Order of true ferns - Filicales

Includes the vast majority of modern ferns, over 9000 species. They are most diversely represented in the tropics, where there are also arboreal forms.

In temperate zones, true ferns are perennial herbaceous plants with underground rhizomes. In most species, the rhizome has shortened internodes; large leaves develop annually at its top in the spring; at their base there are rudiments of leaves of the next generations. Every autumn the leaves die and underground parts of the petioles remain on the rhizome. As a result, the rhizome is completely covered with the bases of the petioles of dead leaves, which makes them thicker.

Some types of ferns have rhizomes with elongated internodes, on which leaves develop singly, at some distance from each other. This rhizome is free of old petioles.

On the rhizome, as well as on the petioles and leaves, there are often special brown or yellowish scales. These are expanded dry hairs characteristic of ferns.

The fern plant represents its asexual generation - the sporophyte. Despite the great diversity of this group of plants, a general plan is noted in the development cycle. On the underside of the leaves, along the veins or along their edges, small sporangia develop in large numbers, arranged in groups - sori. Sori in different types ferns various shapes and are often covered with a thin colorless blanket - indusium.

Sporangia mostly have the shape of rounded boxes sitting on long stalks. In the sporangia of a male fern, for example, 48 are formed, and up to 50 million spores develop on just one plant. The wall of the sporangium is single-layered; one row of cells is formed in it with an uneven thickening of the membrane, the so-called ring, which facilitates the opening of the sporangium and the scattering of spores.

The spores have a thick tuberculate shell, dark in color. Finding themselves in favorable conditions, they germinate to form the sexual generation of ferns - the gametophyte.

The prothallus looks like a small green plate, usually heart-shaped, about 1 cm in diameter. The plate is mostly single-layered, with only several layers of cells near the notch. On the lower surface of the shoot, in its elongated part, there is a large number of colorless unicellular rhizoids that attach it to the soil. The organs of sexual reproduction are also located here. Archegonia are immersed in multicellular tissue near the recess of the prothallus; antheridia protrude above the surface among the rhizoids. Spermatozoa, attracted by mucus secreted from the archegonium, penetrate the egg. This is facilitated by the contact of the shoot with moist soil.

From the zygote formed as a result of fertilization, a sporophyte embryo develops, which develops rapidly, feeding initially at the expense of the gametophyte. Suction nutrients carried out using a special leg of the embryo, which penetrates its tissue. After the formation of the root, stem and first leaf, the embryo begins to feed independently. The primary root is soon replaced by adventitious roots that arise at the base of the stem. From the bud it gradually forms mature plant. The growth is destroyed. This completes the development cycle of the fern.

The order of true ferns is divided into families and genera mainly on the basis of the structure of the ring on the sporangium (complete, incomplete, transverse, longitudinal, apical, oblique, etc.), the structure of the industrial spathe (shape, nature of attachment), the location of the sori on the leaf - vayee (along the vein, along the edge of the leaf, etc.).

The most widespread and numerous family of centipedes is Polypodiaceae, which includes all types of ferns found in Karelia.

Representatives of the family, distributed throughout to the globe, are herbs with leaves curled into a spiral in bud formation. In most species of millipedes, the leaves are double-pinnate, that is, divided into segments of the first and second orders. Less commonly, they are once- or thrice-pinnate, with segments of three orders.

In most species, spore-bearing leaves do not differ in size, shape and color from vegetative leaves. In rare cases, such differences occur when sporangia are located on special spore-bearing leaves. Sporangia are collected in round, oval or linear sori with or without veils. Sori are located on the lower surface of the frond, along the veins or along its edge. Sporangia are on long stalks, have a vertically incomplete ring surrounding the sporangium for 2/3 of its circumference.

There are about 100 species of millipedes in the Soviet Union. On the territory of Karelia, 28 species of these ferns belonging to 14 genera are found in various habitats. Among them the most common forest species, usually forming more or less closed groups in grassy green-moss coniferous forests, as well as small-leaved forests (needle-leaved shield, male shield, female nomad, Linnaeus holocum, beech telepteris). In the pine forests sandy soils common bracken forms thickets.

The vast majority of species are plants of shady habitats. Some representatives have adapted to life in arid conditions (woodzia elbe, common centipede, brittle bladder). Ferns of this group are common in open, brightly lit places with insufficient water supply and sharp temperature fluctuations. Such plants are distinguished by the characteristics of xerophytes: small sizes, leathery leaves with a waxy coating or pubescence on the lower surface. If there is a lack of moisture, they curl, leaving the hairless side inside, which protects the plant from excessive loss of moisture. After rain, the leaf straightens again.

Elbian Woodsia - Woodsia ilvensis (L.) R. Br.

A low-growing, densely pubescent fern, reaching a height of 10-20 cm. It has a thick, short rhizome.

The leaves are dull green, covered on both sides with brown scales and long hairs with a thick, shiny petiole. The leaf blade is equal to the petiole or longer, oblong-lanceolate in outline, doubly pinnately dissected.

The sori are located along the edge of the terminal lobes close to each other and merge. The veil is saucer-shaped, wavy, dissected into hair-like lobes, attached under the sorus. Sori ripen in the second half of summer - early autumn.

It is rare in Karelia, more often in the southern regions in rock cracks.

Brittle bladder - Cystopteris filix-fragilis (L.) Bordas.

A low-growing fern, 10-30 cm high, with a short, thick brown rhizome, on which leaves are located in a bunch.

The leaves are bare, thin, oblong-lanceolate in outline, pointed at the apex, narrowed towards the base, doubly pinnately dissected. The petioles are fragile, usually shorter than the blades.

The sori are round and arranged in rows along the vein. The spathe is oval, attached by the edge at one point, and falls off when the sorus matures. The spores are spiny and ripen in mid-summer.

Quite often found on rocky outcrops almost throughout the entire territory of Karelia, in the north - rarely.

The plant is poisonous, especially spores containing hydrocyanic acid. Young leaves have an almond scent.

Common ostrich - Matteuccia struthiopteris (L.) Tod.

A characteristic feature of the ostrich bird is a clear separation of vegetative and spore-bearing leaves. In the spring, large green leaves develop on the rhizome in a funnel-shaped rosette, and in the summer, 2-3 smaller brown spore-bearing leaves appear in the center of the funnel.

The vegetative leaves are doubly pinnately dissected, with a short petiole, pointed at the apex, gradually tapering towards the base.

