Bryophytes. Comparative analysis of the life cycle of mosses (cuckoo flax) and club mosses (annual club moss) What does a moss box grow from

09.05.2023 | Construction

Tests

620-1. The accumulation of what group of plants contributes to waterlogging of the soil?
A) lycopsform
B) horsetail
B) mossy
D) ferns

Answer

620-2. The stem with leaves in the process of evolution first appeared in
A) algae
B) mossy
B) horsetail
D) ferns

Answer

620-3. Mosses represent a dead end branch in plant evolution because
A) more highly organized ferns originated from them
B) they did not give rise to more highly organized plants
C) more highly organized horsetails originated from them
D) they evolved from unicellular algae

Answer

620-4. What are the characteristics of mosses?
A) adventitious roots develop from the stem
B) spores are formed in a box
C) they have no escape
D) pollination precedes fertilization

Answer

620-5. Mosses develop from spores
A) a box on a leg
B) seed
B) green thread
D) sprout

Answer

620-6. The adaptability of sphagnum moss to life in conditions of excessive moisture is manifested in the presence of
A) rhizomes with adventitious roots
B) cells with chloroplasts
B) dead cells
D) rhizoids

Answer

620-7. Representatives of which department of the plant kingdom are shown in the figure?

Answer

620-8. What plants belong to the Bryophytes department?
A) living on land and reproducing by seeds
B) leafy, without roots, reproducing by spores
C) all plants in wet habitats
D) all herbaceous plants

Answer

620-9) What adaptations to the absorption of large amounts of water appeared in the process of evolution in mosses?
A) rhizoids - outgrowths on the stem
B) large dead cells
B) spore boxes
D) cells of thin integumentary tissue

Answer

620-10. In green mosses, unlike algae,
A) cells have large and small nuclei
B) fertilization occurs in the presence of water
C) the thallus is divided into tissues and organs
D) sexual and asexual reproduction

Answer

620-11. What division of higher plants does the plant shown in the picture belong to?

A) angiosperms
B) Gymnosperms
B) ferns
D) Bryophytes

Answer

620-12. How are bryophytes distinguished from other plants?
A) in the process of their development, alternation of generations occurs
B) reproduce by spores
B) have leaves, stem and rhizoids
D) capable of photosynthesis

Answer

620-13. Ferns, unlike green mosses, have
A) rhizoids
B) roots
B) leaves
D) stems

Answer

620-14. From spores of green moss cuckoo flax develops (s)
A) a growth in the form of a green plate
B) pregrowth in the form of green threads
B) plants with leaves
D) seeds of the future plant

Answer

620-15. Higher plants have no roots
A) Tsvetkov
B) conifers
B) moss
D) Ferns

Answer

620-16. Ferns are much more widespread on Earth than mosses, since they
A) have a developed root system and multiply more efficiently
B) appeared in the course of evolution earlier and managed to better adapt
C) are widely grown by man for their needs
D) successfully distributed by various animals

Answer

620-17. Mosses have the simplest structure among higher plants, since
A) they have no roots
B) their stem is unbranched, with narrow leaves
C) they form organic substances from inorganic
D) they have air cells

Answer

620-18. Why do mosses represent a dead end in plant evolution?
A) they have not mastered the ground-air habitat
B) they evolved from algae
C) they do not have roots and reproduce by spores
D) they did not give rise to more highly organized plants

Answer

620-19. What department of the plant kingdom is represented in the picture?

A) ferns
B) Gymnosperms
B) Lycopsoid
D) Mossy

Answer

620-20. Which group of organisms includes green plants that do not have roots, reproduce by spores, in the life cycle of which the sexual generation predominates?
A) bryophytes
B) ferns
B) gymnosperms
D) lycopsform

Comparative analysis of the life cycle of mosses (cuckoo flax) and club mosses (annual club moss)

Life cycle of the cuckoo flax

Kukushkin flax - Polytrichum commune - is a characteristic representative of deciduous mosses. The body of the cuckoo flax moss is dissected into a thin, rounded, reddish stem and narrow, green leaves. Roots are absent, they are replaced by well-developed rhizoids. Compared to other types of mosses, cuckoo flax has a great height; it reaches a height of 20-40 cm.

Cuckoo flax reproduces by spores. He has a well-defined generational change. This is a dioecious plant. The reproductive organs are formed at the top of the stems.

