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These plants are the typical vegetation of cold regions like the taiga, or boreal forest, of the northern hemisphere, or the araucaria forests of the southern hemisphere.

As the first tracheophytes, pteridophytes were also the first plants to extensively colonize the terrestrial environment forming forests. They also constituted an important source of food for terrestrial animals. By presenting conductive vessels they could be larger, a feature inherited from them by phanerogamic plants.

Their seeds are formed from differentiation of the megasporangia in the female strobiles (cones). After an oosphere is fecundated the female gametophyte originates the haploid (n) primary endosperm (nutritive tissue that covers the embryo) and the covering of the megasporangium turns into the diploid (2n) seed shell.

Like all plants pteridophytes present diplobiontic (alternation of generations, or metagenesis) life cycle.

As all plants they present a diplobiontic life cycle, i.e., alternation of generations with diploid and haploid stages. The lasting (final) stage is the diploid one.

In the male strobiles (cones) there are microsporophylls (fertile leaves of the strobile) that contain microsporangia. Within the microsporagium spore mother cells undergo meiosis and generate haploid microspores. The microspore wall develops into winglike projections (to facilitate its aerial propagation) and mitosis occurs producing two cells, the generative cell and the tube cell. The final structure containing these elements is the pollen grain.

The pollen grain relates to the alternation of generations since it is the male gametophyte (the haploid stage of the life cycle).

Pollen grains are the male gametophytes of the phanerogamic (flowering) plants. Therefore within the pollen grains the male gametes of these plants are formed by mitosis.

Ferns are constituted by small roots that come downwards from the rhizome (stem, often horizontalized). The fronds also arise from the rhizome. On the back side of each leaf of the plant there are small dustlike dots called sori (singular, “sorus”, also known as “seeds”). 

In pteridophytes gametes are made by mitosis from special cells of the gametophyte. As in all plants, in pteridophytes, meiosis is sporic, i.e., cells of the sporophyte undergo meiosis and generate spores that then by mitosis develop into the gametophyte.

Most pteridophytes have subterraneous stems parallel to the substrate called rhizomes. Xaxim is a type of pteridophyte with an aerial stem generally perpendicular to the soil and from which hundreds of roots arise to absorb water from the environment. The xaxim stem is used to make flower pots and other plant supports for gardening (also popularly known as xaxim).

In these plants meiosis takes place within structures called sorus (plural, sori), small dustlike brown dots lining the underside of fern leaves. The sori contain sporangia where reproductive cells undergo meiosis and where spores are produced.

The better known pteridophytes are the ferns and the maidenhairs, from the filicinae (filicopsida) group, and the selaginellas, mosslike plants from the lycopodineae group (lycopsida). Pteridophytes are cryptogamic plants, i.e., they are flowerless and seedless.

The microsporangia in the male strobile rupture at the right period of the year releasing thousands of pollen grains. Since their pollen grains are “winged” they can be transported by the wind over distances. When the pollen grains fall into the female strobiles they pass the micropyle and enter the pollen chamber. This process is called pollination.

Within the pollen chamber the generative cell nucleus divides forming two gametic nuclei and the tube cell elongates forming the pollen tube. The pollen tube penetrates the female gametophyte and the gametic nuclei (also known as sperm nuclei) pass through the tube; one of them unites with an oosphere (the female gamete) and forms the zygote (2n). Generally fecundation occurs one year after pollination and during this time interval the maturation of the male and of the female gametes takes place. 

The fecundation in these plants is independent from water. The gametophytes however are entirely dependent on the sporophyte (the adult plant) for nutrition and hydration. 

In the female strobiles (cones) there are megasporophylls (fertile leaves of the strobile) that contain megasporangia. In the megasporangium the spore mother cell undergoes meiosis generating four haploid cells of which three regress and one gives birth to the functional megaspore. The functional megaspore by several mitosis forms the female gametophyte that contains the oospheres (female gametes) of the plant. The female gametophyte is located within the megasporangium that has a small opening, the micropyle, through which the pollen tube enters.

The process is related to the diplobiontic life cycle (alternation of generations) since the functional megaspore generates the haploid stage of the plant (the female gametophyte). 

This group of plants can be divided into conifers (pine, sequoia, cypress), that have flowers known as strobiles (cones), cycads (very ancient gymnosperms, like the cycads used in garden architecture, that also form strobiles), gnetaceae (gnetum) and ginkgos (the known species is Ginkgo biloba).

Pteridophytes are tracheophyte (vascular) plants, i.e., they have tissues specialized in conduction of water and nutrients. Bryophytes are nonvascular plants. In pteridophytes therefore the substance transport is done through vessels and in bryophytes that transport occurs by diffusion. 

The lasting form in pteridophytes is the diploid (2n) sporophyte (the fern itself, for example). In bryophytes the lasting form is the gametophyte (n).

Prothallus is the pteridophyte gametophyte (the haploid individual that forms gametes). The gametophyte develops by mitosis from a spore.

Pteridophytes are more common in humid places because they depend on water for their gametes to fecundate one another. In humid environments their reproduction is more intense and they proliferate.

Gymnosperms are not cryptogamic as bryophytes and pteridophytes are. They are phanerogamic and so they form flowers and seeds.

The evolutionary importance of the seed is related to the plant capability of distant colonization and to the protection of the embryo. Embryocontaining seeds can be carried by water, wind and animals and germinate in different environments. This fact contributes to the exploration of a variety of ecological niches and for the diversity of plant species.

Seeds in addition protect the plant embryo against external aggressions and they also provide germination under more adequate conditions (inside the seed). These features contribute to the evolutionary success of the phanerogam.