Despite the wide variety of ferns, none of them bloom. But the plant effectively reproduces by spores and rhizomes. From the article you will learn not only the names of ferns, but also become familiar with their growth characteristics.

Ferns are an ancient group of plants belonging to spore-bearing perennial groups. They appeared on earth back in the era of dinosaurs. Today the diversity of ferns is represented by 10 thousand species. Sizes vary from tiny to huge.

They live in ponds and deserts, in swamps and rocks, in the tropics and in the north. In the temperate zone there are several dozen varieties of ferns that have delicate feathery fronds instead of real leaves, as well as strong stems - rachis.

Video “Fern Care”

In this video, an expert will tell you how to properly care for ferns.

Main types

All the variety of ferns fits into one class. The modern classification of ferns includes 300 genera and 8 subclasses, which include more than a thousand species. Three subclasses have already disappeared from the face of the Earth, leaving only the following relevant groups:

• marattiaceae;
• grasshoppers;
• true ferns;
• Marsiliaceae;
• Salviniaceae.

Marattiaceae

During the Carboniferous period, this group was the most numerous and prosperous. Among modern maratti representatives, there are only 7 main genera, living in tropical rainforests and mountain ranges. Capable of forming dense liana thickets 4–5 m high.

The most famous are 3 of these types:

1. Marattia. Includes 60 species, reaching a height of 2 m.
2. Angiopteris. Consists of more than 100 species. The wide, thick stem has a tuberous shape and reaches 1 m in diameter. Huge large vines grow up to 5–6 m and rise regal above the ground.
3. Macroglossum. Settled in Sumatra and Kalimantan.

A characteristic feature is a paired organ with a huge amount of starch at the base of the leaves.

Uzhovnikovye

They are considered the most mysterious and unique ferns, common on all continents. The name translates as “snake tongue” for its characteristic appearance.

It is characterized by medium size (up to 40 cm), and only tropical representatives of ferns grow large (sometimes up to 4 m). For example, the pendulous grasshopper, whose drooping leaves grow to gigantic sizes.

The classification includes 3 types:

• Uzhovnik;
• Helminthostachys;
• Moonwort.

All grasshoppers are distinguished by special leaves that do not curl into a snail when budding. The spore-bearing leaves from the sterile segment have the appearance of a spikelet.

True ferns

These are the most common and numerous types of ferns. They live everywhere: in the tropics, forest areas and even deserts. Represented by both herbaceous and species. In nature and on the site there are:

• representatives of multicorns. Prefers shady, moist forests;
• The bladder is brittle. Very poisonous, a naturalist can meet it in mountain ranges;
• Common ostrich. An effective anthelmintic. Grows along rivers, in shaded forests, spruce forests;
• Female kochedyzhnik is an ornamental plant used by designers to decorate landscapes. Beautiful huge leaves grow up to 1 m;
• Common bracken. Edible variety with high levels of protein and starch.

Marsiliaceae

They belong to aquatic plants, which can be found both in reservoirs of Europe and in African lakes. The most popular is Salvinia floating. Aquarists actively plant small-leaved graceful ferns along the bottom. One of the varieties - Azolla - is small in size and looks like duckweed.

By place of growth

Ferns grow all over the globe. They feel comfortable in mountains, forests, ponds, tropical jungles and even arid areas. Many of them are cultivated and serve as decoration for arboretums, parks and greenhouses.

Kidney cover

Shady forests hide a wide variety of ground cover ferns, which are characterized by lush and abundant leaf blades with feathery fronds of dark green color and elongated shoots. They need moisture to grow comfortably.

The following varieties are widespread:

• Linnaeus' Holoculus;
• The coniogram is average;
• Robert's Holocaust;
• Phegopteris beech.

Rocky

Among the rocks, high in the mountains, you can find unusual varieties of ferns. Tender plants hold firmly to rocky and gravelly areas. Among them are:

• The bladder is brittle;
• Pharmacy scraper;
• Centipede;
• Woodsia elbe.

All representatives of this group are dry-loving. To survive in the mountains, they have dense fronds.

So, Spike Moss is a miracle fern that can survive without water for 100 years. But as soon as you lower it into the liquid, the plant comes to life and turns bright green. An amazing find for a florarium.

marshy

Swamp ferns undoubtedly deserve special attention:

• Royal Osmunda. Forms a powerful rosette-tussock of twice-pinnate fronds. Another name for the plant is Chistoust majestic;
• Phlebodium is a beautiful foliage plant, which is also called blue fern for its bluish tint;
• Telipteris marsh. It forms unusual rafts on the water surface and is a rare species;
• Onoklea sensitivea has an unusual rosette of leaves of two types, differing in shape. Floats on the surface of lakes;
• Woodwardia virginiana. A large representative that prefers swamps.

Mermen

Salvinia floating is found in water bodies of Africa and southern Europe. It is cultivated for home ponds and aquariums. On the surface of shallow lakes you can find Marsilia ferns, the fronds of which are strikingly reminiscent of clover and are edible.

Forest

Forest inhabitants include:

• Рhyllitis scolopendrium. Loves beech and coniferous forests. The arrangement of the sori resembles that of a centipede;
• Microsorum scolopendra. A stable and unpretentious variety for growing;
• Antler. Distributed in the tropics, reaches gigantic sizes;
• Brown's polygonum and bristlecone. They have thick rhizomes, hairy petioles, leathery dark green rosettes;
• Circomium. One of the rare species of the Centipede family;
• Asplenium (Bird's Nest) grows in tropical forests and is also grown in pots as a houseplant;
• Selaginella moss. Planted at home in florariums, does not require complex care, needs moisture and watering.

Thanks to their excellent appearance, ferns can decorate flower beds, alpine slides, and give a mysterious and unusual look. Since ancient times, people have adapted to using parts of various plants for medicinal, food and decorative purposes.

Ferns are ancient representatives of the flora that have dominated the surface of the globe since prehistoric geological eras. They appeared about four hundred million years ago.