Male specimens of cuckoo flax have a characteristic arrangement of leaves at the top of the stems. Larger leaves are formed here, they sit much denser in the form of a rosette and have a reddish color. By this arrangement of leaflets, it is easy to recognize male specimens. Antheridia are formed on the expanded upper part of the stem. Antheridia are somewhat elongated, they develop spermatozoa with two flagella.

Archegoniums are flask-shaped, located at the top of the stem of a female plant, which, unlike the male, does not end with a rosette of red leaves.

Fertilization occurs in early spring, when low places where mosses grow are flooded with water. One of the spermatozoa penetrates to the egg through the mucous canal of the neck of the archegonium and fertilizes it. A sporophyte grows from a fertilized egg in the form of a long thin stalk ending in a box of complex structure. The sporophyte of the cuckoo flax has a special name - sporogony. The sporogon box has an elongated cap with a pointed end. Outwardly, it is similar to the cuckoo, hence the name of this moss.

The cap is a calyptra, this is the upper modified part of the archegonium. Under the cap is the lid of the box. Inside the box there is a central rod - a column, a spore sac is attached to it, in which spores develop. Initially, the spores are connected into tetrads, i.e. four pieces together.

Before maturation, tetrads break up into separate spores. At the box, the cap falls first, then the lid. The box ends with cloves, in dry weather they bend outward and thereby open the way for mature spores.

The spore, falling to the ground, in the presence of a sufficient amount of moisture, germinates, forming a protonema y, or pregrowth. Protonema consists of thin branched filaments filled with chlorophyll.

Protonema, growing, forms an apical bud, from which adult plants of cuckoo flax grow, and some protonema form only male, and others only female plants.

Although there is no external difference between the spores, they are physiologically different. After fertilization, the egg grows into an asexual generation in the form of a sporogon growing on the female gametophyte. In cuckoo flax, the gametophyte predominates in size over the sporophyte.

In moss cuckoo flax, there is a different need for environmental conditions on the part of the sporophyte and gametophyte. The sporophyte (sporogon) of the cuckoo flax growing on the female gametophyte has a clearly expressed adaptability to life in the air, and it does not need water, since it receives the necessary amount from the gametophyte.

The dry environment prevents spores from germinating in the box. The sexual generation of this moss cannot live without free water, since it does not yet have roots and therefore receives the bulk of it not from the soil, but from the atmosphere.

Free water is necessary for the sexual generation of cuckoo flax and for the implementation of the sexual process, for the movement of spermatozoa.

Moss cuckoo flax is a perennial plant. After release from spermatozoa, male specimens do not die; they continue to grow, and the next year, antheridia form again at the top of them.

Female specimens do not die either, after dispersal of the spores, the sporogon falls on them, and the plants continue to grow, and the following spring, archegonia again form on the top of their stalk.

Scheme of the development cycle of cuckoo flax. Explanations in the text

Development cycle of green moss Kukushkin flax. Explanation in the text

Department of the most low-organized higher spore plants, uniting about 25 thousand modern species. Mosses are characterized by:

© antheridia (male organs of sexual reproduction) are single-layer sac-like formations on a stalk, filled with sperm cells, from which biflagellate spermatozoa are formed; archegonia (female organs of sexual reproduction) - bottle-shaped structures, consist of an abdomen containing an egg, and a neck;

© The sporophyte consists of a box in which the sporangium develops, a stalk (in some mosses it may be absent) on which the box is located, feet, or haustoria, which provides communication with the gametophyte;

Kukushkin flax is one of the most widespread representatives of the subclass Green mosses (Fig. 66). It grows in wet places, in swamps, swampy forests. This is a perennial plant, reaching a height of 15-40 cm. It grows in groups, forming large cushion-like sods.

The "stem" of moss is upright, unbranched. In the center of the "stem" there are more elongated (elongated) cells corresponding to xylem and phloem. "Stem" densely covered with narrow linear-lanceolate "leaves". They are made up of several layers of cells. At the base of the stem, multicellular filamentous rhizoids develop - analogues of roots.