Sporiferous leaves overwinter, once pinnate, with segments directed upward. The edges of the segments are strongly curved on the lower side, almost to the midrib. Under their cover there are sori of sporangia, sitting in groups on the lateral veins. The spores ripen in August, and by this time the initially green spore-bearing leaf turns brown.

Ostrich has a thick creeping rhizome of black-brown color. Plant height is 60-100 cm.

It is found throughout Karelia in places - in damp shady forests, more often in spruce forests along the banks of streams, usually forming almost pure thickets.

Rhizome decoction folk medicine used as an anthelmintic. It is used as an insecticide. As an ornamental plant, it can be bred for planting in shaded and humid areas of gardens and parks.

Male shieldweed - Dryopteris filix mas (L.) Schott.

The relatively thick rhizome of the male fern is located at a shallow depth in the soil. Its top rises somewhat above its surface and annually produces a bunch containing 5-7 leaves. The leaves are large, double-pinnate, 40-80 cm high. The terminal segments have blunt teeth, never ending in a needle-like manner. The petioles are short, densely covered with brown films.

Vegetative and spore-bearing leaves do not differ in shape, size and color. The first leaves that appear in the spring remain vegetative. Later, leaves bearing sporulation organs are formed. The sori are round, arranged in two rows along the midrib of the terminal leaf segment. IN at a young age each sorus is completely covered with a clearly visible rounded kidney-shaped veil. The cover is attached along a radial groove running from the center to the edge.

The sporangium is a round, flattened capsule shaped like a biconvex lens. Under a single-layer wall, 64 spores are formed in the sporangium. Simultaneously with the development of spores, a ring differentiates in the wall of the sporangium. The cells of the ring are located along the crest of the sporangium, surrounding it by approximately 2/3 of the circumference, that is, the ring is incomplete. The spores are dark, kidney-shaped. On the surface of their shell there are outgrowths in the form of blunt tubercles and ridges. Spores ripen in July - August.

Male shieldweed is often found in grassy deciduous and coniferous forests with moist, rich soil, as well as in shaded conditions on rocks. In the north of the republic it is rare.

Dryopteris spinulosa (Mull.) O. Ktze.

By external structure and lifestyle has many similarities with the previous knowledge.

The needle plant differs primarily in that its leaf blade in the lower part is often three-pinnately dissected. The terminal segments are oblong, with teeth elongated into a soft needle. The petioles are long, covered with light brown films. Height 30-60 cm.

The sori are covered with a shield-shaped veil attached in the center, which does not completely cover the mature sorus. The spores ripen in July - August.

A widespread fern in Karelia, found in various types of forests.

The rhizome is poisonous. Like male fern, it has an anthelmintic effect.

Three-parted holocaber - Gynmocarpium dryopteris (L.) Newm. (Dryopteris Iinnaeana C. Christens)

The fern is also called the Linnaeus fern. Its leaves are of medium size, 20-30 cm high, bright green, delicate, with thin petioles. The plate is triangular in outline, its width slightly exceeds its length, and is divided into three almost equal parts, sitting on petioles. Each part is triangular, doubly pinnately dissected.

The rhizome is thin, black-brown, intensively branches and grows, occupying significant areas.

Sori without veils, located in rows close to the edge of the segments, are always clearly separated from each other. The spores are kidney-shaped, with sparse tubercles. Ripen in July - August.

The three-parted golokuchnik is common throughout the territory of Karelia. Abundant and widespread in shady, moderately moist coniferous and deciduous forests.

Beech telipteris - Thelypteris phegopteris (L.) Sloss. (Dryopteris phegopteris (L.) C. Christens)

The plant is of medium size, reaching 30-40 cm in height. It has a long, thin rhizome, on which leaves are located singly, at some distance from each other.

The leaves are doubly pinnately dissected, oblong, with a triangular pointed apex and a spear-shaped base. The petiole is thin, equal to or as long as the plate. It is characteristic that the leaves along the veins on both sides are covered with long hairs and have brown films. The lower pair of oppositely located segments is no larger in size than the ones above them and is moved away from them; their tops are deflected downwards. The remaining segments are close together, with ends curved upward.

The sori are round, without a veil, arranged in two rows on the terminal segments. The spores ripen in July - August.

Found in damp shady forests throughout Karelia.

Female nomad - Athyriuni filix femina (L.) Roth.

It has a short, thick, oblique or almost vertical rhizome, on which numerous leaves are collected in a bunch. The leaves are large, 50-100 cm high, on petioles that are 2-3 times shorter than the blade. The leaf blade is light green, soft, oblong-elliptical in outline, double-pinnate in the upper part, and thrice-pinnate in the lower part.

The sori are oblong, straight or curved, located in two parallel rows along the midrib of the second-order segments. The veil is well developed and follows the shape of the sorus. Attached with one edge at the vein. The free edge is fringed. The spores ripen in July - August.

One of the most common ferns in Karelia, it is rare only in the northern regions. Grows in damp shady forests of various compositions, in thickets of bushes.

Decoctions of the rhizome are used as an anthelmintic. The leaves contain up to 120 mg/% vitamin C. Can serve ornamental plant for planting in shady places.

Common bracken - Pteridium aquilinum (L.) Kuhn.

Bracken has a long, dense black rhizome located horizontally in the soil at a considerable depth. It branches abundantly. The end of each branch bears one leaf. Here are located young, snail-shaped leaves that come to the surface only in the third year of their development.

The leaves of bracken do not overwinter, they are large, 50-100 cm tall. The leaf blade is leathery, light green, double-, triple-pinnate, deflected at an angle from the petiole. The petiole is grooved, long, approximately equal to the plate.

The sori are not separated from each other, but are located in a continuous narrow strip along the edge of the leaf. At the same time, the leaf is wrapped on the underside and covers them with its ciliated edge.

The structure of the sporangium, prothallus and embryo is typical of ferns. The spores ripen in August.

A common and widespread fern in southern Karelia. North of Lake Onega it gradually disappears. It grows mainly in dry pine forests on sandy soils, as well as in light small-leaved forests, along the edges, and in clearings. Often forms extensive, closed thickets.

The rhizome is a weak anthelmintic. The leaves have a peculiar smell and have anti-putrefactive and insect repellent properties. In addition, the rhizome contains up to 46 percent starch and can be used to prepare glue. It washes with water, so it can be used instead of soap if necessary. Bracken contains a significant amount of tannins. There are indications that it is toxic to domestic animals. But at a young age, bracken contains a lot of protein and, after appropriate processing, is used as food in some countries.

