Flowers have a long relationship with humankind, providing beauty, serving as symbols, heralding winter's end and presaging fruit to come. They are not just to look at; some flowers can also be eaten, their oils used in perfume and various parts used as medicine. Flowers, having developed before our species, have always been part of the human experience.
Flowers are the latest addition in the world of plants, having evolved last among all the other plant life. They appeared more than 100 million years ago during the Cretaceous Period, a time when dinosaurs populated the world. From their ancient beginnings, flowering plants, which are called angiosperms, have become the most widespread type of plant on land. Part of the reason is their reproductive strategy, which enlists the help of insects and animals.
A flower can have four kinds of parts: sepals, petals, stamens and pistils. Flowers with all four parts are called complete and those missing one or more of the parts are called, naturally, incomplete. Stamens and pistils are reproductive parts. If a flower has both, it's considered a perfect flower. If the plant is missing one of the reproductive parts, it's an imperfect flower. Imperfect flowers, then, must be incomplete; complete flowers must also be perfect.
Flowers are actually the sexual organs of a plant. The stamen of the flower is the male part; the pistil, the female part. The stamen produces sperm-containing pollen in its anther, which is at the top of the stamen. When pollen reaches the female pistil, pollination and fertilization can occur, which ultimately results in seed and fruit. Pollen reaches the pistil with the help of wind or insects and animals. Showy flowers, with their nectar and aroma, are tying to attract pollinators.
Flowering plants may be annuals, biennials or perennials, living one, two or three or more growing seasons, respectively. All kinds sprout from seed, then produce vegetation. Annuals then flower, produce seed in a protective covering or fruit, then die. A biennial doesn't create flowers during its first growing season. It makes food-storage parts like bulbs or tubers, then goes dormant for winter. In its second season, a biennial flower makes seeds and then dies. A perennial might flower and create seeds annually, though not necessarily at first.
Flowers have symbolized many things across cultures and throughout history. Their symbolism has led to various "flower languages," in which a flower connotes certain meanings. Floriography is a Victorian-era flower language. The Japanese flower language is hanakotoba. Symbolism also makes flowers an important part of rituals like weddings, and this intertwining of ritual and flowers is a prehistoric one. In Iraq, at the Shanidar cave, archaeologists have found evidence of flowering plants in the graves of Neanderthals buried 60,000 to 80,000 years ago.