Orchids are an old group of plants: Recent evidence shows that they have existed on Earth for about 80 million years. They are found in most environments, from deserts to rainforests and in both tropical and temperate regions. Like many flowers, they have an outer ring of sepals (in the case of orchids, three) and an inner ring of petals (also three). In most orchids, the third petal is modified into an elaborate structure called a “lip” or “labellum.” Over time these flower parts have evolved into a myriad of specialized shapes, complete with lines, spots, hairs, and warts, and that sometime produce fragrance and nectar. These odd forms have a purpose: to attract one specific pollinator. The orchid flower is fashioned precisely to fit the size, shape, and body of its pollinating insect, and in some cases even looks like the insect.
Most non-orchid flowers have separate male and female structures and granular pollen. In orchids, these parts are combined into one centralized structure called a “column”—often clearly visible protruding from the center of the flower. Here the pollen is fused into a solid mass complete with a sticky disk that affixes itself to a visiting pollinator. Some Catasetum orchids fire their pollen out of the flower onto the back of the visiting insect while the bizarre Ophrys orchids trick insects into mating with the flowers to transport pollen from one plant to another.
After pollination and fertilization, the orchid seed pod will grow and in some species produce tens of thousands of dustlike seeds—the smallest seeds of any plant in the world. These tiny seeds are carried on the wind and, unlike other seeds, do not contain any food reserves for a growing seedling. Instead, orchids have evolved a specialized relationship with particular fungi that are essential for survival and growth of the seedlings. Without this relationship, many orchid species would not be able to germinate and grow.
For years the biology of orchids remained hidden—how they survived, how they reproduced, and their specialized relationships with their pollinators. Today, scientists continue to discover new orchids and unravel their secrets.
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