Common centipede - Polypodium vulgare L.

The rhizome of the centipede is creeping, densely covered with red-brown films, and has a sweetish taste. It has two rows of alternate leathery leaves on short petioles. Their height is 15-30 cm. The plate is oblong, pointed, once indistinguishable.

Sori without veils, round, placed in rows on both sides of the vein (mature ones merge). The spores ripen in July - August.

In the southern and central regions of the republic, the centipede is often found on bare and forested rocks, but does not form continuous covers.

In medicine, the rhizome is sometimes used for bronchial catarrh.

Chemical composition of the cell. Choose which structures these statements belong to. A. Long thread connected in series

amino acids –

B. The composition of the AUCG bases includes:

C. Their monomers are amino acids:

D. Not common to all types of proteins:

E. Looks like a double helix –

F. One of their main functions is catalytic -

G. Contains ribose –

H.Contains bases: ATGC

I. Carry hereditary information –

J. Their monomers are nucleotides

K. Subject to denaturation –

L. Forms a globule –

M.Were first discovered in the nucleus –

N. Contains deoxyribose –

2.nucleic acids

3.primary protein structure

4.protein secondary structure

5.tertiary structure of protein

6.quaternary protein structure

1) Indicate the features characteristic of arteries

a) the walls are thick b) the speed of blood movement is minimal c) the pressure is extremely high d) the walls are single-layer
2) indicate the features of the larynx
a) looks like a tube b) consists of cartilage 3) looks like a funnel d) at the bottom it passes into the bronchi
3) What epithelium does the gastric mucosa consist of?
4) Device for measuring the vital capacity of the lungs

Help. Very urgent. Highlight the main thing. Bed bugs belong to the order Hemiptera, in Latin hemiptera. This is the largest order among insects, they

have incomplete transformation. To date, more than 30,000 have been studied various types bedbugs, which are distributed throughout the modern globe. Hemiptera owe their name to the peculiar structure of their front wings, which have sharp differences from the hind wings. They have the appearance of transparent membranes with a small number of veins. In these insects, the fore wings, which have heterogeneities in the amount of chitinization, have turned into elytra. In bedbugs, the main part of the elytra has hard chitin, and the apical part is membranous, with veins clearly visible on it. For some species of bugs, so-called wing dimorphism has been noted, which consists in the fact that in addition to full-winged individuals with fully developed wings, elytra are also found in short-winged individuals. For example, males belonging to the pine subcortex have normally developed elytra, but they lack a second pair of wings, while females can be of two forms. There are long-winged and short-winged forms. In the case of the long-winged form, both pairs of wings have developed in the female; such a female is adapted for flight. But the short-winged individual cannot fly, since it has shortened elytra and no wings. It is much less common when bedbugs completely lose their wings.
The latter is observed in bed bug. As characteristic feature, characteristic of all belonging to this order, in addition to the structure of the elytra, is called piercing-sucking oral apparatus. It has the appearance of a proboscis, which extends from the anterior edge of the insect's head and does not merge with its prothorax. The main part of the proboscis is the strongly elongated lower articulated lip. This lip forms a deep groove on the inside. It accommodates significantly modified lower and upper jaws. They look like long thin bristles. And the top of the proboscis is covered by a relatively short upper lip.
If we talk about water bugs, then unlike beetles, their larvae are like a smaller version of the imago. They are distinguished by their lack of developed wings. In the group of water bugs there are insects that have various forms bodies. Their way of life is also significantly different.

Fern outgrowth (sexual generation): 1- archegonia; 2 - antheridia; 3 - rhizoids.

a thin green heart-shaped plate - a prothallus.

With its lower surface, the prothallus is tightly pressed to the ground thanks to rhizoids that absorb solutions of mineral salts from the soil. The fern prothallus is bisexual: on its lower surface there are female (archegonia) and male (antheridia) genital organs. The prothallus represents the sexual generation of the fern.

During rain or heavy dew, multiflagellate sperm emerge from the antheridium into the water and move towards the archegonium. This is how the process of fertilization occurs, after which a zygote is obtained - a cell with a double set of chromosomes.

Archegonia and antheridia of ferns: 1 - archegonia, I- egg; 2 - antheridia during sperm release ( With).

It germinates here, on the shoot, and forms an embryo. Growing more and more, it forms all parts of an adult plant: stem, leaf, roots. Then, sori with sporangia again form on the lower surface of the leaf of an adult plant.

Thus, the development cycle of the fern is dominated by the asexual generation, which forms sporangia with spores (the fern itself). The sexual generation (prothallus) is small in size and does not last long. Both generations exist separately, independently.

In a similar way, the reproduction of horsetails and mosses is carried out, which, together with ferns, are combined into the class of ferns.

Reproduction occurs differently in seed plants. It is not the spores that dissipate, but the seeds. However, these plants also produce spores, as well as two types of sexual reproduction cells: male and female.

Gymnosperms, such as pine and spruce, produce male and female cones. Male cones are collected in close groups at the base of the shoots developing this year. Female cones sit alone, first at the top of the shoot, and then, due to the growth of the shoot, they end up at its base.

The male cone consists of scales that sit closely on the axis of the cone. On the lower surface of the scales there are two sporangia. Inside the sporangium, a huge number of spores (motes of dust) develop through reduction division. The contents of each speck of dust consist of dense plasma and a nucleus. The dust particle is covered with a shell that forms two bubble mesh air sacs. Such a device helps the wind disperse dust particles that fall out of a burst anther.

The speck of dust grows into a male prothallus, initially enclosed within the speck of dust. At the same time, its nucleus divides and two quickly deteriorating cells and two longer-lasting cells are formed - a larger vegetative one and a smaller antheridial one. In this two-celled state, a speck of dust is carried by the wind and lands on the surface of the female cone, where the process of fertilization occurs.

The female cone consists of small covering scales, in the axils of which large fleshy seed scales develop. At the base-

Each of us has seen ferns. These herbaceous plants are widespread in the temperate climate zone. What type of fern outgrowth does it look like? You will find the answer to this question in our article.

General characteristics of the department

Ferns are representatives of higher spore plants. These are the first land plants, which are characterized by the following characteristics:

• the appearance of real tissues and organs;
• herbaceous life forms;
• reproduction using cells asexual reproduction- dispute;
• alternation of generations in the life cycle.

