|Flower structure (tropical) 1 - Caesalpinia pulcherrima
A flower is a reproductive structure of a plant. The Caesalpinia, illustrated below, shows the main features of a flower but different species have different arrangements of the parts.
The conspicuous part of many flowers consists of the petals which are white or brightly coloured. The petals serve to attract insects which help pollinate the flower.
The sepals are usually small and green. They enclose the flower when it is in the bud.
The male part of the flower consists of stamens. The stalk of the stamen is the filament. At the end of the filament is an anther which contains pollen grains. The pollen grains contain the male reproductive cells (gametes).
The female part of the flower consists of carpels. Each carpel consists of an ovary which contains an ovule which is the female gamete. Extending from the ovary is a style which ends in a stigma which receives the pollen from another flower.
The ovules when fertilized will become seeds, while the whole ovary will be the fruit.
The receptacle is the expanded end of the flower stalk. All the parts of the flower are attached to the receptacle.
Nectaries are swellings, often at the base of the ovary or on the receptacle, which produce a sugary solution called nectar. Insects visit the flower and drink or collect this nectar.
Half flower of Caesalpinia pulcherrima
A drawing of a half-flower is a convenient method of representing flower structure. The flower is cut in halves with a razor blade. The outline of the cut surface is drawn, and the structures visible behind these are filled in.
© D.G. Mackean