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Ferns, which are seedless vascular plants first developed vascular tissue, such as the xylem and phloem, which is the circulation of complex plants, much like the blood flow in animals. Most of the plants that we notice on a daily basis, including all our trees and shrubs, as well as goldenrod, grass, and floating duckweed, are vascular seed plants. These plants reproduce when male pollen* grains fertilize female ovum*. The resulting embryo* is sheltered and nourished in a specialized structure - what we call the "seed." Seed plants rely on the wind or animals to carry the pollen grains to the ovum. Many of these plants have sophisticated structures for capturing the pollen (such as flowers) and spreading the seed. Seed plants also have a well-developed system of vessels, known as a vascular system, that carries nutrients and water throughout the plant. Seed plants include all of the plants that are supported by hardened tissues-- known to most of us as wood. In other words, trees, shrubs and woody vines are all woody seed plants. Many non-woody plants (those that don't have hardened tissue) are also seed plants, including sunflowers, sedges and squash vines. |
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