Fern (Dryopteris):

Habitat:

Commonly found in moist and shady places in tropical to temperate region. Some are fond in aquatic habitat as epiphyte i.e. growing on trunk of trees.

Sporophyte:

External structure:

• The plant body is sporophytic and differentiated into root, stem,  and leaf. The root is fibrous and arises from stem. The roots are short lived and therefore called ephemeral and branched.
• The stem is underground horizontally placed, branched or unbranched. Its colour is dark brown. It is called rhizome. It is covered by brown hairs called remanta which protects young leaves from the injury and drying.
• The leaf is aerial part. It consists of thick and stout petiole. On the either side of rachis, pinnae are present. The young leaves are curved and called circinate leaves.

Internal structure:

Root:

• Transverse section of root shows that the outermost layer of root is epidermis. In young root hairs are present. Below epidermis, there is multilayered broad region of cortex, which is differentiated into two regions.
• Outer cortex is made up of thin walled parenchyma, which stores food, and transport water.
• Inner cortex is made up of thick walled sclerenchyma, which gives mechanical strength to the root.
• Below inner cortex, there is single layer of barrel shaped cells called endodermis containing chloroplasts. It stores and forms starch.
• Endodermis is followed by pericycle, which is composed of compactly arranged one, or two layers of thin walled cells. There is a vascular cylinder surrounded by pericycle. It has xylem and phloem. There are two large sized metaxylems and on either side of metaxylem small protoxylems lie at two sides. Both xylems are surrounded by phloem.

Stem:

• The outer most layers are single layered called epidermis. The epidermis is covered outwardly by a layer of non-living materials called cuticle. Below epidermis, there is multilayered broad region of cortex, which is differentiated into two regions.
• Outer cortex is made up of thick walled sclerenchymatous cell, which is called hypodermis. It gives mechanical support to the plant.
• Inner cortex is made up of thin walled parenchymatous which stores food.
• Below cortex vascular bundle is s dictyostele, which consists of a hollow and cylindrical many vascular bundles called meristeles. Each meristele has its own endodermis, pericycle, phloem, and xylem.
• The region between the meristele is called pith.
• Endodermis is the outer most layers made up of barrel shaped cells. Below it layer of thin walled parenchymatous cells present called pericycle.
• The xylem and phloem are surrounded by pericycle and either side of metaxylem protoxylem lies. The phloem surrounds the both xylems.

Spore Germination:

• Under favorable condition in soil, spores germinate by producing small tube called germ tube. The germ tube undergoes mitotic division to form uniseriate filament.
• Rhizoids are developed at the base of uniseriate filament. Uniseriate filament undergoes multiple divisions and develops into heart shaped structures called prothallus. Mature prothallus bears rhizoids at the base on ventral surface.

Gametophyte:

• The prothallus produced by germination of spore is called gametophyte, which forms male and female sex organs.
• The male sex organs - Antheridia and female sex organs - archegonia are also found developed on the ventral surface of the prothallus. The archegonia are situated below apical notch and the anheridia are situated on the posterior end of prothallus.
• The mature prothallus is green small multicellular and dorsoventrally flattened.

Sexual reproduction:

• The prothalus is monocuous. The antheridia are small, globular, and sessile.
• The antheridia remains covered by layer called jacket, which encloses about 32 spermatozoites out of which only one fuse with egg.
• Each spermatozoites are coiled multiflagellated with posterior vesicle. Vesicle helps to swim in water. The spermatozoites or male gametes come out when anteridial wall gets ruptured.
• The archegonia are small flask shaped and multicellular. The neck of archegonia consists of one binucleate neck canal cell and the Venter consists of one Venter canal cell and egg or ovum.

Fertilization:

The spermatozoites reach to the apex of archegonia by swimming in water. The spermatozoites get the way through neck when the neck canal cell and Venter canal cell dissolved and fused with egg.

The zygote is formed which is diploid. The zygote undergoes multiple divisions and develops into embryo. Form embryo root stem and leaves develop and new fern plant is produced. From the anterior superior region stem arises leaves arise from anterior inferior region and root arises from the posterior region. After development of embryo, the prothallus decays, and gametophytic generation is finished.