Selaginella, commonly known as spikemoss or club moss, is the only living genus of the family Selaginellaceae and contains more than 800 species. It is a pteridophyte and is distributed all around the world, with the highest diversity found in tropical regions.

Seedless vascular plants are often found in shady areas, but certain species can also be found in seasonal dry or xerophytic conditions. These plants can be seen on tree trunks, rocks, forest floors, and other surfaces.

Table of Contents

Classification

Morphology

Anatomy

Reproduction and Life Cycle

[Frequently Asked Questions](#Frequently Asked Questions)

#Classification

| Kingdom | Plantae |

| Subkingdom | Tracheobionta |

| Division | Lycopodiophyta |

| Class | Lycopodiopsida |

| Family | Selaginellaceae |

| Genus | Selaginella |

Some of the common species of Selaginella include:

S. kraussiana (golden clubmoss)

S. erythropus (ruby-red spikemoss)

S. lepidophylla (resurrection plant)

S. uncinata (peacock moss)

Structure

The main plant body is a sporophyte. It is a vascular plant and is differentiated into root, stem and leaves. Some of the important features are:

• Vascular tissue for transporting water and nutrients
• Root system for anchoring and absorbing
• Stem for support and photosynthesis
• Leaves for photosynthesis

Morphology

It is an evergreen, abundantly branched and fragile herb.

Primary roots are short-lived, whereas adventitious roots are present at the tips of rhizophores.

Rhizophores are leafless, colourless branches that develop from the prostrate stem and grow downwards. When it reaches the soil, adventitious roots develop at the tip of the rhizophores.

The stem of the plant is green, dichotomously branched, and can be either erect or prostrate with erect branches.

A single apical cell is typically located at the apex of a growing stem.

Leaves are small with pointed tips and have a scaly texture.

Leaves contain an unbranched midrib.

The subgenus Homophyllum has leaves that are arranged in a spiral pattern, and all the leaves are of the same type.

The subgenus heterophyllum consists of two types of leaves; small leaves located on the dorsal side of the stem, and larger leaves located on the ventral side of the stem, occurring in pairs.

Sporophylls, or spore-bearing leaves, are structurally similar to ordinary leaves, but are found in clusters known as strobilli. These sporophylls are typically located at the tips of branches and contain sporangia.

Ligules are small outgrowths present on the abaxial side of the leaf at the base.

Anatomy

Stems

The epidermis is composed of a cuticle which surrounds a layer that is hairless and lacks stomata.

The epidermis is followed by a well-defined cortex region. This region is either parenchymatous, or is differentiated into an outer sclerenchymatous region and an inner parenchymatous region.

The number of steles in different species varies, but in general, they are protostelic, with xylem surrounded by phloem cells.

Stele is surrounded by a single-layered pericycle, and pith is typically absent.

Xylem lacks companion cells and phloem lacks vessels.

Root

The epidermis is the outermost covering of a plant and is surrounded by a thin layer of cuticle. Root hairs arise from the epidermis.

The cortex is composed of either solely parenchymatous cells or both sclerenchymatous hypodermis and parenchymatous inner cortex.

The endodermis may or may not be clearly delineated.

The Pericycle is composed of parenchyma and can have one to three layers.

Stele is a Protostele, with Exarch (Protoxylem present at the periphery) and Monarch Xylem.

Rhizophore

The structure of rhizophore is similar to that of roots. However, the epidermis of rhizophore does not contain stomata or hairs.

Stele is a protostelic. Xylem is either exarch or mesarch.

Leaf

The epidermis is a single-layered tissue, and stomata are predominantly found in the lower epidermis.

Epidermis cells do not have chloroplasts.

The mesophyll is the layer located between the upper and lower epidermis, and is composed of parenchyma cells. The amount of chloroplasts in the mesophyll differs between species.

In some species, the mesophyll cells can differentiate into upper palisade and lower spongy tissues.