Kukushkin flax belongs to dioecious plants (Fig. 67). On the male gametophyte, between the barren reddish (or yellowish) "leaves" that form a rosette, there are male genital organs - antheridia, in which biflagellated spermatozoa are formed. Antheridia look like oblong or rounded sacs on a stalk. On the female gametophyte, between the upper internodes, the female reproductive organs, the archegonia, are formed. An egg develops in the abdomen. Inside the neck

located

are tubular cells. Like archegoniums, antheridia are located at the top of the plant among barren leaves. When the archegonium matures, the cervical and abdominal cells become mucilaginous, and in their place a narrow channel is formed through which spermatozoa can penetrate to the egg. Fertilization occurs in rainy weather, since an aquatic environment is necessary for the movement of spermatozoa. It is assumed that spermatozoa have a positive chemotaxis to the contents of the archegonium mucus. Spermatozoa, moving through the water, penetrate into the archegonium, in which one of them merges with the egg. The zygote is the initial stage of the sporophyte and contains

diploid set of chromosomes. A few months later, a sporophyte germinates from the zygote. It is located at the top of the stem of female moss plants. The sporophyte of the cuckoo flax consists of a haustorium, a stem, and a capsule. Gaustoria (suction cup) serves to penetrate into the body of the gametophyte. The sporophyte is completely dependent on the gametophyte. At the top end of the box before ripening is a cap. It develops from the abdominal wall of the archegonium. Under the cap is the lid of the box. In boxes in sporangia, spores are formed by meiotic division. Therefore, spores have a haploid set of chromosomes. All spores are morphologically identical (isospores).

After maturation, the cap and operculum fall off and the spores are easily dispersed by the wind. Under favorable conditions, the spore germinates into a thin branching green thread - protonema, or prejuvenile. Buds are formed on the protonema, from which gametophytes develop - adult moss plants of any one sex, having a haploid set of chromosomes.

Sphagnum moss is a small plant (up to 15-20 cm) of a whitish color with a stem branching at the top, densely covered with narrow long leaves (Fig. 68). It usually grows in dense sods.

The stem of an adult plant does not have rhizoids. It grows annually at the top, while its lower part constantly dies off. The compressed layers of dead sphagnum form peat deposits.

The core of the stem is filled with parenchymal cells, which are adjoined by lignified cells, which give the stem strength. Outside, it is covered with 1-3 layers of dead cells, the shells of which are permeated with holes (through pores) through which water is absorbed.

Sphagnum leaves are ovoid, without midrib. They are formed by one layer of cells of two types:

Antheridia and archegonium are formed by lateral branches at the top of the stem. Fertilization of eggs by biflagellate spermatozoa occurs in the presence of water. A sporophyte develops from the zygote, consisting of a round box with sporangia and a small stem.

By the time the spores mature (as a result of meiosis), the upper part of the stem elongates and the bolls rise above the leafy part of the stem. The lid of the box separates and the spores disperse. Once in favorable conditions, the spores germinate into a single-layer lamellar protonema, on which buds appear, giving rise to new moss shoots.

Sphagnum is four times more hygroscopic than cotton wool and contains a substance - sphagnon, which has an antiseptic effect. This makes it possible to use sphagnum as a dressing.

The meaning of mosses

Bryophytes in nature often settle on such substrates and in such habitats that are inaccessible to other plants. In this case, they act as pioneer vegetation, playing an important role in soil-forming processes. Bryophytes play a significant role in the regulation of the water balance of the land. They regulate the evaporation of moisture from the soil. In the meadows, mosses prevent the seed renewal of grasses, in the forests - the germination of tree seeds. By accumulating water, mosses cause waterlogging of the soil. Sphagnum and green mosses are the main peat formers. The presence of moss cover is one of the main stabilizing factors in permafrost conditions.

The economic value of mosses is small. Animals do not eat moss. Peat is used as fuel, bedding for pets, fertilizer. By dry distillation of peat, methyl alcohol, saccharin, wax, paraffin, paints, etc. are obtained. Peat is used to make paper and cardboard. In construction, peat is used as a heat-insulating material. Peat also has medical significance.

Chapter 8
(Lecopodiophyta)

At present, this department of higher spore plants unites about 1 thousand species. For lycopsids it is characteristic:

mostly tropical plants;

The club moss grows mainly in the forest zone, especially in coniferous forests.

This is an evergreen herbaceous perennial plant with a creeping stem reaching a length of 3 meters (Fig. 69). In the central part of the stem there is a vascular bundle in which the xylem is surrounded by phloem. In the peripheral part of the stem, a mechanical tissue is developed, covered on the outside by the epidermis.

