of Ranunculus glaberrimus in the figure provides an example of the common structures. A calyx of outer sepals and a corolla of inner petals form the perianth, the non-sexual part of the flower. Next inwards grow numerous stamens that produce pollen grains, each grain producing a tiny male gametophyte from a microspore. Stamens collectively form the androecium. Finally in the middle there are carpels, which at maturity contain one or more ovules, and within each ovule is a tiny female gametophyte produced from a megaspore. Carpels also have a stigma which receives pollen and a style which connects the stigma to the ovary and enables the pollen to grow into the ovary for the female gametophyte to achieve fertilization. Carpels collectively form the gynoecium.