Scanning electron micrograph of a flower of chickweed, Stellaria media. The flower, 4mm in size, shows typical features of radially symmetric (actinomorphic) anatomy. The 5 russet sepals are modified leaves that protect the flower in bud. 5 white petals - modified stamens - are a visual stimulus to pollinators. 3 stamens - not visible - carry anthers that produce pollen (yellow). At the base of each is a nectary (blue). In the centre of the flower are 3 styles with feathery pale green stigmas. Insects attracted by sight receive a nectar reward for transferring pollen to the stigmas, thus effecting pollination. This general outline of anatomy is common to many flowering plants, although S. media is not strictly dependent on visiting insects, being capable of self-pollination. The number of stamens (3 here) is usually fixed in a species, but some chickweed flowers may develop as many as 8