The diploid sporophyte increased in dominance relegating the gametophyte to a microscopic structure within the sporophyte. The oldest fossilized vascular plant Cooksonia was discovered in both Europe and North American Silurian rock. These are the most well represented of the seedless plants. Most ferns have fronds, compound leaves divided into several leaflets. As the frond develops it uncoils from a structure called a fiddle head.
Ferns are homosporus with the leafy plant the sporophyte.
The sporangia are located on the under surface of the fronds in areas called sori . The gametophyte is a free-living, small, fragile structure. Water is necessary for fertilization since the sperm must swim to the archogonium, where fertilization takes place. As the climate began to dry out the large Fern forests began to be replaced by a new type of plant the gymnosperm. This plant had vascular tissue and a new type of reproductive structure called the seed.