Prehistoric and modern representatives

At a certain period, ferns were the dominant species of ancient flora. These plant species had enormous sizes and incredible biological diversity. Ferns in ancient times had not only herbaceous, but also woody forms.

Modern ferns are modified forms of giants from the group of spore plants that once existed on Earth. However, despite the loss of their former greatness, in certain areas they remain out of competition. Russian forests, which occupy the temperate zone, are covered in places with dense thickets formed by ostrich, bracken and other species.

Habitats

Representatives of the detachment settled all over the world. Everywhere you look in the forests of any continent, you will see ferns. Its species are ubiquitous, they have spread widely across the Earth. The widespread growth of ferns is facilitated by leaves of varied shapes, excellent ecological plasticity, and tolerance to wet soils.

The maximum diversity was observed in those ferns that chose humid tropical and subtropical regions, inhabiting damp rock crevices and mountain forested areas. In the temperate zone, shady forests, mountain gorges, and swampy areas became their abode.

Whatever the appearance of the fern, you will definitely notice the plant in both the lower and upper tiers of the forest. Some species, classified as xerophytes, scattered over the rocks and nestled comfortably on the mountain slopes. Ferns from the hygrophyte category settled in the water of swamps, rivers and lakes. Representatives from the group of epiphytes chose to live on the branches and trunks of large trees.

Description

Ferns are vascular plants. This category is a union of ancient higher and modern ferns located in an intermediate niche, on one side of which there are rhinophytes, and on the other, a group of gymnosperms.

Ferns, unlike rhinophytes, have a root system and leaves, but no seeds, unlike gymnosperms. In the Devonian era, the age of fish and amphibians, ferns, evolving, gave birth to the division of gymnosperms, which, in turn, degenerated into the order of angiosperms.

The only class Polypodiopsida, formed by eight subclasses, three of which died during the Devonian, was included in the fern division. Currently, the category is represented by 300 genera, uniting about 10,000 varieties. These spore plants formed the most extensive order.

Each fern has a number of distinctive features. The species are dissimilar in size and appearance, and their life forms and cycles are very different. However, plants have characteristic features that distinguish them from representatives of other departments.

Among them there are individuals of herbaceous and woody forms. Plants are formed by leaf blades, petioles, modified shoots, and a root system with vegetative and adventitious roots. The appearance of the fern is the same. A beautiful rosette develops above the underground rhizome, formed by curved pinnate whole-leaf or lanceolate leaves, or rather fronds.

The sizes of plants vary over a huge range: from tiny ones (no more than a few centimeters), crowded into rock crevices or wall masonry, to giant tree-like representatives - inhabitants of the tropics.

Vaii

Ferns lack true leaves. Evolutionary transformations endowed them with prototypes of leaves, looking like a system of branches laid in one plane. Botanists call this phenomenon a flat branch, frond or pre-shoot. The appearance of the fern leaf is made up of complex dissected fronds, which are smooth or pubescent, thin or leathery, light or dark green.

The preshoots, which develop from snail-shaped primordia, are similar to the leaf blades of modern flowering plants. Lacey pinnately complex plane flies are mounted on strong petioles - rachises, similar to twigs. The appearance of a fern leaf on the reverse side in mature individuals is a collection of brown dots, sporangia - containers for spores.

Varieties

The inhabitants of mountains, forests and coastal areas are ferns. The types and names of these plants are to some extent a reflection of their places of growth. Representatives of ferns are classified into forest, rock (mountain), coastal-marsh and aquatic groups. Among forest species, ground cover specimens are included in a separate subgroup. Many of the species are domesticated. They are successfully used in the formation of gardening arrangements.

forest ferns

• The common ostrich has a perfectly funnel-shaped rosette. It is formed by long (up to 1.7 meters) fronds. The appearance of the spore-bearing fern resembles a fountain. Its yellow-green leaves are similar to the ostrich feather that gives its name to the genus.
• The female kochededzhnik is characterized by a spreading tuft of short petioles covered with sparse scales and three-pinnate thin plates. It is this that gives the one meter tall plant its decorative appearance.
• A distinctive feature of the Japanese nomad is the purple color of the veins and silvery shades of the shoots.
• Chartres shield is a compact plant 30-50 centimeters high, with a dark green leaf blade with triangular-ovate or oblong outlines.
• The appearance of the spore-bearing male shield fern is determined by its hard, shiny flat fronds.
• Brown's multi-row plant has a thick ascending rhizome hidden under a powerful, dense dark green rosette of double-pinnate leaves. Long hairs and brown ovoid-lanceolate scales completely cover the short petioles, rachis and rhizome of the plant.
• Polygonal bristlecone - the owner of green, leathery, shiny pre-shoots sitting on hairy petioles from which “rags” hang.

• Among the moist, shaded rocks and depressions there is an interesting fern - centipede fern. Another name for the plant is “deer tongue.” It differs from other species in the original tongue-shaped shape of bright green leaves. On the underside, glossy solid fronds are lined with linear sori varying in length.
• When at school in a biology lesson the teacher asks the children: “Describe the appearance of a fern,” as a rule, the students talk about the most common and famous type of plant - the common bracken. Its openwork fronds do not form rosettes. They extend individually from cord-like rhizomes. The leaves, similar to flat umbrellas on a thin long handle, are familiar to many people who take forest walks.

Ground cover ferns

• Hidden among the shady forests is Phegopteris beech - a twenty-centimeter plant with dark green arrow-shaped delta-shaped leaf blades.
• Linnaeus's holocabrous plant is striking with its uniquely shaped fronds, highly branched rhizomes, densely spreading over a vast area. The appearance of a fern leaf perched on a long stalk resembles an equilateral triangle tilted horizontally.
• The pinnately dissected leaf blades with triangular outlines and thin, hard petioles of Robert's holocacia have a dark green color. The species is endowed with a thin short creeping rhizome.
• The average coniogram is characterized by such differences as thin feathery ovoid fronds. The sori located along the lateral veins merge to form continuous stripes.

