[Music] since the earliest of times ferns have been appreciated for their beauty and have provided shelter and sometimes [Music] food the birth of their young coiled frons is often been used in artwork such as the coru ferns are popular in our parks and Gardens and even brought indoors to enhance our living spaces there are as many as 12,000 species of ferns throughout the world some are the size of your fingernail While others are as tall as a tree in the wild ferns are successful at reproducing and spreading throughout the forest they do this by producing [Music] spores The Familiar Fern is known as a sparite if a fern frond is turned over small circular areas may be seen each of these areas is called asaurus in some ferns the sorus is unprotected in many others it is covered by a cap supported by a central stalk this protective covering is called an indusium in some ferns this covering is cup shaped the sorus itself contains numerous sacklike structures each of these is called a sporangium the outer wall of the sporangium consists of a layer of protective jacket cells as the sporangium matures a row of jacket cells enlarge to form a band known as the annulus the outer wall of each annulus cell is very thin and [Music] delicate on the opposite side of the sporangium several delicate lip cells form below the jacket there are two layers of cells called the tapetum which nourish the fertile tissue within the fertile tissue consists of spocy [Music] cells each sporicide cell is deployed containing two sets of chromosomes one from each parent as each cell matures its nucleus divides twice by the process of meiosis each daughter nucleus now contains one set of chromosomes the cyop plasm of the sparite undergoes cleavage this results in a cluster of four adhering cells called a tetrad the tetum now begins to break down depositing a very tough protective coat of Spar poinin surrounded by this thick resistant wall each cell is now called a [Music] [Music] Spore [Music] the spanda are now ready to open opening is accomplished by the annulus that encircles the sporangium the annulus begins to dry out as water evaporates from its surface the tension or pull between the remaining water molecules and the wall now increases the thick inner and side walls resist this but the thin outer walls are easily pulled inward pulling in the outer walls causes the annulus to contract much like an accordion shortening the annulus tears the lip cells apart as the annulus continues to shorten the tear enlarges and the Spore case opens further when too much water is lost the water molecules are no longer able to hold together when this happens the pull on the wall is released and the anul Springs forward closing the spangen so fast that the spores are thrown out this process is repeated in thousands of spand on a leaf so that large quantities of spores are [Music] released when spores land on a moist surface those which germinate first will form bisexual or hermaphroditic individuals a riseo emerges and attaches the sport to the soil this is followed by a sheet of cells which is the Young pite or prois a notch forms on the prois that contains dividing cells this is called the notch meristem continued growth results in a heart-shaped bisexual gametoy the lower surface is firmly attached to the soil by numerous Riso male gametangia called antheridia are formed at the posterior end of the gapy the outer wall of an antheridium consists of ring cells and a cap cell which surround fertile [Music] tissue at the anterior end of the prois close to the notch there a female gametangia called aragonia an aronium consists of a neck containing a neck Canal cell at the base of the neck there is a swollen region called the Venta that contains an egg cell gametangia of both sexes may be present at the same time or at different times the timing of their appearance will determine if there will be self- fertilization or cross fertilization in some ferns aragonia form first and when flooded with water a hormone called antheridiogen is released this hormone will stimulate adjacent plants to stop growing and form antheridia but no aragonia a bisexual gapy in a female phase May therefore be surrounded by several male gyes increasing the chances of cross [Music] fertilization being close to the soil the small gites are easily flooded when it rains this water plays an important role in fertilization water stimulates the cat cell on the antheridium to open releasing the sperm cells the flagellated sperm are now able to move within the water in search of an [Music] egg sperm consists of a spiral cell body bearing numerous flagella that move it forward water also stimulates the aragonian to open the contents of the neck Canal then diffuse into the surrounding water where they act as a sperm attractant the attractant stimulates a sperm to swim towards the open aronium then swims into the opening and moves up the neck Canal towards the egg cell fertilization is accomplished when the egg and sperm nuclei fuse this creates a single deployed cell the zygote [Music] the fertilized egg remains attached to the gide inside the aronium on the lower surface of the gide the zygote begins to divide forming the embryo's sparite plant the uppermost part of the embryo the foot absorbs nutrients from the surrounding gamify tissue as the embryo grows the Venter tissue stretches and eventually ruptures a root now grows into the soil for support and to absorb water other parts of the embryo form the first leaf and the future stem the ryome the leaf grows through the notch in the gapy to reach the sunlight eventually the ryome emerges and provides additional leaves and roots in this way a new plant is formed that matures into another spore producing Fern completing the reproductive cycle we have seen that the fern reproductive cycle contains two plants the large familiar Spore plant or sparite and a tiny gamet plant or gapy using spores to travel great distances and GTS which introduce genetic variability ferns have spread and evolved throughout the world