Of the modern species, in addition to ferns, this systematic group includes mosses, mosses and horsetails. In all these plants, the sexual and asexual generations differ in the method of reproduction and morphological characteristics. Thus, the sporophyte of a fern is a leafy plant. This is a sexless generation. But the gametophyte, the outgrowth of a fern, has a completely different shape.

Life cycle features

The plant of the asexual generation of ferns consists of a root and a shoot. On the surface we can only see the shoot itself, which changes and develops underground. It's called a rhizome. Externally, this structure really resembles an underground organ. But the rhizome is a shoot because it consists of internodes, nodes and buds.

On the underside of fern leaves, small brown tubercles can be seen with the naked eye. These are sporangia in which cells of asexual reproduction are formed. When ripe they enter wet soil. There they germinate, forming a fern outgrowth. This structure has a completely different appearance - a flat green plate. The dimensions of the growth are very small - only a few millimeters. Therefore, it is very difficult to distinguish them in the dense cover of plant thickets.

What type of fern outgrowth does it look like?

Despite its microscopic size, the structure and functions of this stage are quite complex. The photo of a fern outgrowth clearly shows that it develops separately from the plant of the asexual generation. Mostly it has wavy edges. In the middle this plate is massive. The edges are thinner, single-layer, slightly translucent.

The fern prothallus has the appearance of a heart-shaped plate, in the lower part of which dense bunches of rhizoids are formed. These structures differ from real roots in the absence of tissue. They consist of cells that are united anatomically, but each of them functions separately. Rhizoids perform the function of attaching the gametophyte to the substrate.

It is important for the development of the sporophyte that the cells of the prothallus contain chlorophyll. This ensures the process of photosynthesis and the presence of the necessary organic substances for the formation of an asexually propagated plant, which has a more impressive size.

Gametophyte development

Fern spores develop only in moist soil. Their spread occurs with the help of water, wind, insects and birds. As a result of spore germination, a plate is formed. In cross section, its size barely reaches 3 mm. The fern shoot is attached to the ground with the help of rhizoids, which also provides additional nutrition for the plant.

On the underside of this structure are the reproductive organs - gametangia. These structures also have microscopic dimensions that are even difficult to imagine. They come in two types. The male ones are called antheridia. Sperm mature in them. These are germ cells that have flagella. But the movement of sperm is possible only in the presence of water. Therefore, the presence of moisture is a prerequisite for the fertilization process in all spore plants. The female reproductive organs are called archegonia. Immobile eggs are formed in them.

This is typical for ferns. This is explained by the fact that the maturation of antheridia and archegonia occurs in different time. Therefore, gamete fusion usually occurs between different seedlings.

Sporophyte

From the fertilized egg, a plant of the asexual generation develops, which predominates in the life cycle of ferns. It is called a sporophyte. If the fern shoot has the appearance of a plate, then the asexual generation is a herbaceous plant. It has an underground rhizome. Leaves develop from vegetative buds located on it. They come in two types. Young leaves are called fronds. They are spirally twisted and by their nature are pre-shoots. Mature fern leaves are complex and spreading.

There is another significant difference between the sexual and asexual generations of ferns. The fern prothallus has rhizoids, and the sporophyte has adventitious roots.

Ancient species

Modern fern-like plants are distinguished by sufficient species diversity. Of all the spores, this group is the most numerous. This is explained by their more advanced structure. On modern stage there are more than 10 thousand species.

But the ancient ferns had a completely different appearance. They especially reached their peak during the Carboniferous period. At that time, tree ferns reached up to 40 meters in height. The width of their trunks was also impressive. It was 2 meters.

The appearance of these plants on the planet dates back to the Paleozoic era. In the course of evolution, they descended from the first land plants - rhinophytes. This was 400 million years ago. Ancient ferns became extinct due to climate change. They are the basis of a valuable fuel mineral - coal.

So, in our article we found out what type of fern outgrowth - gametophyte - is. This is a thin microscopic plate of green color. It represents the sexual generation of ferns. The shoot develops separately from the plant of the asexual generation, is capable of photosynthesis, and has rhizoids. The organs of sexual reproduction develop on it, in which gametes are formed. As a result of their merger and further development The zygote produces a fern sporophyte with a leaf-stem structure.

Reproduction and development of fern.

In summer, groups of brown sacs with spores, covered with special blankets, form on the lower surface of fern leaves. In dry, hot weather, the sacs crack and the spores are dispersed over long distances with the help of the wind. Once on moist soil, they germinate. The green thread develops first. Its cells divide and form a green, heart-shaped plate. This - outgrowth fern. Rhizoids and reproductive organs are formed on its lower side. Sperm develop in the male reproductive organ, and the egg develops in the female. In humid weather, multiflagellate sperm penetrate female organ, where fertilization occurs. The resulting zygote divides and a young fern develops from it. Thus, a fern that produces spores is a sporophyte, and a fern prothallus is a gametophyte. During life, there is a change of two generations - sporophyte and gametophyte.

7. For what reasons does a megaphilous leaf differ from a microphilous leaf? How do these sheets come into being? What departments are they typical for?

The appearance of leaves during evolution followed two paths. Higher plants inherited the leaf as an organ after the flattening and fusion of the tellomes—the systems of axes—of the branching vegetative body of the primary land plants—rhiniophytes. This idea is developed by the marphophilic theory of evolution and considers the leaf as a “flatworm”. Megaphilous leaves are characteristic of ferns as spore-bearing vascular plants. The leaf is covered with a skin with stomata on the lower surface and penetrated by veins. The cells of the main leaf tissue contain chloroplasts, in which photosynthesis occurs.

Unlike mosses and horsetails, pteridophytes are characterized by macrophilia(large leaves). In some species, the length of leaves can reach 30 m or more. Modern scientists believe that fern leaves arose as a result of the fusion and flattening of branches (telomes) of ancient ancestral forms. This hypothesis is confirmed by the presence of an apical (apical) meristem in leaves, which allows them to grow at the top. In all other plants, the apical growth of the leaf is very short, and the leaves grow from the base. The leaves of ferns are called waiami. Young fronds are curled up like a snail and covered with brown scales.

2. the appearance of a leaf as a result of superficial flattened outgrowths of the primary cortex on axial organ– tellome, led to the formation of a microphilous leaf and corresponds to the structure of the leaf of club mosses.

All shoots of lycophytes are quite densely covered with small simple leaves, the shape of which can be oval, awl-shaped, spinous, linear, or lanceolate. Such leaves are located on shoots of different species either alternately, or oppositely, or whorled. These club mosses are characterized by microphyly, i.e. small leaves. The leaves on the stem are usually arranged in a spiral and are divided into vegetative leaves (trophophylls) and spore-bearing leaves (sporophylls).