Rock views

Certain species of ferns grow exclusively in the mountains, inhabiting rocks, gravel and rocky areas of the earth.

• The graceful maidenhair adiantum has an original shape of leaves that merge into an ethereal openwork cloud.
• Glossy, simple dark green flatweeds are a distinctive feature of the expressive derbyanka spicata.

• Brittle bladder is a delicate fern. Species of other plants do not have such thin and brittle petioles as those of the bladderwort, with medium-sized fronds dissected into tiny lobes.
• Woodsia elbe, capable of forming picturesque pictures in rocky areas, is endowed with yellow-green oblong-lanceolate leaves.
• The soddy rhizomes of the hairy ossicle with bare pinnate leaves, narrowed upward, are covered with films of blackish shades.
• Rocky outcrops and tree trunks became habitats for the common millipede, which has dense feathery fronds.
• The apothecary plant is recognized as the only dry-loving variety of ferns.

Coastal marsh species

• Without a doubt, the appearance of the spore-bearing fern, the crested shield fern, deserves attention. In dense, leathery, lanceolate leaves, the lobes have triangular and ovoid shapes.
• Representatives of Telipteris marshes, merging, form original rafts on the water surface.
• Royal osmunda is characterized by the formation of a powerful rosette-tussock, including dying double-pinnate fronds.
• The rosette of onoklea sensitive is assembled from two types of leaves. The fronds differ in the shape of their leaf blades.
• Sphagnum bogs are often overgrown with Woodwardia virginiana, a large plant with identical double-pinnate dark green leaves and rich brown shiny petioles.

Aquatic species

• Salvinia is a rare water-dwelling fern that needs protection. Species of aquatic plants often look completely different from their counterparts that settle in forest areas. The shape of salvinia fronds resembles water lily leaves.

• A small plant - Marsilia quatrefoil - with broadly wedge-shaped, entire-edged floating leaves and a branching rhizome has tiny sporocarps, united in 2-3 pieces, clinging to one leg at the base of the petiole. The outlines of its fronds bear a striking resemblance to clover leaves.

Ferns are a group of spore-bearing plants that have conducting tissues (vascular bundles). It is believed that they originated more than 400 million years ago, back in the Paleozoic period.

The ancestors are considered to be rhinophytes, but fern-like plants in the process of evolution acquired a more complex structural system (leaves and a root system appeared).

Signs of ferns

The following characteristics are characteristic of ferns:

Variety of shapes, life cycles, structural systems. There are three hundred genera and approximately 10 thousand plant species (the most numerous of the spore plants).

High resistance to climate change, humidity, the formation of a huge number of spores - the reasons that led to the spread of ferns throughout the planet. They are found in the lower tiers of forests, on rocky surfaces, near swamps, rivers, lakes, and grow on the walls of abandoned houses and in rural areas. The most favorable conditions for fern plants are the presence of moisture and heat, so the greatest diversity can be found in the tropics and subtropics.

All ferns require water for fertilization.. They go through two periods in their life cycle:

• Long-term asexual (sporophyte);
• short sexual (gametophyte).

When a spore lands on a damp surface, the germination process is immediately activated and the sexual phase begins. The gametophyte attaches to the ground with the help of rhizoids (formations similar to roots, needed for nutrition and attachment to the substrate) and begins independent growth. The newly formed sprout forms male and female reproductive organs (antheridia, archegonia), in which gametes (sperm and eggs) are formed, which fuse and give life to a new plant.

During the opening of the sporangia (the place of maturation of spore cells), many spores are released, but only a part of them survive, because further growth requires a moist environment and a shady area.

Ferns climbing on the ground can reproduce vegetatively; the leaves, in contact with the soil, give rise to new shoots if there is sufficient moisture.

Fern stems come in many different shapes, but are inferior in size to foliage. When the stem bears leaves at the top, it is called a trunk, and is equipped with a branching root that gives stability to tree ferns. The climbing stems are called rhizomes and can spread over considerable distances.

Ferns never bloom. In ancient times, when people did not know about spore reproduction, there were legends about a fern flower that had magical properties; whoever found it would gain unknown power.

Progressive features in the structure of ferns

Roots have appeared, they are subordinate, that is, the original root does not function further. Replaced by roots growing from the stem.

The leaves do not yet have a typical structure, this is a set of branches located in the same plane called frond. They contain chlorophyll, due to which photosynthesis occurs. Fronds also serve for reproduction; on the back of the leaf there are sporangia; after they ripen, the spores open and fall out.

Adult pteridophytes are diploid organisms.

Classification of Ferns by class

True ferns- the most numerous class. Representative male shieldweed– a perennial plant, reaches a height of up to 1 m. The rhizome is thick, short, covered with scales, and has leaves on it. Grows in moist soil in mixed and coniferous forests. Common bracken lives in pine forests and reaches large sizes. It multiplies quickly and takes root well, so it can occupy large areas if used in parks or gardens.

Horsetails– herbaceous ferns, grow from a few centimeters to 12 meters ( giant horsetail), while the diameter of the stem is about 3 cm, so in order to develop they need to use other trees as support. The foliage is modified to scales, the stem is evenly divided by nodes into internodal areas. The root system is represented by adventitious roots; the soil also contains part of the rhizome, which can form tubers (organs of vegetative propagation).

- belong to the ancient species of plants that inhabited our planet during the Carboniferous period. There is a stem, immersed in the soil to the middle, and adventitious roots. Now they are gradually dying off and are found only in tropical zones. They have huge two-tiered leaves, up to 6 meters long.

Uzhovnikovye– terrestrial herbaceous plants up to 20 cm in height (there are exceptions that reach 1.5 m in length). Representatives have a thick root that does not produce branches. Rhizome, for example, rosemary semilunatum short, does not branch, but wormseed- climbing, spreading along the ground.

– aquatic fern plants (inhabit water bodies of Africa and southern Europe), which have a root for attachment to highly moist soil. They are heterosporous; male and female gametophytes develop separately. After ripening, the adult dies, and the sori sink to the bottom, from which spores will emerge in the spring and rise from the depths to the surface of the water, where fertilization occurs. Used as plants for aquariums.

