Features of Structure and Reproduction of Higher Spore Plants

Bryophytes

Representatives of the Bryophyte division are found on all continents, but they are more common in areas with temperate and cold climates. Mosses grow on
soil, bogs, in coniferous forests, and can grow on tree bark, stones, and sand, often displacing lichens. There are mosses that live in water bodies.

In lower-organized mosses, the body is a thallus, while in more highly organized ones, it has a leafy-stem structure. They attach to the substrate with rhizoids.
In the life cycle of mosses, two phases alternate: sporophyte and gametophyte. The gametophyte dominates.

The gametophyte looks like a shoot, divided into stems and leaves; rhizoids perform the function of roots. The sexual organs are multicellular antheridia (where
male gametes - spermatozoids - are formed) and archegonia (where female gametes - egg cells - are formed).

The sporophyte (sporogonium) consists of a cylindrical stalk, at the top of which is a capsule. A sporangium with spores forms in the capsule.

The body of leafy mosses is always divided into a stem and leaves. Liverworts, unlike leafy mosses, have a thallus or leafy-stem structure. The stem has a radial
 structure, and the leaves are arranged spirally. Rhizoids are multicellular. Antheridia and archegonia are grouped at the top of the stem or on lateral branches.
The sporogonium consists of a haustorium, a stalk, and a capsule with a lid.

Representatives of the order Green Mosses are mainly found in bogs and some types of forests. They are characterized by diverse structures. The sexual
reproduction organs are located on the main axes (acrocarpous mosses) and on the lateral branches (pleurocarpous mosses). The gametophyte is often dicotyledonous.

A typical representative of acrocarpous green mosses is the common haircap moss. Its stem is straight, unbranched, densely covered with sessile,
linear-lanceolate leaves with a pointed tip, up to 30 cm high. It attaches to the soil with multicellular rhizoids.

The stem is covered with an epidermis, followed by a layer of mechanical tissue consisting of elongated cells with thickened walls, then the cortex and
parenchyma containing starch. In the center of the stem is a conducting bundle of xylem surrounded by phloem.

The sporogonium has a complex structure. In the center of the capsule is a column that transitions into an epiphragm at the top, covering the capsule. Sporangia
of a bag-like shape are attached to the column and the walls of the capsule, and the capsule is covered by a calyptra. The sporogonium has an adaptation for
spore dispersal - a peristome. These are hygroscopic teeth located around the edge of the capsule. In dry weather, they open outward, facilitating spore dispersal,
and in wet weather, they bend inward, pressing the epiphragm against the capsule, preventing water from entering.

Before spore formation, reduction division occurs. Under favorable conditions, the spore germinates into a protonema, from which a dicotyledonous gametophyte grows.

Antheridia at the top of male specimens are elongated and surrounded by apical yellow or reddish leaves. They produce biflagellate spermatozoids. Archegonia
are grouped at the top of female plants, alternating with sterile threads (paraphyses) and also surrounded by apical leaves. Thus, the gametophyte of the haircap
moss is an independently existing green plant, while the sporophyte always develops on the gametophyte and can only partially synthesize organic substances independently.

The order Sphagnales, or White Mosses, includes one genus, Sphagnum, which comprises 350 species that grow in boggy forests, bogs, occupying large areas
in northern Europe, Asia, North America, and also in temperate regions of the southern hemisphere. They are called white because they have a whitish color
when dry.

The gametophyte of Sphagnum consists of a branched stem and leaves. In adult plants, rhizoids are absent. Growth is apical. The anatomical structure of the
stem and leaves of Sphagnum is unusual. In the center of the stem are living thin-walled parenchymatic cells that perform the role of conducting tissue. Behind
these cells are several layers of narrow prosenchymatic cells with thickened brownish walls, and on the outside is a multilayered epidermis consisting of large
dead cells. These cells have pores and are filled with water. The leaf of Sphagnum has no vein, consisting of a single layer of cells of different shapes and sizes.
Some cells are living, elongated, chlorophyll-bearing, while others are dead, larger, and can accumulate a large amount of water, 30-40 times the mass of the moss itself.

Mosses are pioneers in colonizing open and disturbed habitats, playing an important role in soil formation. A continuous moss cover in the forest retains moisture
and has water-conservation significance.

Ferns

The division Pteridophyta is a large and extremely diverse group of spore plants. They are distributed worldwide. The dominant generation is the diploid sporophyte.

The male fern has a shortened stem represented by a rhizome, at the top of which is a cluster of leaves. These leaves are modified shoots and, unlike the leaves
of angiosperms, grow not from the base but from the tip. On the underside of the leaf are sori - groups of sporangia covered by kidney-shaped indusia. When the
 spores mature, the sporangia open. From the dispersed meiospores, haploid bisexual gametophytes germinate. The gametophyte is green. The fertilization process
is inseparably linked with water. During fertilization, a diploid zygote is formed, giving rise to a new sporophyte. Initially, the development and nutrition of the
sporophyte occur at the expense of the assimilating gametophyte.

The mass extinction of tree-like ferns in the Carboniferous period led to the formation of coal deposits, which are valuable fossil resources.