Division Filicophyta comprises the ferns, seedless vascular plants believed to have evolved from earlier sphenophytes or other seedless vascular plants during the Carboniferous period, about 363-290 million years ago. A very diverse group of plants, ferns are found primarily in moist tropical areas, thinning out to the north. Ferns play an important role in ecological succession, often colonizing rock crevices, old fields, or open marshes before woody vegetation. The presence of both sex organs on each gametophyte allows self-fertilization, and makes the ferns adept at long-distance dispersal.

Most ferns consist of a series of long, thin leaves growing on stems; however, some grow as stems on pond water, and some grow as epiphytes on trees in rainforests. One of the greatest mysteries of fern evolution is the nature of the initial development of the leaf.

Two popular hypotheses exist: the telome theory suggests that the leaf arose through repeated complex branchings and fusions of stem systems, while the enation theory proposes that the leaf evolved through simple stem outgrowths (enations). Though the solution to this question may be forever elusive, the characteristic shape of fern leaves with fiddleheads, acropetal growth (maturation from the base to the tip, where new tissue grows), and pinnate structure may indicate that fern leaves evolved separately from the sphenophylls (leaves of sphenophytes and conifers) and the euphylls (of angiosperms).

The life cycle of a fern follows the pattern of alternation of generations, and most ferns reproduce sexually, in this manner. A few tropical species reproduce mainly by root or leaf proliferations.

In wild ferns, the gametophyte generation, or prothallium, is rarely observed. It is usually less than 8 millimeters wide, and can support only one sporophyte before dying. Both sperm and eggs are produced in the prothallium, and the sperm fertilizes the egg in the pocket of the female sex organ (the archegonial venter) of the prothallium.

The resulting diploid zygote undergoes repeated mitosis, and develops into a sporophyte plant; this plant uptakes nutrients through the gametophyte for a short period of development, and the gametophyte then shrivels and dies. On the leaves of the mature sporophyte grow many sporangia, each of which produces spores by meiosis. These spores disperse and germinate, and then grow into gametophytes.

Procedures:
1. Diagram.
2. Write a descriptive paragraph about ferns.