flowers

The principal purpose of a flower is the reproduction of the individual and the species. All flowering plants are heterosporous, that is, every individual plant produces two types of spores. Microspores are produced by meiosis inside anthers and megaspores are produced inside ovules that are within an ovary. Anthers typically consist of four microsporangia and an ovule is an integumented megasporangium. Both types of spores develop into gametophytes inside sporangia. As with all heterosporous plants, the gametophytes also develop inside the spores, i. e., they are endosporic. In the majority of plant species, individual flowers have both functional carpels and stamens. Botanists describe these flowers as "perfect" or "bisexual", and the species as "hermaphroditic". In a minority of plant species, their flowers lack one or the other reproductive organ and are described as "imperfect" or "unisexual". If the individual plants of a species each have unisexual flowers of both sexes then the species is "monoecious". Alternatively, if each individual plant has only unisexual flowers of the same sex then the species is "dioecious". Flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Magnoliophyta, also called angiosperms). The biological function of a flower is to affect reproduction, usually by providing a mechanism for the union of sperm with eggs. Flowers may facilitate outcrossing (fusion of sperm and eggs from different individuals in a population) or allow selfing (fusion of sperm and egg from the same flower). Some flowers produce diaspores without fertilization (parthenocarpy). Flowers contain sporangia and are the site where gametophytes develop.