The Flower

A flower is the reproductive structure of a flowering plant. Though we admire it for colour and scent, its real job is to make seeds so the plant can reproduce. A typical flower is built as four rings, called whorls, attached one inside the other to the swollen tip of the flower stalk known as the thalamus or receptacle. The two outer whorls protect and attract; the two inner whorls are the actual reproductive organs.

The outermost whorl is the calyx, made of small, green, leaf-like units called sepals. The calyx covers and protects the flower while it is still a bud. Just inside it is the corolla, made of petals. Petals are usually large and brightly coloured, and they may carry scent and nectar. Their job is to attract insects, birds and other pollinators that carry pollen from flower to flower. The calyx and corolla are called the accessory or non-essential whorls because they help reproduction but do not take direct part in it.

Inside the petals lies the androecium, the male reproductive whorl, made up of stamens. Each stamen has two parts: a stalk called the filament and a swollen tip called the anther. The anther contains pollen sacs that produce tiny grains of pollen. Each pollen grain carries the male gamete. The androecium and gynoecium are the essential whorls because they take a direct part in producing seeds.

At the very centre is the gynoecium, the female whorl, made of one or more carpels (also called pistils). A carpel has three parts: the sticky stigma at the top that receives pollen, the slender style that holds it up, and the swollen ovary at the base that contains ovules. Each ovule holds the female gamete and later becomes a seed, while the ovary becomes the fruit. A flower with all four whorls is complete; one missing a whorl is incomplete. A flower with both androecium and gynoecium is bisexual; one with only one of them is unisexual.