8. Draw a diagram of the evolution of the stele in Lycopods. Why does the central cylinder split?

By stele we mean a set of conductive, mechanical and parenchymal tissues limited by the pericycle.

protostele

haplostele (Greek haplos actinostele (Greek actinos- ray), having radial projections of xylem in the form of rays (on a cross section it looks like a star). During the transition to the actinostele, phloem and xylem have a larger surface of contact with surrounding living tissues, which contributes to better conduction of substances.

Types of stele of higher plants: 2 - protostele; b, c - actinostele; d - plectostele; 1 - primary cortex; 2 - endoderm; 3 - pericles; 4 - phloem; 5 - protoxylem; 6 - metaxylem;

The initial type of stele, characteristic of the most ancient higher plants - psilophytes (Rhinia), is considered to be a protostele, which has the appearance of a center, a cord, in the inner part of which there is xylem, surrounded by phloem, not sharply delimited from the primary cortex. The improvement of the structure of the stele in the evolution of plants, according to the English botanist F. Bower, followed the path of creating the most rational relationship between the volume and surface of conducting tissues, which was achieved by changing the contours of the stele and led to its division into separate cords.

In different directions of plant evolution, different types of structural organization of the stele arose. Thus, changes in the contours of the xylem caused the transformation of the protostele into an actinostele and plectostele. The actinostele, characteristic of psilophytes (asteroxylon), and of modern plants - for psilot, has a lobed outline of the cross section of the exarch xylem.

9. What are the advantages of megaspores in heterosporous plants in comparison with spores of homosporous plants?

Among the pteridophytes there are homosporous and heterosporous plants.

Most ferns form spores of the same size and structure, i.e. they are homosporous. However, a small group of aquatic ferns (Salviniaceae) - heterosporous plants.

In homosporous species, all spores are identical; they form bisexual prothlae, bearing both antheridia and archegonia. In heterosporous plants, microspores develop in some sporangia, and megaspores (macrospores) in others. From microspores, reduced male processes with antheridia grow, from megaspores, larger female processes with archegonia grow. Numerous bi- or multiflagellate spermatozoa formed in the antheridium emerge from it and penetrate the archegonium, where one of them fuses with the egg. A diploid zygote is formed. Fertilization in ferns (as well as in bryophytes) is possible only in the presence of droplet-liquid water.

10. Is it possible to say that the megasporophyll of Selagenellaceae and the seminal scales of Gymnosperms are homologous organs? Prove it.

Homologous are organs that are similar in overall plan structure, position and occurrence in the process of ontogenesis. But they differ in the functions they perform.

Selagenella belongs to the lycophytes division. This is a terrestrial herbaceous plant, 8-12 cm high. The stems are erect or recumbent. Spore-bearing spikelets develop at the top of some shoots. The leaves of the spore-bearing spikelet - sporophylls - are noticeably different from the vegetative ones. The microsporangium contains many spores. When heterosporous, the most radical reduction of the gametophyte (prothallus) - haploid and development to gigantic size sporophyte - diploid. Heterosporousness caused dioecy, i.e. dioeciousness of shoots.

Let's consider the reproduction of gymnosperms using the example of Scots pine. Porophylls are collected in cones of 2 types: male ones are represented by paniculate inflorescences, female ones - solitary. The male cone is elliptical in shape; it is formed in the axil of the scale, at the site of a shortened shoot and is a shoot with a well-developed axis, on which microsporophylls are spirally located - reduced spore-bearing leaves (homologues of angiosperm stamens). At the base of the axis there are lower leaves in the form of scales that play a protective function.

Female cones develop at the tops of young shoots. On the main axis there are small sterile scales called coverts. In the axils of these scales, large thick scales with two ovules on the upper side are formed. They are called seed scales. These are reduced spore-bearing shoots, arising in the axils of the covering scales. A female cone is a group of shortened side shoots located on a common axis. The ovules are located at the base of the seed scales. The young ovule is the megasporangium.

Thus, the megasporophyll of Selagenellaceae and the seminal scales of gymnosperms are homologues. Because they are similar in the general plan of structure, position and appearance in the process of ontogenesis, but perform different functions.

In Selagenellaceae, this is the formation of megaspores; in Gymnosperms, seed scales are a place. where ovules develop.

11. Draw a diagram of the reproduction of Selagenella and Salvinia. Point out the similarities and differences.

Spore-bearing spikelets develop at the top of some shoots. The leaves of the spore-bearing spikelet - sporophylls - are noticeably different from the vegetative ones. IN Mega- and microsporangia develop in the axils of sporophylls on a short stalk. Sporophiles bear tongues that never fall off. An important difference between Selagenellaceae and club moss is their heterosporous nature: megasporangia contain 4 megaspores,

Rice. Salvinia floating.

A – sporophyte; B – leaf. B – sporocarps; D – microsporangium with male gametophyte; D - final stages of development of the male gametophyte with 8 sperm; E – megasporangium; F - megasporangium with female gametophyte; Z – archegogy; I – megasporangium with a female prothallus and a developing sporophyte embryo; j – young sporophyte.

Sporulation organs develop on the underwater side of the shoot, on segments of submerged leaves. Sporangia are found inside sporocarps. Outwardly, they are identical in shape and size, but some contain male sporangia - microsporangia, others contain female sporangia - megasporangia. The sporocarp wall resembles the wall of a salvinia leaf. Sporangia are thin-walled, male sporangia contain 64 microspores, female sporangia contain 32 megaspores. But only one of them - the central one - is viable and can give rise to a gametophyte. When the spores mature, the sporocarps sink to the bottom of the reservoir. After their destruction, the sporangia float to the surface. Micro- and megaspores and germination form the corresponding gametophyte. Both of them germinate inside sporangia. The male one is greatly reduced, the female one is visible to the naked eye. Archegonium with a very short neck. Deeply immersed in the tissue of the prothallus. After the sexual process, the zygote differentiates into a stalk, the first leaf and the tip of the stem.

In water ferns, a reduction of the gametophyte is observed. The vegetative part of the male gametophyte is represented by 2 cells. The female gametophyte is less reduced, but still so small that a significant part of it is placed inside the megaspore. In the first phases of development, the sporophyte feeds on the green female gametophyte.

