Lower Vascular Plant

club moss

lower vascular plant, formerly pteridophyte, also called vascular cryptogam, any of the spore-bearing vascular plants, including the ferns, club mosses, spike mosses, quillworts, horsetails, and whisk ferns. Once considered of the same evolutionary line, these plants were formerly placed in the single group Pteridophyta and were known as the ferns and fern allies. Although modern studies have shown that the plants are not in fact related, these terms are still used in discussion of the lower vascular plants. The Pteridophyte Phylogeny Group (PPG I) recognizes two unrelated classes of extant lower vascular plants: Polypodiopsida, the ferns and horsetails, and Lycopodiopsida, the lycophytes.

Vascular plants are those that possess a specialized conducting system for the transport of water, minerals, and food materials, as opposed to the more primitive bryophytes—mosses and liverworts—which lack such a system. They include both the seed plants—angiosperms and gymnosperms, the dominant plants on Earth today—and plants that reproduce by spores—the ferns and other so-called lower vascular plants.

fern

The lower vascular plants represent the oldest of land plants. In their early evolution (during the Devonian and Carboniferous periods, 419.2 million to 298.9 million years ago), there were many forms that are now extinct. The sphenophytes, for example, were once a large and diverse group of herbs, shrubs, vines, and trees but are now limited to only 15 species of horsetails; the woody lycophytes (club mosses) are entirely gone, leaving only a faint trail in their reduced modern representatives. Much of the fossil fern foliage of the Carboniferous Period is of the uncharacteristic seed ferns, which are the probable antecedents of the flowering plants. Modern ferns represent an explosion of evolution in Cretaceous times (145 million to 66 million years ago).

The lower vascular plants are not an economically important group. Though they are used locally by peoples around the world for medicines and food, their greatest value today is in horticulture (ferns). Their remains, however, provide the bulk of the world’s coal beds, and their relatively simple structure and life cycle make them extremely valuable to researchers in understanding the overall picture of plant structure and evolution.

A discussion of all types of plants is found in the article plant. For a discussion of the other types of vascular plants, see gymnosperm and angiosperm. For a discussion of the nonvascular plants, see bryophyte.