The importance of fern-like plants

The remains of ferns yielded deposits of minerals: coal, which is widely used in industry (as fuel, chemical raw materials). Some species are applied as fertilizer.

Ferns provide food and home for lower animals. They release oxygen during photosynthesis.

The beauty of plants attracts landscape designers, so they are grown as decorations. Some species can be used for food (bracken foliage).

Ferns (fern-like plants) are a division of vascular plants that occupy an intermediate position between rhinophytes and gymnosperms. This group includes modern ferns and ancient higher plants, the appearance of which on Earth occurred about 400 million years ago in the process of evolution from ancient rhinophytes. The main difference between ferns and rhinophytes is the presence of leaves and root systems, and from gymnosperms - the absence of seeds. At the end of the Paleozoic - beginning of the Mesozoic era, tree ferns occupied a dominant position among the flora of our planet. Later in the Devonian period, gymnosperms evolved from ferns, which later gave rise to the group of angiosperms.

Most living ferns are herbaceous plants, but tree ferns are found in humid tropical areas. Some ferns grow on tree trunks, and some species have become houseplants.

The department of ferns includes one class Polypodiopsida, which is divided into 8 subclasses, and the plants of three of them became extinct in the Devonian. Currently, 300 genera of ferns are known, uniting about 10,000 species. This is the largest group of spore plants. Representatives of the fern department grow almost everywhere on our planet. These plants are widespread due to the variety of leaf shapes, ecological plasticity, and good tolerance of high humidity. Ferns reach the greatest diversity in humid regions of the tropical and subtropical zones, in particular, in wet rock crevices and thickets of tropical mountain forests. In temperate latitudes, ferns grow in shady forests, gorges, and swampy areas. Some species are xerophytes and are found on rocks or mountain slopes. There are species - hygrophytes that grow in water (salvinia, azolla).

Ferns are perennial herbaceous plants. Ferns have all the organs of the plant developed - root (3), stem and leaves (1). Ferns have well developed rhizome (2). Ferns can reproduce from pieces of rhizome.

Ferns have a well-developed conducting system. Through conductive tissue, water with minerals dissolved in it moves from the roots to the leaves, and substances formed as a result of photosynthesis from the leaves enter other organs.

Ferns differ from each other in size, life forms and cycles, and some other features. But all these plants have a number of characteristic features, which makes it easy to distinguish them from plants of other groups. Ferns include herbaceous and woody forms. A fern plant consists of leaf blades, a petiole, a modified shoot and a root system, including a vegetative and adventitious root.

The fern leaf has a characteristic structure; more precisely, these plants do not have true leaves. During evolutionary transformations, ferns developed prototypes of leaves, which are a system of branches lying in the same plane. The botanical name for this is flat-branch, or frond, or pre-shoot. This preshoot looks like the leaf blade of a modern flowering plant. Clear contours of leaf blades are determined in gymnosperms that appeared later.

Reproduction of ferns is carried out by spores and vegetative methods (rhizomes, flat branches, buds, etc.). In addition, ferns are capable of reproducing sexually.

The life cycle of a fern is divided into two phases: sporophyte (asexual generation) and gametophyte (sexual generation), with the sporophyte phase being longer.

There is a sporangium on the lower surface of the leaf. When it opens, the spores fall to the ground and germinate in the form of a shoot with gametes. After fertilization, a young plant is formed. Homosporous ferns have bisexual gametophytes. In heterosporous ferns, the male gametophyte is greatly reduced, while the female gametophyte is well developed and contains nutrients for the development of the future sporophyte embryo.

If the spores fall on moist soil, they germinate, forming a plant similar to a small heart - a prothallus.

Rhizoids and reproductive organs are formed on the underside of the prothallus. Sperm develop in the male reproductive organ, and the egg develops in the female. In humid weather, multiflagellate sperm penetrate the female organ, where fertilization occurs. The resulting zygote divides, and a young fern develops from it.

The importance of ferns is less significant in human life compared to angiosperms. Some types of ferns, such as bracken, cinnamon osmunda, and common ostrich, are eaten by humans. Some types of ferns are poisonous. Many of these plants are used in medicine and the pharmaceutical industry. Ferns such as nephrolepis, pteris, kostenets are grown as indoor plants. And the fronds of shield fronds are used as a green element in floral compositions. In the tropical zone, the trunks of tree ferns are used as building material, and the core of some of them can be used as food.

INTRODUCTION

Ferns are among the most ancient groups of higher plants. In terms of their antiquity, they are second only to rhyniophytes and lycophytes and have approximately the same geological age as horsetails. But while rhinophytes have long since died out, and lycophytes and horsetails play a very modest role in the modern plant cover of the Earth; their number of species is small, ferns continue to flourish. Although now they play a slightly smaller role than in past geological periods, there are still about 300 genera and more than 10,000 species of ferns.

Ferns are distributed very widely, virtually throughout the globe, and are found in a wide variety of habitats, from deserts to swamps, lakes, rice fields and brackish waters. But their greatest diversity is observed in tropical rainforests, where they grow abundantly not only on the soil under trees, but also as epiphytes on tree trunks and branches, often in very large quantities. As a result of adaptation to such different environmental conditions, ferns developed very different life forms and a very large variety arose in external form, internal structure, physiological characteristics and size. Ferns range in size from tropical tree-like forms to tiny plants only a few millimeters long.

Several species of ferns grow on the territory of the Penza region. And the purpose of this course work is to study all types of ferns that grow in the Penza region.

General characteristics of the fern department (PTERIDOPHYTA, OR POLYPODIOPHYTA)

Features of the structure and reproduction of species of the Fern division

Like the lycophytes and segmented ferns, the pteridophytes are the oldest group, known from the Devonian period. They reached their heyday at the end of the Paleozoic and beginning of the Mesozoic era, when they were represented by a wide variety of life forms and were distributed on all continents of the globe. The largest role in the composition of the Earth's vegetation was played by large tree ferns, which were part of the coal forests. Currently, ferns number more than 10 thousand species and 300 genera.