A single median vascular bundle is present, containing xylem tracheids surrounded by sieve elements of phloem, which is then surrounded by a single layered bundle sheath.

Reproduction and Life Cycle

Selaginella exhibits both vegetative and sexual reproduction. Vegetative reproduction takes place through tubers, buds and fragmentation, while sexual reproduction occurs through spore formation.

Vegetative Reproduction

Adventitious branches can give rise to new plants.

At the end of the growing season, vegetative reproduction through tubers can occur. When conditions are favorable, tubers will form at the apex of aerial branches and will give rise to a new plant.

The resting buds located at the tip of some aerial branches are able to withstand unfavorable conditions and form rhizophores in favorable conditions.

Sexual Reproduction

Selaginella is heterosporous, producing two types of spores: microspores, which give rise to male gametophytes, and megaspores, which give rise to female gametophytes.

Sporophyte

Microspores develop in microsporangia and megaspores develop in megasporangia. They are borne on microsporophylls and megasporophylls, respectively. The aggregation of microsporophyll and megasporophyll forms a structure called strobilus.

In some species, the strobilus is monosporangiate, with either a microsporophyll or a megasporophyll, whereas in most cases it is bisporangiate.

Each microspore mother cell divides by meiosis to produce microspore tetrads. These microspore tetrads are formed from cells of sporogenous tissue present inside the microsporangia, and each microspore is haploid.

The megaspore mother cells that form within the megasporangia will undergo meiosis, with the exception of one which will disintegrate. This single functional megaspore mother cell will then divide into four haploid megaspores. In certain species, only one megaspore is produced.

Male Gametophyte

Microspores germinate into male gametophytes within the microsporangia. On maturity, the microsporangium dehisces, releasing the spores which are then carried away by the wind. The spores are typically liberated when they have developed to the 13-cell stage, which consists of one prothallial cell, four androgonial cells, and eight jacket cells. The primary androgonial cells then divide and develop into antherozoids, which are biflagellate and swim towards the archegonium.

Female Gametophyte

Megaspores germinate into female gametophytes that develop inside the megasporangium. After fertilisation or formation of the archegonium, the female gametophyte is liberated and attaches to a suitable substratum. Rhizoids are then formed that help with anchoring and absorption of water.

The gametophytic tissue contains the archegonium.

Anterozoids swim and reach towards the archegonium. Water is essential for fertilisation. The nucleus of antherozoids and egg fuses to give rise to a diploid zygote or oospore after fertilisation. The oospore is the initial sporophytic generation. The oospore divides and forms a multicellular structure that differentiates into various tissues such as stem, root, cotyledons, rhizophore, etc.

In some species, oospore development is completed in the megasporangium, and a seedling with primary roots is formed before it falls to the ground.

Life Cycle

Selaginella, like other pteridophytes, shows an alternation of generations. The life cycle alternates between a diploid sporophyte generation and a haploid gametophyte generation. This type of life cycle is referred to as a haplo-diplontic life cycle.

The diploid sporophyte is the dominant phase in the life cycle and is the main plant body. It is differentiated into true roots, stem, and leaves.

Selaginella is heterosporous, producing two types of spores: microspores and megaspores. These spores are haploid and are produced by meiosis in the spore mother cells. Upon germination, the spores develop into male and female gametophytes. These gametophytes are small but are free-living, multicellular, and photosynthetic.

The fusion of male and female gametes from antheridia and archegonia, respectively, results in the formation of a diploid zygote that develops into a well-differentiated sporophyte.

Frequently Asked Questions

What are the uses of Selaginella?

Selaginella is used in food, medicine, ornaments and handicrafts.

Selaginella’s Common Name

Selaginella’s common name is ‘clubmoss’.

Selaginella, also known as starry spike moss, is a genus of plants.

The plant known as Sanjivani is an Indian medicinal herb, commonly known as Indian Ginseng or Winter Cherry.

Selaginella bryopteris is the plant known as ‘Sanjivani Booti’ which was mentioned in the Hindu epic, ‘Ramayana’.