A fern is a sort of plant with about 12,000 species known. Like mosses they also bear xylem and phloem. They also bear roots, stems and leaves like other vascular plants but they lack seeds and blossoms. They produce spores. The usual examples are horsetails, whisk ferns, marattioid ferns, and ophioglossoid ferns.
The term pteridophyte also refers to ferns. A pteridologist research about ferns and lycophytes. Fossil record suggests that they evolved 360 million years ago in the Carboniferous period but majority of those living ferns are about 145 million years old which evolved in the Cretaceous. They’re not so significant from the commercial point of view but are grown for ornamentation, food or remediating soils. Some are weeds and some hold special place in mythology, culture and art.
Ferns are vascular plants differing from lycophytes by having true leaves. They differ from gymnosperms and angiosperms in lacking seeds and blossoms but bear spores. Their life cycle shows alternation of generation which means it consists of diploid sporophytic and a haploid gametophytic stage. A sporophytic phase produces haploid spores by meiosis. A spore grows by mitosis and creates gametophyte which develops photosynthetic prothallus. A mobile, flagellated sperm fertilizes the egg which is connected to the prothallus. A zygote that’s currently diploid produces sporophyte by mitosis.
They prefer to live in a wide array of habitats ranging from remote mountain elevations, to dry desert stone faces, to bodies of water or in open areas. Generally they prefer four types of habitats namely moist, shady forests; crevices in rock faces, particularly when sheltered from the full sun; acid wetlands including bogs and swamps; and tropical trees, where many species are epiphytes.
Many are known to produce relationships with mycorrhizal fungi. The spores are rich source of lipids, protein and carbs so are consumed by some animals. The stem is usually a underground rhizome but in some cases it is a ground creeping stolon or semi-woody tree trunk. The leaves are green and photosynthetic and are known as fronds due to their horizontal arrangement. Tropophylls participate only in photosynthesis such as the leaves of other vascular plants. Sporophylls produce spores and compared with the scales of pines. In addition they photosynthesize like tropophylls. Brophophylls produce abnormally high number of spores. The roots are underground and non-photosynthetic. They are fibrous like other vascular plants.
Prothallus is green, photosynthetic structure generally one cell thick. It’s heart of kidney shaped measuring 3-10 mm long and 2-8 mm wide. It produces gametes in the form of antheridia and archegonia. Anteridia are small spherical structures which produce flagellated sperms. Archegonia are flask-shaped structures which produce single egg. Rhizoids are root like construction that absorbs water and minerals. They anchor prothallus to dirt.