In the internodes, the stem takes root with the help of thin adventitious roots. From the main stem creeping along the ground, dichotomously branching shoots up to 25 cm high depart vertically upwards. The surface of the stem is densely covered with spirally arranged small lanceolate-linear leaves.

In the middle of summer, in adult plants, club-shaped spore-bearing spikelets form on the lateral shoots of the stem, each of which consists of an axis and leaflets sitting on it - pointed sporophylls. At the base of the sporophyll on its upper part is a kidney-shaped sporangium, in which haploid spores are formed. Under favorable conditions, a haploid gametophyte develops from spores within 10-20 years - a small whitish (about 2 cm in diameter) growth, deepened into the soil and attached to it by rhizoids. The growth enters into symbiosis with the fungus and lives as a saprophyte. On the upper side of the outgrowth, archegonia and antheridia are formed, immersed in the tissue of the outgrowth. The biflagellate sperm fertilizes the egg and a zygote is formed, from which the embryo develops. It is introduced into the tissue of the gametophyte and feeds at its expense. Only after the formation of roots does it pass to an independent existence and give rise to a new sporophyte - the asexual generation of the club moss.

The value of clubs

The economic importance of club mosses is small. Animals usually do not eat them. Some types of club mosses contain a poison similar in action to curare poison. Club spores, or lycopodium, - the finest light yellow powder, velvety, greasy to the touch - is used when sprinkling pills, as baby powder (natural talc), sometimes in industry for shaped casting for sprinkling models. Badren club is used to obtain yellow dye for wool, and double-edged club is used to obtain green dye.

Chapter 9
(Equisetophyta)

The department of higher spore plants, which currently includes only one genus, represented by 25 species. Horsetails are characterized by:

the leaves are strongly reduced, look like brown scales, whorled at the nodes of the shoots;

© sporangia in groups (8-10 each) are located on modified spore-bearing lateral shoots that form spore-bearing spikelets that develop on the tops of assimilating or on specialized spore-bearing chlorophyll-free shoots;

A widespread plant in the temperate zone, often found on sandy slopes, fallow lands, arable land, in crops, and in meadows. This is a perennial herbaceous erect plant up to 50 cm high (Fig. 70). The underground part of the horsetail is a thin, long, jointed, branching rhizome with nodules in which starch is deposited. Adventitious roots extend from the nodes of the rhizome in bunches.

In early spring, gray-pink, non-branching, chlorophyll-free spore-bearing shoots grow from the rhizome, on the top of which they develop spore-bearing spikelets. In sporangia, dark green spherical spores develop, in which, as they mature, spirally twisted ribbon-like outgrowths form - elaters. They provide adhesion of spores into small loose lumps. This facilitates the spread of spores, during the germination of which a whole group of growths is formed, which facilitates fertilization.

After sporulation, spring shoots die off and later they are replaced by summer vegetative shoots. These shoots are jointed, branched, lateral branches are arranged in whorls. Small scaly leaves form tubular sheaths at the stem nodes. .

Once in favorable conditions, disputes germinate. Horsetail growths are small green cushion-shaped plants with lobed outgrowths. On male growths with antheridia, polyflagellate spermatozoa are formed. Female growths have a more dissected shape. They develop archegonia, in which the maturation of eggs occurs, and then fertilization and the formation of a zygote. The female germ ensures the germination of the embryo, from which the sporophyte gradually develops.

The value of horsetail

Most horsetails are inedible, but some types of horsetails (horsetail) are used as animal feed. It can also be poisonous in some areas. It is also used in medicine as a hemostatic and diuretic for edema. Sometimes starchy tubers and young spore-bearing spikelets are used for food. Horsetail is a pernicious weed. Marsh horsetail, riverine horsetail, oak horsetail are poisonous plants. The stiff stems of wintering horsetail can be used as an abrasive material.

