Vascular Plants Help
Introduction to Vascular Plants
Figure 9.2 (A) showed some of the most basic anatomic features of the tracheophytes (vascular plants). In addition to their inner system of hollow passageways for transporting wastes and nutrients, this group of plants has true stems and roots. The two types of vascular tissue within tracheophytes are xylem ( ZEYE -lem) and phloem ( FLOW -em). Xylem comes from the Greek for “wood,” because it often contains woody fibers that form the harder part of a plant vessel system. Xylem is stiff enough to provide support for vessel walls, and it also carries water and dissolved minerals upward into the plant after they have been absorbed by the roots. Phloem derives from the Greek for “bark.” While the outer bark of most vascular plants is tough and dead, the phloem forms a softer inner bark composed of living tissue. The phloem (living inner bark) contains vessels which carry sugars and proteins synthesized in the leaves down towards the stem and roots.
Although all tracheophytes are vascular plants, some species produce seeds, while the simpler types lack seeds.
The Ferns: Vascular Plants without Seeds
Ferns are the main group of seedless vascular plants. A fern is a slender plant with feathery fronds ( FRAHNDS ) – split “leaves” that grow out along either side of a central stem. Ferns reproduce by means of spores. The spores grow in small brownish clusters on the back of the feathery frond leaflets. Ferns, huge fern-like trees, and their close relatives grew and reproduced by the billions in ancient tropical forests. Such forests of ferns covered vast stretches of the Earth during the Carboniferous ( car -buh- NIF -er-us) Period of the Paleozoic Era, 500 to 200 million years ago. Carboniferous literally “pertains to carbon-carrying.” But it also has been nicknamed the “Age of Ferns.” The Carboniferous Period gets its name from the great forests of ferns and related plants that grew during this time, died out, and were compressed into massive layers. After millions of years, the great pressure formed deep natural deposits of coal, oil, and natural gas. Because all of these “fossil fuels” are rich in carbon atoms, naming their time of origin the Carboniferous Period or “Age of Ferns” is very fitting.
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