Pteridophytes are characterized by a combination of a number of characters, the most important of which are macrophilia, the absence of a cambium and the absence of strobili. Macrophily refers primarily to the relatively large size of leaves, which are often called fronds. Unlike lycophytes and segmented ferns, the leaves of ferns have a more complex morphological and anatomical structure; they consist of a base - phyllopodium, petiole and leaf blade, often dissected many times, with a dense network of veins. The leaf blade is most characterized by long-term growth of its apex. Each leaf in the stem corresponds to a leaf lacuna (leaf gap). This set of characters reflects the synthelomic origin of fern leaves, i.e. their emergence from a system of vegetative, spore-bearing or mixed bodies, which is confirmed by paleontological data.

Living ferns are distributed on all continents, occurring in a wide variety of environmental conditions. However, the leading role both in the number of species and in the diversity of life forms belongs to the ferns of tropical and subtropical forests, where many families are in the prime of their formation. Living conditions left a significant imprint on their anatomical, morphological and biological features. Modern ferns are represented mainly by herbaceous plants, and tree-like plants make up a small number. Ferns of temperate regions, except salvinia floating(Salvinia natans) are perennial herbaceous plants with long or short underground rhizomes. In long-rhizome ferns - at the bracken(Pteridium aqualinum), Holocyta Linnaeus(Gymnocarpium dryopteris), etc. - the length of the internodes is measured in centimeters, so above the ground the leaves are located at a great distance from each other. In most ferns, a rosette of leaves is formed on short rhizomes, usually dying off in the fall, while their expanded bases remain on the rhizome for a long time, forming a dense thick cover around a rather thin stem, up to 1 cm in diameter.

In the zone of tropical and subtropical rainforests, the diversity of life forms is extremely high. There are many terrestrial species in shady forests, most of them have long creeping shoots; species with short erect shoots are less common. The smallest terrestrial ferns of the genus trichomanes(Trichomanes) have a length from 3-4 mm to 2-4 cm, and the largest species angiopteris( Angiopteris), often forming dense thickets, have tuberous stems up to 1 m in diameter. They bear leaves 5-6 m long with long strong petioles and strongly dissected leaf blades. However, epiphytic ferns are the most numerous and diverse, especially in the tropical forests of the Old World. Ubiquitous epiphytes are found on moss cushions, on tree trunks and in tree crowns. Many ground epiphytes, mainly from the family Hymenophyllaceae(Hymenophyllaceae), are in conditions of excessive moisture; their lower transparent leaves, 1-3 layers of cells thick, lack stomata and absorb atmospheric moisture over their entire surface. Epiphytes living in the crowns and trunks of trees are in conditions of moisture deficiency, and therefore have dense, leathery or heavily pubescent leaves. One of the remarkable epiphytic ferns that gives a unique appearance to the forests of the Old World - nesting asplenium, or bird's Nest(Asplenium nidus), from a distance gives the impression of huge bird's nests (Fig. 1). Its short, thick shoots are firmly attached to tree trunks and branches with the help of numerous intertwined and heavily pubescent roots. At the tops of the shoots, amazingly beautiful rosettes of leathery leaves are formed, sometimes reaching a length of up to 2 m.

Rice. 1 - Life forms of ferns: A, B - epiphytic ferns - nesting asplenium (Asplenium nidus); Platcerium (P1acerium); B - leaf vine lygodium (Lygodium); G - tree shape

The entire mass of leaves and roots is capable of accumulating humus and absorbing moisture from the atmosphere, providing both nutrition and water supply. Species of the genus are widespread in all tropical forests Platycerium, or deer antler(P1atuserium). Their short stems are also attached to the bark of trees by numerous roots. Vegetative leaves have the appearance of flat, rounded plates, which with their bases are tightly pressed to the trunk, and their tops are spaced from the stem, forming a niche in the form of a pocket. Falling and rotting bark of trees and leaves of the plant itself accumulate in it, i.e. they form their own soil. U Platycerium major(R. grande) in such a niche, more than 1 m deep, up to 100 kg of soil can accumulate; under their weight, the carrier trees are sometimes uprooted. Somewhat later, vegetative or spore-bearing leaves appear, dichotomously or palmately branched, for which the plants received the name deer antler.

Similar pocket-shaped niches can form on the flat stems of some ferns, for example the Malayan species centipedes(Po1urodium imbricatum). However, along with the highly specialized forms described, there are many small epiphytes and epiphylls belonging to the genera schizea(Schizaea) and trichomanes(Trichomanes). In some species, small leaves are covered with hygroscopic hairs, which reduce evaporation and, during humid periods, absorb moisture from the atmosphere. Other species lacking hairs are capable of entering a state of suspended animation during the driest times of the day. There are significantly fewer liana ferns, and they are less specialized than epiphytes. Some simply rest on tree trunks with their thin, long stems, while others have either curved petioles, spines on the leaves, or adventitious roots on the stems. Of greatest interest is the genus lygodium(Lygodium), which has a unique life form of a leafy vine. Roots extend along the long creeping shoot from the lower side, and on the upper side there are very peculiar, repeatedly pinnately dissected leaves in two rows; their petioles are capable of very long growth, sometimes reaching a length of 30 m. Twisting around tree trunks, they bring up leaf lobes closer to the light.

Tree ferns, which include 8 genera, are very unique. Many of them, for example Dixonia(Dicksonia), cyathea(Суаtheа), are confined to mountainous regions of the tropical and subtropical zones, where they form graceful groves.

