There are three divisions of seedless vascular plants, most of which are homosporous, where the spores grow into a gametophyte that is bisexual. These seedless types of plants have developed a vascular structure that allows nutrients and water to be transported through the system but without the production of seeds. The uptake of water became possible for these plants when they developed roots and xylem.
Also known as the fern category of seedless vascular plants, this phylum has over 11,000 species where most are tropical plants. Ferns are very diverse and have a size ranging from one inch in diameter, like the water fern, to the monstrous tree fern, which is, as indicated by the name, the size of an average tree. The major characteristics of Pteridophyta are the sporangia ,which are clusters of spores found on the underneath side of the leaves, also called fronds. In some species the spores occur on the stalk of the frond, although this is uncommon. This phylum has characteristically heart-shaped gametophytes and have multiflagellated sperm. They also require water for fertilization.
This phylum has about 1,000 species and between 10 to 15 different genera. These are small plants that grow up to 2 feet in height and include ground pines, club mosses and spike mosses. They are also common in North America as a hardy perennial that grows along the forest floor. Now extinct, there once was a giant club moss plant that grew up to 100 feet tall. A major characteristic of this phylum is they are both homosporous and heterosporous. They too require water for fertilization and have flagellated sperm.
With around 10 species, the first category within the phylum pteridophyta is the psilotales. These vascular plants have no roots or leaves and composed of simple branches which have scale growths. The spores are located on the short and lateral branches of the plant. The other category within this phylum are the equisetales, which includes the horsetails and snake grass. There is only one genus within this category and about 15 different species. Equiesetales are found in North America and can grow up to four feet in height. Some tropical species can reach up to 15 feet tall with one-inch diameter stems. Some of their major features are the hollow and ribbed stems, which are rough in texture. The stems also have well-pronounced nodes.