12. What is the meaning of the reduction of prothalluses (gametophytes) in heterosporous lycophytes and pteridophytes. Explain your answer.

In the evolution of higher plants, there is a gradual reduction (reduction and simplification) of the gametophyte and a predominance of the sporophyte in the life cycle. Among the reasons that determined the predominance of the sporophyte is its diploidity. Compared to the haploidity of the gametophyte, it provides a higher level of synthetic processes, and, on the other hand, recessive mutations that reduce the viability of the organism do not appear in the phenotype in the diploid state, that is, a genotypically diploid organism can be considered more “stable”.

Sporophytes of most departments of higher plants (lycophytes, horsetails, ferns) are large multicellular organisms with a complex anatomical structure and body division into organs - stems, leaves, roots (real or adventitious). When we imagine a plant of a club moss, horsetail, or fern, we usually mean its sporophyte. Sporulation organs called sporangia are formed on sporophytes. In higher plants, the sporangium is a multicellular organ with a single or multilayer wall. Inside the multicellular sporangium, educational tissue is formed - archesporium, from which, as a result of meiosis (reduction division), haploid spores are formed (sporogenesis). From spores during germination, a haploid organism emerges - a gametophyte, which is not identical to the diploid maternal organism (sporophyte). In some higher plants (mosses, horsetails, some mosses and ferns), all spores are identical in size and physiological characteristics. These are homosporous organisms. From their spores, bisexual gametophytes arise. In other higher plants, spores differ in size and physiological characteristics (microspores and megaspores), - these are heterosporous organisms.

Smaller and usually more numerous microspores are formed in microsporangia, larger and fewer megaspores are formed in megasporangia. Microspores, germinating, give rise unisexual male gametophyte, on which arise male reproductive organs - antheridia. Megaspores upon germination, they form a female gametophyte bearing female genital organs - archegonia. Heterosporousness is found in some lycophytes and ferns, in all gymnosperms and angiosperms.

Gametophyte in lycophytes, horsetails and ferns it is represented outgrowth - small (from several mm to 3 cm), not divided into organs, living for several weeks (for mosses - several years) regardless of the sporophyte. On the growths in the male genital organs (antheridia), male reproductive cells develop - sperm, which, floating in drops of water, reach the female genital organs (archegonia) and merge with the egg. Gametophytes can be monoecious, when they form both antheridia and archegonia at once, or are monoecious (with only one type of genital organs). Due to the tiny size of gametophytes, the process of fertilization in horsetails, mosses and ferns can occur even with negligible amounts of water in the form of dew drops and fog etc. Usually, with a bisexual gametophyte, sperm and eggs do not mature at the same time, which reduces the likelihood of self-fertilization.

13. Selagenellaceae. general characteristics. Features of the structure of the sporophyte in connection with living conditions. The structure of gametophytes. Biological significance diversity.

Selagenellaceae. Perennial herbaceous multiaxial plants, elongated stems bear scale-like leaves. Lateral meristems (cambium, phellogen) are absent.

The order is represented in the modern flora by the polymorphic genus Selaginella or club moss. These are terrestrial herbaceous plants, less commonly vines or epiphytes. The stems show no signs of secondary growth. In some cases, the plants do not exceed 8-12 cm, some vines up to 18-20 m. The stems are erect or recumbent. Vertical shoots extend from the lying stems. The stem is covered with a single-layer epidermis. Stomata are absent. Below the epidermis is the hypodermis, which performs epidermal and mechanical functions. Wood from scalariform tracheids, bast from sieve tubes. All roots are adventitious. Gametophytes are dioecious, small, and do not form symbiosis with fungi. The total number of species is 700. Distributed in tropical rainforests.

Selaginella are heterogeneous in external structure. Spore-bearing spikelets develop at the top of some shoots. The leaves of the spore-bearing spikelet - sporophylls - are noticeably different from the vegetative ones. IN Mega- and microsporangia develop in the axils of sporophylls on a short stalk. Sporophiles bear tongues that never fall off. An important difference between Selagenellaceae and clubmoss is their diversity : megasporangia contain 4 megaspores, microsporangia - many microspores. Having freed themselves from sporangia, micro- and megaspores germinate into favorable conditions. Male and female gametophytes develop within the boundaries of micro- and megaspore shells. Only small blades of the prothallus move outward. Archegonia develop on the blades of the female prothallus. An embryo develops from a fertilized egg. With heterosporous growth, the most radical reduction of the gametophyte (thallus) - haploid and the development of the sporophyte - diploid to gigantic sizes. Heterosporousness caused dioecy, i.e. dioeciousness of shoots.

14. Horsetail order. Features of morphology and anatomy. Signs of xeramorphic and hygromorphic organization in horsetails. Features of the structure of the epidermis and stomata. Strobili. Playback cycle. The structure of gametophytes.

Horsetails are the smallest division among the ferns. The only genus Horsetail includes 32 species, of which 17 are found in our country. Horsetails grow in swamps, meadows, forests and ponds. Widely distributed throughout the globe, with the exception of Australia and New Zealand.

Horsetails reached their greatest development in the Carboniferous period. The dead remains of tree-like horsetails of that time formed vast reserves of coal.

Modern representatives of the department are perennial herbaceous rhizomatous plants. Their stems, up to several tens of centimeters high, are divided into long internodes and nodes, which determined another name for this department - Articular. From the nodes of the ground shoot, whorls of lateral shoots extend, which are often incorrectly mistaken for leaves. The true leaves of horsetails are small scale-like, very much reduced and have no chlorophyll. They grow together, forming a tube that covers the internode. Growing side shoots they break through this pipe. The function of photosynthesis in horsetails is taken over by the stem. Its chlorophyll-bearing tissue is located in the peripheral part of the primary cortex. Cells of the epidermis and mechanical tissue of horsetails are able to accumulate silica, which gives plants increased strength. In the central part of the stem of young plants there is a core, which gradually collapses. Therefore, in mature above-ground shoots there is a cavity filled with air in the center. Based on the nature of above-ground shoots, their consistency and functional morphology, horsetail species can be divided into 2 groups. In some species, all aboveground shoots are of the same type. They are very tough, usually evergreen and develop apical strobili. Species of the second group have two types of shoots - some are spore-bearing, brownish or green, and others are vegetative, green. Shoots of both types appear in the spring, and they are more tender in their consistency and die off by winter.