Most tree ferns reach a height of 5-6 to 10 m; rare specimens have a maximum size of 20-25 m with a trunk diameter of 50 cm. Their trunks, as a rule, do not branch and form at the top a spreading openwork crown of feathery leaves 2-3 long m (in Cyathea up to 5-6 m). In many species, 3 categories of leaves are identified in the crown - young, with snails that have not yet unfolded, the leaves are directed upward; the middle ones are located horizontally, and the fading leaves, bending down, form a kind of “skirt”. When leaves fall, often on the stem “their bases and the lower parts of strongly scleroficated petioles remain, which cover the stem in the form of a case. In addition, roots are formed under each leaf, some of which reach the surface of the earth, while others remain aerial. Stem roots are also penetrated by sclerenchyma in bunches, which gives them greater strength. Petioles directed upwards and roots directed downwards, intertwining with each other, form a strong cylinder around the stem like an armored mesh, performing a supporting function. With significant plant heights, this turns out to be an important circumstance, since tree ferns are are essentially giant grasses.

Since ferns do not have a cambium, they do not have secondary wood; mechanical strength is achieved due to the sclerenchyma lining around the vascular bundles; only sometimes the outer cortex consists of mechanical tissue. Therefore, the outer leaf-root cylinder performs the main supporting function. As the plant ages, the base of its trunk dies and collapses, but the trunk does not fall, since it is held up by hanging roots, like on stilts. It is impossible to draw a clear boundary between herbs and tree forms. Within one species, sizes can vary from several decimeters to several meters, which is largely determined by soil and temperature conditions. Even such a short list of life forms indicates a wide morphological diversity of ferns; this applies to leaves, stems and shoots in general. The morphological characteristics of ferns often encounter terminological difficulties, since the terms and concepts developed for flowering ferns are not always acceptable for ferns. This primarily relates to the concept of rhizomes of ferns, which can change their nature during ontogenesis. In the studied species of rhizomatous ferns, the zygote, when dividing, forms 4 cells; from one the haustorium arises, from the second - the root, from the third - the leaf, from the fourth - the stem, i.e. stem, root and leaf are equivalent homologous organs of these ferns. Most often, the embryonic leaf and root are ahead of the stem in their development, so a leaf with a root at the base is formed. At the base of the petiole of the first leaf, a meristematic tubercle is formed, forming a new leaf with a root at the base. The next leaf arises from a tubercle located at the base of the petiole of the previous leaf. The bases of all newly emerging leaves and roots together form a rhizome unique to living higher plants. It is sometimes called phylogenetic, i.e. developing from leaves. However, during ontogenesis, the phylogenous rhizome is replaced by the usual one; at the same time, the stem is formed ethically and the tubercle - the growth point - begins to form a stem with the rudiments of leaves. In long-rhizome ferns, at the apex, in the immediate vicinity of the apical (apical) initial cell, a tubercle of meristematic cells is isolated. It can develop either a lateral rhizome, or a leaf, which is also indicates the homology of these organs. The apex of the rhizome of long-rhizome ferns can be covered with numerous scales or remain completely bare. In short-rhizome forms, special leaves with an underdeveloped leaf blade and a well-developed base - phyllopodium - are formed at the very top; they provide additional protection for wintering buds. Branching of a plant can be carried out not only by stem buds, but also by buds appearing on leaf petioles or on leaf blades. Often such leaf buds immediately form young rosettes, which fall off and carry out vegetative propagation; such plants are called viviparous. In some ferns, for example nephrolepis tuberiferous(Nephrolepis tuberosa) thin stolon-shaped rhizomes develop from stem buds, devoid of leaves and covered with leathery scales. Coming to the surface of the earth, they form a new rosette. In addition, tuberous lateral branches appear on the stolons, carrying out vegetative propagation.

Fern leaves - fronds - are very specific. They are most characterized by long-term growth of the apex, manifested in the formation of a cochlea (the exception is the grasshoppers), and a dense network of abundantly branching veins. The development of leaves underground often lasts several years, and above the ground is completed within 1 - 1.5 weeks. In some species, for example maidenhair(Adianthum), camptosorus(Camptosorus), the leaves exhibit a stem nature - their rachis extends into a stem-like lash and, upon reaching the surface of the earth, takes root to form a new rosette. In the Lygodium described above, the leaf rachis also closely resembles the stem in its behavior. The bases of leaves, petioles and leaf blades in many species are covered with scales, which are sometimes considered as microphylls, i.e. leaves of enation origin. The diversity of their shapes, sizes, and colors constitutes an important systematic feature. The leaf blades are even more diverse. The most typical leaves are doubly, thrice or more pinnately dissected; leaves are palmately dissected and even more rarely - dichotomously dissected. The central part of the leaf blade, representing a continuation of the petiole, is called the rachis, and the lateral lobes of the first and subsequent orders are called feathers and pinnules, respectively. Along with dissected leaves, different families have whole leaves formed as a result of the complete fusion of the lateral lobes. It is characteristic that in humid tropical forests, as a rule, small ferns have whole leaves, and all large ferns have dissected leaf blades. This, apparently, is due to the nature of tropical downpours, in which powerful streams of water pass freely through the dissected leaf blade without violating its integrity. The venation of the leaves is no less diverse, from the most primitive open to the more advanced - reticulated.

In most species of ferns, leaves combine two functions - photosynthesis and sporulation (Fig. 2), however, in many species there is leaf dimorphism - some perform the function of photosynthesis, while others only sporulate, for example, ostrich, Trichomanes. Some species of ferns (Uzhovnikov, Osmunda) have dimorphism of leaf parts, in which one part performs the function of photosynthesis, and the other part - sporulation. Paleontological material shows that all 3 types of leaves already existed in the early Paleozoic and formed independently of each other.

The development of fern roots has so far been little studied. As already noted, during the formation of the embryo, the embryonic root is formed simultaneously with the stem and leaf, while the haustorium is displaced laterally. Subsequently, in some species it develops simultaneously with the leaf, while in other species it is somewhat delayed in growth and appears later, so it gives the impression of an adventitious root.

