Any of the approximately 1,000 genera and 25,000 species of visually appealing plants with flowers that are found all over the world, particularly in the wet tropical regions, are called orchids (family Orchidaceae). Asparagales is an order of monocotyledonous flowering plants that also comprises the iris and asparagus families, of which the orchidaceae is a component. Because of the form of the root tubers in some species of the genus Orchis, the name orchid comes from the Greek word (orchis) for testicle. The majority of these nonwoody perennials are terrestrial or epiphytic herbs, meaning they are rooted in the soil but grow on other plants. Those that are affixed to other plants frequently resemble vines and have velamen, a spongy root coating that collects water from the surrounding atmosphere. While most species produce their own food, certain species rely on decaying organic matter (saprotrophic) or receive support for nutrition from a fungus that lives in their roots.