Chapter 10
(Polypodiophyta)

Department of higher spore plants, uniting about 12 thousand modern species. Ferns are characterized by:

in the bark of the stem there is a mechanical tissue, in the center - several concentric vascular bundles; the xylem formed by tracheids is surrounded by a phloem of sieve cells without companion cells;

whole leaf differentiated into petiole and leaf blade; in the vast majority of ferns, the leaves are pinnate, having a petiole continuing into the rachis - the axis of the leaf, on which the feathers are located; often leaves combine the function of photosynthesis and sporulation;

male shield

One of the most widespread species of ferns in Europe (Fig. 71). It grows mainly in shady forests. The sporophyte is a large perennial herbaceous plant up to 1 meter high. The rhizome is powerful, abundantly covered with the remnants of petioles of past years and rusty-brown scales. Thin adventitious roots depart from the lower part of the rhizome. The leaf blade is doubly pinnate. For two years, the leaves develop in buds underground, and only in the third year in the spring they appear above the soil surface, and die off by autumn. Young leaves are twisted in the form of snails and grow with their top for a long time, gradually unwinding.

On the lower surface of the leaves along the middle veins, sporangia are formed by autumn, collected in sori. As a result of meiotic cell division of sporogenic tissue, haploid spores are formed. After maturation of the spores, the sporangium wall ruptures, thereby ensuring the spread of the spores.

Once in favorable conditions, the spore germinates and, from it, a gametophyte is formed, which has the form of a heart-shaped plate 1.5-5 mm long. The overgrowth is single-layered and only in the middle part is multi-layered. On the lower side facing the ground, a large number of rhizoids are formed, located closer to the pointed part of the plate. There are also archegonia and antheridia. The archegonia are located on the thickened part of the growth, closer to the heart-shaped notch, and the antheridia are closer to the pointed part, often among the rhizoids. Ribbon-like polyflagellated (several tens) spermatozoa are formed in the antheridia. Once in the water, they rush to the archegonium and penetrate through the neck into its abdomen. This is where the egg is fertilized and the zygote is formed. The embryo begins to develop in the archegonium. Until the formation of a green leaf and its own roots, it depends on the gametophyte.

The meaning of ferns

Ferns are an important component of many plant communities, especially in tropical, subtropical, and northern (mainly deciduous) forests. Many ferns are indicators of different soil types. Some types of ferns are used in medicine as an anthelmintic, to treat open wounds, coughs and sore throats. Azola species are used as a green fertilizer that enriches the soil with nitrogen. Some ferns are used in decorative floriculture.

seed plants

Bryophyte, general characteristic. If the lower plants (algae) lacked tissues and organs, then mechanical, integumentary and conductive tissues appear in the psilophytes of the Silurian period of the Paleozoic in the air, providing the possibility of life in the air. The appearance of tissues led to the appearance of higher land plants, the most primitive group among which are mosses. Bryophytes and vascular plants are thought to have evolved independently from different groups of green algae. The relationship of green algae and higher plants is confirmed by the same set of photosynthetic pigments and the accumulation of nutrients in plastids, and not in the cytoplasm of cells, as in other groups of algae.

Bryophytes, like algae, have no roots, their function is performed by filamentous outgrowths in the lower part of the stem - rhizoids. They absorb water weakly, water is captured by the entire surface of the body, so they prefer habitats with high humidity and mossy life forms - annual and perennial herbaceous plants.

The main feature that distinguishes moss plants from higher spore plants is the predominance of a haploid gametophyte in the life cycle, on which a diploid sporophyte develops. The “stem” and “leaves” of mosses are not real stems and leaves, these are gametophyte formations, the sporophyte (pedunculated box) develops on the gametophyte and is completely dependent on it. In all other higher vascular plants, the diploid sporophyte dominates in the life cycle, and haploid gametophytes are increasingly reduced.

Conductive tissues are the most primitive among all higher plants; true xylem and phloem are absent. Only the most complex bryophytes developed cells resembling the conductive tissues of xylem and phloem.

Class Leafy mosses. Kukushkin flax. Kukushkin flax is one of the most widespread representatives of the subclass Green mosses (Fig. 66). It grows in wet places, in swamps, swampy forests. This is a perennial plant, reaching a height of 15-40 cm. It grows in groups, forming large cushion-like sods. The "stem" of moss is upright, unbranched. In the center are more elongated cells corresponding to xylem and phloem. "Stem" densely covered with narrow linear-lanceolate "leaves". They are made up of several layers of cells. At the base of the stem, multicellular filamentous analogues of roots develop - rhizoids.