At the end of the growing vegetative shoot of horsetail, under the protection of young leaf sheaths, there is an apical cell in the form of a triangular pyramid; as a result of division, ring-shaped sheath primordia appear on the stem, which retain the ability to divide, forming an intercalary meristem zone. The composition of the cell membrane of the epidermis and in other tissues, but to a lesser extent, includes silica along with cellulose. On the surface of the horsetail stem in the internode area, ribs (ridges) and hollows are visible. The number of ridges is related to the diameter of the stem.

The anatomical structure of different types of horsetails is quite similar. More or less pronounced ribs and hollows stretch along the stems. Under the epidermis in the ribs, sometimes in the hollows, less often in a ring, areas of mechanical tissue are located. Between the mechanical tissue is the parenchyma of the primary cortex, containing chloroplasts and performing the function of photosynthesis. Air cavities pass through the inner part of the cortex. The central axial cylinder is not clearly demarcated from the primary cortex; most of it lies in the core. In a young stem it consists of living parenchyma, which quickly collapses and the resulting cavity is filled with air. The presence of a large number of intercellular spaces apparently indicates that ancient species, like many modern views horsetails, lived in swampy habitats. Closed collateral bundles stretch along the periphery of the stele. Phloem consists of sieve tubes and parenchyma. In the xylem, all protoxylem and most of the metaxylem are destroyed. In their place, a narrow cavity is formed through which water moves. Remains of metaxylem are found in the form of annular or spiral tracheids. The bundles in the internodes run parallel to each other. Entering a node, the core of which is filled with parenchyma, each bundle branches into 3. The middle bundle enters the leaf, and each lateral branch of one bundle merges with a lateral branch of an adjacent bundle. The newly formed bundle enters the next internode. Thus, bundles of one internode alternate with bundles of an adjacent internode.

The stomata in the internodes are confined to areas of the epidermis that line the hollows. Leaf sheaths covering the base of each internode protect the zones of intercalary meristem. Serrated leaf blades are located along the upper edge of the vagina. The shape of the vagina, color, shape and lifespan of the teeth are an important diagnostic feature when identifying species.

The conductive system of the stem of Equisetaceae is represented by an actinostele or arthrostele, that is, a segmented stele consisting of sections of different structures alternating with each other along the stem. The conducting elements of the xylem are represented by tracheids of various types, and in horsetails also by vessels; phloem consists of sieve elements and parenchyma cells. A characteristic feature of Horsetails is the presence of peculiar sporangium-bearing structures - sporangiophores, which differ in structure from the sporophylls of other plants. Whorls of sporangiophores either form spore-bearing zones on the stem, alternating with ordinary vegetative leaves, or sit at the ends of the axes, forming pure (only from sporangiophores) or mixed (with sterile leaves) strobili.

Formed on the underground rhizome adventitious roots. Some shortened internodes of the underground shoot turn into nodules, in the cells of which starch is deposited in large quantities.

Modern horsetails are not capable of secondary thickening of the stem, so there are currently no tree-like forms among them. Large horsetails that live in tropical rainforests, although they reach a height of up to 10 m, are forced to use trees as support.

In most species, spore-bearing spikelets are formed at the top of the main shoot and sometimes on the side shoots strobes, in which they develop sporangia. Spores are formed as a result of reduction division, as a rule, have spherical shape and contain chloroplasts. All modern horsetails - homosporous plants.

Once in favorable conditions, the spore grows into a green shoot ( gametophyte) several millimeters in size. In horsetails there are bisexual, male and female prothlae. The formation of all types of growths from morphologically identical spores is the result of the so-called physiological heterospory. What type of prothallus is formed from a spore is mainly determined by the conditions external environment, in particular illumination.

Multiflagellate spermatozoa develop in antheridia, and eggs develop in archegonia. Fertilization is carried out in the presence of drip-liquid water (in rainy weather or during heavy dew). The zygote begins to divide without a rest period, forming an embryo from which a new asexual generation grows - sporophyte.

Horsetails also reproduce vegetatively - by rhizomes, forming extensive thickets.

This is a perennial rhizomatous plant found in fields and meadows. Every year from the kidneys,

15.Order Salviniaceae. General characteristics, life cycle.

The order Salviniaceae is characterized by heterosporousness and the presence of spherical sori, sitting openly on underwater leaves. It includes one genus Salvinia with 8 species of freshwater plants. Of these, 6 species are common in the tropics and subtropics, 2 species are found in temperate regions; in Russia - in middle lane, in Siberia, on Far East, in the Caucasus and Central Asia. During its long existence in the aquatic environment (salviniaceae have been known since the Cretaceous period), salvinia acquired many specialized characteristics. All types of salvinia are small ferns, up to 15-20 cm in size, living in standing or slowly flowing waters. Tropical species - perennials, and species from temperate regions are annuals. They have shoots that spread along the surface of the water and have whorled leaves. There are no roots.

In each whorl of 3 leaves, 2 leaves are floating, with a single leaf blade, and the third is submerged. Floating leaves are oval or round in shape; they are covered with a waxy coating and have papillae and hairs on the surface, which makes them non-wettable. The underwater leaf is dissected almost to the base into many thread-like lobes, densely covered with hard hairs. Carbon dioxide bubbles released during breathing are retained between the hairs, reducing specific gravity plants. The underwater leaves, with their thread-like lobes, closely resemble roots. Globular sori are formed on short petioles of underwater leaves. Thus, underwater leaves perform the functions of sporulation, water absorption and the role of a float. All parts of the plant are equipped with a dense network of air cavities. The stem contains a siphonostele with a thin cylinder of xylem; mechanical tissues are very poorly developed. Salvinia species have the ability to vegetative propagation due to the buds that can form between the leaves. The side shoots developing from the buds easily break off and give rise to new plants, as a result of which vast aquatic areas can be completely covered with salvinia. This often interferes with shipping and fishing.

The sori of floating salvinia (Salvinia natans) are spherical. In them, either microsporangia or megasporangia are located on the enlarged placenta. On the surface, the sori are covered with a two-layer indusium; its layers touch only at the base and at the very apex, and throughout the rest of the length they are separated by an air-bearing cavity, which reduces the specific gravity of the sori. Sporangia have a single-layer wall, devoid of a ring. The lining layer is the tapetum, which is formed from peripheral archesporial cells; by the time the spores mature, it blurs and becomes foamy. After it hardens, a light porous mass like foam, called massula, is formed. Massulu is immersed in disputes. In microsporangia, 64 microspores are formed, and in megasporangia, only 1 megaspore reaches full development. By autumn, the plants die off, and heavy sori, rich in starch, sink to the bottom and overwinter there. In spring, the walls of the sori rot, starch is used for spore germination, and the lungs float to the surface of the water due to the mass of the sporangium. During germination, microspores develop a male gametophyte - prothallium (prothallium); it consists of 2 vegetative cells corresponding to the vegetative body of the gametophyte. It forms 2 antheridial cells, each of which forms a highly reduced antheridium.