Rice. 2 - Spore-bearing leaves of ferns: A - osmunda (Osmunda); B - grasshopper (Ophioglossum); B - ostrich (Matteuccia); G - trichomanes (Trichomanes); D - schizaeae; V. tsp - vegetative part of the leaf; sp. tsp - spore-bearing part of the leaf; V. l - vegetative leaf; s.l - spore-bearing leaf

In some species, roots may appear on the surface of the shoot in the year of its establishment, while in other species - only after 1-2 years. The roots of ferns (as well as those of clubmosses and horsetails) differ from the true adventitious roots of seed plants in that they cannot be formed on already formed parts of the shoots. Fern roots live 3-4 years. In some species, for example, nephrolepis, the roots, bending upward, are capable of turning into leafy shoots.

Analysis of the vegetative organs of ferns reveals the ability to transform one organ into another, i.e. indicates that differentiation into organs is not always strictly fixed genetically. This is in direct connection with the antiquity of ferns. The similarity of the anatomical structure of stems, leaf petioles and roots also indicates the unity of origin of all vegetative organs.

In most modern species of ferns, the stems have a dictyostele, but the course of morphogenesis varies among different species. In many studied ferns, the stem of a young plant is built like a protostele, then an ectophloic or amphiphloic siphonostele is formed, and with the beginning of the formation of leaf lacunae, a dictyostele is formed. It is a cylinder in the center of which the parenchyma of the pith is located, followed by the internal phloem, xylem and external phloem, penetrated by the parenchyma of the leaf lacunae. In a cross section, leaf lacunae are represented by medullary rays, and between them along the ring there are concentric vascular bundles with xylem in the center and phloem along the periphery. During maceration, all living tissues of the pith, medullary rays and phloem are destroyed and only xylem remains in the form of a reticulate cylinder, hence the name dictyostele - reticulate stele. Phloem is single-membered, consisting only of sieve cells. The xylem is composed mainly of scalariform and partly annular tracheids. Along with the dictyostele, some ancient species retain a protostele throughout their lives (in Lygodium, Gleichenia), an ectophloic siphonostele (in Cyathea) or an amphiphloic siphonostele (in Gleichenia species, in Dipteris). All this allows us to draw a conclusion about the direction of evolution of the stele from protostele through siphonostele to dictyostele, which is confirmed by paleobotanical material. In Permian ferns, a protostelic structure is described, in Triassic ferns it is mainly siphonostelic, and in most modern ones it is dictyostelic, in which the greatest contact of conducting tissues with living parenchyma is achieved, and, consequently, water supply is improved. Ferns reproduce mainly through spores. Most species of ferns are homosporous plants; the number of heterosporous species is small. All ferns are characterized by the absence of specialized spore-bearing shoots - strobili. In most ferns, sporangia are grouped into sori; in Marattiaceae, merging with each other, they form synangia (Fig. 3). In the most primitive species, single sporangia are located along the edges of leaves or at the tops of their blades, and each sporangium is supplied with an independent vein. This is very reminiscent of the apical arrangement of sporangia at the ends of vascularized bodies in rhinophytes.

Rice. 3 - Types of placement of sporangia and sori: A - arrangement of single sporangia: 1 - apical in relation to the leaf lobes in Davalliaceae; 2 - marginal in Trichomanes; B - location of sori: 1 - marginal in hymenophyll (Hmophillum); 2 - on the underside of the leaf of the brittle grasshopper (Суstopteris fragilis); B - synangia in marattiaceae (Magattiaceae): 1 - Angiopteris; 2 - Magattia; 3 - Christiansia; D - movement of sporangia to the lower surface of the leaf during morphogenesis in Schizea (Schizaea); sp -sporangium

In most ferns, sporangia or sori are located on the lower surface of the leaves. Most often they are confined to the main and lateral veins, less often (for example, in bracken) - near the edge of the leaf. The location of sporangia on the underside of the leaf turns out to be biologically advantageous: firstly, it provides reliable protection for sporangia during their maturation and at the same time does not reduce the intensity of photosynthesis. Secondly, a more uniform dispersion of spores is ensured; a third of them creates the possibility of greater production of sporangia on the entire surface of the leaf than just along the edge. The course of morphogenesis of spore-bearing leaves in some species of the genus Schisea shows a possible path for the movement of sporagnites to the lower surface of the leaf during phylogenesis. In the early stages of leaf development, the schizea sporangia are laid along its edges, but as a result of more rapid development of the tissues of the upper side of the leaf, its edges bend downward. As a result, they end up on the underside of the sheet. The place where the sporangium attaches to the leaf is called placenta. During evolution, the placenta grew, and it acquired an oblong or spherical shape, which increased the area of ​​possible placement of sporangia. In addition, on the placenta, sporangia are located in a certain sequence, and therefore, their maturation and opening do not occur simultaneously. The extended maturation of spores over time guarantees their more reliable distribution. An increase in the number of sporangia on the placenta is also achieved by increasing the length of the sporangium stalk. The growth of the placenta and the increase in the length of the pedicle are not correlated; these two processes occurred in different systematic groups independently of each other.

The protection of sori during their maturation is of great biological importance. In the simplest case, the sori are covered with the edge of the leaf folding downwards. In more specialized species, a special indusium blanket is formed, resulting from local growth of the placenta or surface tissues of the leaf. Based on the nature of the formation and structure of the wall of the sporangium, ferns are divided into leptosporangiate and eusporangiate ferns. In eusporangiate ferns, the sporangium arises from a group of cells and has a multilayer wall; in leptosporangiate ferns, it arises from a single cell and has a single-layer wall. Both types of sporangia were found in ancient ferns. The mechanisms for opening sporangia are also extremely diverse. In the simplest case, at the top of the sporangium there is a small area of ​​​​strongly thickened cells - a pore. When the sporangium dries, it ruptures at the contact of thin-walled and thick-walled cells. However, already in ancient ferns a so-called ring arose - a strip of thick-walled cells. In representatives of some families it occupies a horizontal position, in others it is oblique, in others it is vertical. A ring that is continuous or closed is considered primitive; more perfect - incomplete, in which part of the cells of the ring remains unthickened (the so-called mouth); a wall rupture occurs along it. An example is the sporangium male shieldweed (Driopteris filix-mas), having the shape of a biconvex lens and located on a long stalk. The single-layer wall of the sporangium consists of large thin-walled cells. Along the crest of the sporangium, starting from the stalk, there is a ring consisting of 2/3 thick-walled cells, and 1/3 is at the mouth. The cells of the ring have thickenings on three walls - on two radial and on the inner - tangential. When the cells of the ring dry out, they lose water, which leads to a decrease in their volume. The large adhesive force pulls the thin outer tangential wall inside the cell, and it bends, attracting the radial walls towards each other. This leads to a decrease in the circumference of the ring and creates a large tension in the orifice area. Happening

rapid rupture of the sporangium wall, and the ring turns outward, scattering spores. As the water evaporates further, the thin tangential wall touches the inner one, the adhesive force disappears, and the ring springs back to its previous position, scattering the remains of the spores.

