The canopy layer of tropical rain forests is said to be one of the most diverse ecosystems on the planet. It towers over the forest floor, creating a ceiling that allows very little light to reach the ground. As a result, most of the nutrients or "energy" in the forest is found in the canopy. All this energy is contained in the wealth of vegetation types found growing on tree limbs many feet in the air.
More than 2,500 vine species are known to exist within the world's tropical forests. Vines always use existing vegetation for support as they grow up toward the canopy. They sprout from the ground and attach to their host, which can be a tree or another vine. The methods of attachment seem nearly as diverse as the species themselves: some vines wrap around the host; some grow roots into the bark; others use thorns.
Bryophytes are nonvascular plants, meaning that they don't have xylem and phloem. (In contrast, the "strings" in a celery stalk are bundles of vascular tissue that carry nutrients and water through the plant.) The three types of bryophyte are the mosses, liverworts and hornworts.
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Bromeliads grow in great abundance in the rain forests. There are over 2,700 species known. These plants are able to absorb all their nutrients and water from the surrounding air. Some collect rainwater in their bases, where tree frogs will lay their eggs.
Orchids are one of the most diverse groups of plant on Earth, with over 25,000 species known. Some orchids' seeds are incredibly small, making them very well adapted to wind dispersal. Many orchid species are pollinated by only one species of animal, making their existence very unstable -- if their pollinator goes extinct, so will the flower.