The antheridium has a wall of 2 cells and 1 spermatogenic cell producing 4 sperm. During germination, the megaspore forms a less reduced female gametophyte, consisting of many vegetative, i.e. prothallial cells. Under pressure from the germ, the megaspore shell bursts and the germ protrudes beyond its boundaries. The freed part of the shoot turns green, and 3-5 archegonia form on it. After fertilization, which occurs following the destruction of the megasporangium wall, an embryo develops from the zygote. Thanks to the haustorium, it maintains contact with the gametophyte for a long time. The first emerging leaf has a corymbose shape, the next 2 leaves are rounded, densely covered with hairs, and later a whorl of 3 leaves is formed.

The Azollaceae family contains 1 genus Azolla with 6 species, distributed in the tropics and temperate regions of North America. These are small, delicate ferns, similar to Jungermannia liverworts.

Salviniaceae and Azollaceae show much in common and in their origin are apparently related to the ancient extinct Hymenophyllaceae.

16. Stelar theory. The concept of a stele. The main types of stelae in the microphylic line of evolution of spore plants.

Already at the end of the last century, as a result of the works of von Mohl, de Bary and, mainly, Sachs, the idea was formed that the stem of a plant consists of three tissue systems: integumentary tissues, the main parenchyma and vascular bundles immersed in the parenchyma.

But from the standpoint of such division, it was difficult to describe and systematize the various types of stem structure, and it was impossible to formulate a clear concept of their evolutionary formation.

These difficulties were overcome Stelar theory , formulated in basic terms by the French botanist Van Thiegem. Under stele Van Tiegel designated a set of conductive, reinforcing and parenchymal tissues limited to the pericycle. Initially, this purely descriptive concept was introduced for the root, but later it was extended to the stem.

Studying different types Steral organization is of great interest for understanding the evolutionary paths of higher plants.

The most primitive type of stele is that in which the vascular tissue forms a continuous mass and the central core, consisting of xylem, is completely surrounded by phloem. This stele is called protostele . The protostele is not only simple in structure, but also represents the original type from which all other types of stele evolved in the process of evolution. It was characteristic of rhyniophytes and many other extinct forms. In modern flora, some club mosses and ferns have a protostele.

The most primitive form of protostele is haplostele (Greek haplos- simple), consisting of a central bundle of primary xylem surrounded by a cylinder of phloem. A more advanced form is actinostele (Greek actinos- ray), having radial projections of xylem in the form rays (in cross section it looks like a star). During the transition to the actinostele, phloem and xylem have a larger surface of contact with surrounding living tissues, which contributes to better conduction of substances.

In the process of evolution, the protostele gave rise to siphonostele (from Greek siphon≈ tube). The siphonostele has a tubular structure; a core appears in it. The appearance of the siphonostele made the existence of larger organisms possible. The xylem, which also plays the role of reinforcing tissue, moves to the periphery of the stem; the formation of such a tubular structure makes the stem even stronger. Various types siphonosteles are characteristic of many ferns.

Further complication of the stele is associated with the appearance of large leaves in ferns (macrophilic line of evolution). The siphonostele seems to be split into separate sections. As a result of crushing, there is dictyostele (Greek diction- network) of ferns and eustela (real stele) of seed plants. The last link in the evolution of the stem stele is atactostele (Greek A≈ denial, taktos≈ order). It is characteristic of monocotyledonous plants. It differs from eustela in the absence of cambium in the vascular bundles. The conductive bundles themselves seem to be randomly scattered throughout the entire cross-section of the slice.

Revealing significant differences between the main divisions of higher plants in the architectonics of their conducting system, Stelar theory It has great importance not only for plant anatomy, but also for knowledge of plant phylogeny in general

17. Order Centipedes. General characteristics. Morphological diversity. Life forms. Variation of the structure and location of sori and sporangia. J C.

18. General characteristics and classification of seed plants. Features of morphological and anatomical structure seed plants.

Seed plants, compared to spore plants, represent a higher level of organization, since the main germ for the spread of a species is a qualitatively new formation - seeds. The evolutionary advantage of seed plants over spore plants is that their sexual process does not depend on drip-liquid water. Thanks to this independence of seeds, plants were able to spread throughout the Earth and became a progressive group.

Unlike higher spore plants, in which the spores are unicellular, in seed plants the seeds are multicellular and contain a formed embryo and a supply of nutrients for its development.

Observed in seed plants further improvement and an even greater advantage in the cycle of sporophyte development and gametophyte reduction, the existence of which is entirely sporophyte development and gametophyte reduction.

Seed plants, which appeared about 360 million years ago, are the currently dominant group of higher plants. Seed plants are divided into 2 divisions: gymnosperms, which reproduce by seeds but do not form fruits, and angiosperms, which have seeds enclosed in fruits. Evolution proceeded in the direction of reduction of the gametophyte and further development of the sporophyte. A seed is a new organ that arose in the process of evolution for the reproduction of plants. The seed contains the embryo of the future plant - sporophyte. The embryo consists of a germinal root, a stalk, a bud and embryonic leaves (cotyledons). The embryo is protected by the seed coat and has a supply of nutrients; In contrast, in a single-celled spore the supply of nutrients is small and it quickly loses germination. The seed has adaptations for dispersal and goes through a dormant period during germination, i.e. The germination process occurs under more favorable conditions. The sporophyte gained complete dominance in the development cycle over the gametophyte. The gametophyte is extremely reduced, has lost its independent existence and is completely dependent on the sporophyte on which it is formed and formed. The sexual process in seed plants is not associated with a droplet-liquid environment. Thanks to this independence, they were able to spread over the entire surface of the Earth and become the dominant group of plants. An important progressive adaptation that eliminates the dependence of the fertilization process on the aquatic environment was the emergence in the process of evolution of a pollen tube that delivers male gametes to the egg.

Gymnosperms are an ancient group of plants that appeared in the Devonian. Gymnosperms are plants with more high level organizations than higher spores, since the means for their dispersal is the seed.

1) heterosporous plants;

2) propagation by seeds;