Kukushkin flax belongs to dioecious plants (Fig. .). On the male gametophyte, at the top, between the reddish "leaves" that form a rosette, are the male genital organs - antheridia in which biflagellated spermatozoa are produced. Antheridia look like oblong or rounded sacs on a stalk. On the female gametophyte, female gametangia (genital organs) are formed - flask-shaped archegonia. The ovum develops in the abdomen of the archegonium. Like antheridia, archegonia are located at the top of the plant. When the archegonium matures, the cervical and abdominal cells become mucilaginous, and in their place a narrow channel is formed through which spermatozoa can penetrate to the egg. Fertilization occurs in rainy weather, since an aquatic environment is necessary for the movement of spermatozoa.

Spermatozoa have a positive chemotaxis to the contents of the mucus of the archegonium, moving through the water, penetrate into the archegonium, in which one of them merges with the egg.

A few months later, a sporophyte germinates from the zygote. The sporophyte of the cuckoo flax is composed of haustoria, legs and boxes. Gaustoria (suction cup) serves to penetrate into the body of the gametophyte. At an early stage, the sporophyte is green and capable of photosynthesis, later it turns yellow, then it turns orange and finally brown and completely passes to nutrition at the expense of the gametophyte. At the upper end of the box before ripening is a cap, calyptra. It develops from the abdominal wall of the archegonium and remains haploid. In boxes, spores are formed by meiotic division (spore reduction). All spores are morphologically the same, but physiologically different.

Peat moss sphagnum. More than 300 species of the only genus Sphagnum, distributed mainly in the north of Eurasia and America, belong to sphagnum mosses. Here they occupy vast areas, being the main formers of peat bogs.

Sphagnum moss is a small plant (up to 15-20 cm), whitish in color, the lateral shoots of which are densely covered with narrow long leaves (Fig. 68). It usually grows in dense sods. The stem of an adult plant does not have rhizoids. It grows annually at the top, while its lower part constantly dies off. The compressed layers of dead sphagnum form peat deposits.

Sphagnum leaves are ovoid, without midrib. They are formed by one layer of cells of two types: narrow, long, living, containing chloroplasts - assimilating, forming, as it were, a grid and wide dead hyaline aquifers cells with spiral thickenings, located between the living.

Dead cells have holes, pores and are able to accumulate and retain a large amount of water (25-37 times their weight).

Sphagnum is a monoecious plant, antheridia and archegonia are formed on lateral branches in the upper part of the stem. Fertilization of eggs by biflagellate spermatozoa occurs in the presence of water.

From the zygote develops a sporophyte, represented by a round box. The haustoria of the sporophyte grows into the support of the gametophyte tissues - the false leg.

By the time the spores mature (as a result of meiosis), the bases elongate and the bolls rise above the leafy part of the stem.

In humid weather, air penetrates through the stomata, when the box dries up, the stomata close, the pressure in the box rises, and with a distinct pop, the lid breaks off, and a cloud of spores rises above the box. Once in favorable conditions, the spores germinate into a single-layer lamellar protonema, on which buds appear, giving rise to new moss shoots.

Sphagnum is four times more hygroscopic than cotton wool and contains a substance - sphagnum, which has a bactericidal effect. In addition, sphagnum not only swamps, but also acidifies the soil to a pH below 4. In an acidic bactericidal environment, rotting bacteria die, and plant remains settle to the bottom and are compressed, turning into peat.

The meaning of mosses. Bryophytes in nature often settle on such substrates and in such habitats that are inaccessible to other plants. In this case, they act as pioneer vegetation, playing an important role in soil-forming processes. Bryophytes play a significant role in the regulation of the water balance of the land. They regulate the evaporation of moisture from the soil.

In the meadows, mosses prevent the seed renewal of grasses, in the forests - the germination of tree seeds. By accumulating water, mosses cause waterlogging of the soil. Sphagnum and green mosses are the main peat formers. The presence of moss cover is one of the main stabilizing factors in permafrost conditions.

Economic value. Animals do not eat moss. Peat is used as fuel, bedding for pets, fertilizer. By dry distillation of peat, methyl alcohol, saccharin, wax, paraffin, paints, etc. are obtained. Peat is used to make paper and cardboard. In construction, peat is used as a heat-insulating and sound-insulating material. Sphagnum also has medical significance - it is used as an excellent dressing material.

Key terms and concepts

1. Kukushkin flax. 2. Gaustoria. 3. Equospores of bryophytes. 4. Protonema. 5. Dioeciousness of cuckoo flax. 6. Sphagnum. 7. Assimilation and aquifer cells of sphagnum. 8. Pioneer vegetation.

Essential Review Questions