There are two divisions of seedless vascular plants. Phylum Lycophyta contains about 1,000 species usually less than two feet tall, including club mosses, spike mosses and quillworts. Most of the 11,000 species of Phylum Pterophyta live in the tropics and include ferns, whisk ferns and horsetails. They all reproduce by spores blown in the wind.
Stages of Reproduction
Seedless vascular plants have two separate reproductive phrases; each produces the other.
The gametophyte produces male or female cells that fuse together in the process of fertilization. These develop into a sporophyte, the cells of which contain two sets of chromosomes.
The sporophyte produces cells through meiosis. Meiosis is the process by which a parent cell divides into four cells, each of which contains half of the genetic material of the parent cells.
The sperm of seedless vascular plants have organelles that are whip-like, resembling tails, enabling them to swim. They require water to reproduce, limiting the plants to moist areas. An organelle is a subunit of a cell that has a specific function.
Characteristics of Phylum Lycophyta
The saporophytes of plants in the Phylum Lycophyta consist of quill-like leaves that grow spirally on a short axis. These axes are upright or horizontal. Many of these plants are epiphytes, meaning they grow on other plants without harming them. Most are hardy perennials that on the floors of forests.
Club mosses have true roots, stems and leaves.
Quillworts are aquatic; they live in ponds, lakes, swamps and rivers.
Characteristics of Phylum Pterophyta
Most plants in this phylum have microphylls, small, narrow leaves, each with a single vein.
Ferns range in size from less than an inch to a species in New Zealand that is the size of a small tree. Most ferns have above-ground leaves called fronds. When they are budding, the fronds are coiled into what are called fiddleheads. Ferns bear spores on stalks and on sporangia, clusters of cells that produce spores. The sporangia are located on the bottom of the leaves. Ferns spread horizontally on underground stems called rhizomes.
The whisk fern is the simplest vascular plant, not too different from its extinct ancestors. Whisk ferns have stems and vascular tissue but no true roots or leaves. They anchor themselves and absorb nutrients through rhizoids, branching filaments or fibers that spread through soil. Their sperm requires water to become fertile. Horsetails conduct photosynthesis through above ground stems. They contain silica in their cell walls, making them useful to Native Americans and pioneers for polishing and scrubbing.