Representatives of primitive families have large, few sporangia containing a large number of spores (8-15 thousand). In advanced families, numerous sequentially occurring sporangia are small, usually containing from 64 to 16 spores. This ensures the autonomy of sporangia and increases the reliability of spore preservation.

Spores can remain dormant from several weeks to several years and even decades. For their germination, moisture, positive temperatures, a certain acidity of the soil, intensity and quality of light specific to each species are required.

There are different options for spore germination and the course of gametophyte morphogenesis, which turn out to be characteristic not only of individual families and even genera. Therefore, when classifying ferns, some pteridologists are based on the characteristics of the development and structure of gametophytes.

The gametophytes of most homosporous ferns lead a terrestrial lifestyle, carrying out autotrophic nutrition. Their lifespan, as a rule, is calculated at several months, and only in some of the most primitive species gametophytes live for several years (sometimes up to 10-15). With a general trend towards a reduction in life expectancy, the gametophytes of some species of ferns have become secondary perennials. The formation of the gametophyte largely depends on the spectral composition of the light - in blue rays there is a long-term growth of the thread, and in red rays lamellar forms are formed. Initially, the growth of a single-layer plate is carried out due to the marginal cells, and then at the top of the thallus one initial cell separates, which forms the apical meristem. In this case, the plate (several millimeters in size) takes on a heart-shaped shape with a cushion-shaped central part. A physiologically active meristem secretes a specific hormone, close to growth hormones, antheridiogen; it stimulates the formation of antheridia on nearby shoots. On the underside of the plate at its base, antheridia develop among numerous rhizoids. A little later, at the top of the plate, archegonia form on a multilayer cushion. The non-simultaneous development of antheridia and archegonia promotes cross-fertilization. As experiments have shown, with a large accumulation of shoots, the concentration of antheridiogen in the environment increases so much that on newly formed young gametophytes antheridia can appear very early, sometimes at the stage of a 2-3-cell filament. A high concentration of antheridiogen stops further development of the gametophyte, and therefore the formation of archegonia, so it remains unisexual male. In the absence of antheridiogen, under favorable conditions, rapid development of the prothallus occurs, culminating in the phase of a heart-shaped plate with a well-developed meristem. On the outgrowth, bypassing the stage of formation of antheridia, archegonia are formed, i.e. it turns out to be a same-sex female. With a weak influence of antheridiogen, the gametophyte goes through all stages of morphogenesis, first forming antheridia and then archegonia - a bisexual prothallus appears. In nature, the mutual influences of gametophytes on each other are more complex and difficult to observe.

The described type of gametophyte morphogenesis, although the most common, is not the only one. In Schizaeans and some hymenophylls, the prothalluses retain an abundantly branching filamentous shape throughout their entire lives, so antheridia and archegonia appear in them without a visible pattern on the lateral branches. In Marattiaceae, green shoots measuring 2-3 cm are multilayered, fleshy, and live for several years. In the Uzhovnikovidae, some Schicheaaceae and Zheicheniaceae, the tuberous or worm-shaped gametophytes lead an underground lifestyle, feeding mycotrophically, so they are colorless. However, when they get to the surface of the earth, they turn green, from which we can conclude that their underground existence is secondary. The antheridia of primitive families are large, with many spermatozoa, while in more advanced representatives they are small, containing up to 32 spermatozoa. The archegonia of all ferns are of the same type, immersed in the gametophyte tissue. The progress of zygote germination and the formation of a young plant are described above.

There are deviations from the typical development cycle of ferns. Sometimes the sporophyte can develop apogamously, i.e. without fertilization, from one or a group of vegetative cells of a haploid gametophyte. In this case, the sporophyte turns out to be haploid, and spores are formed without reduction division. In other cases, the gametophyte arises aposporically not from a haploid spore, but from the dishuid tissues of the sporophyte (from sporangium cells, leaves, etc.), i.e. it turns out to be diploid. In this case, the diploid egg develops into a new sporophyte without fertilization.

Vegetative propagation is widespread among ferns. It is often carried out with the help of brood buds that appear on leaves, stems and roots. In the latter case, the roots, bending, emerge to the surface of the earth and form a bud at the top. Often, long lashes develop on the leaves and stems, on which buds appear.

The classification of the entire department of fern-like and especially extinct forms is experiencing significant difficulties. It can be based on various features - the anatomical and morphological structure of the vegetative organs of the sporophyte, the characteristics of sporulation (the structure of sporangia and their placement), the nature of the formation and structure of gametophytes. The ancient extinct groups of ferns, the protoferns, underwent the greatest revision. Taxa such as aneurophytes(Aneurophytopsida) and archaeopteris(Archaepteridopsida), based on the presence of pronounced secondary xylem and the presence of bordered pores on the walls of punctate tracheids, are classified as proto-gymnosperms(Progymnospermae). The classification of living ferns is based on the structure of the sporangium wall in combination with a number of morphological characters.

The classification of ancient ferns is further complicated by the fact that in the Paleozoic there were synthetic species that combined the characteristics of various taxa. Recombination of characters, which was generally characteristic of most Early Paleozoic plants, makes the identification of taxa conditional.