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Systematic Position

Division: Lycopodiophyta

Class: Isoetopsida

Order: Selaginellales

Family: Selaginellaceae

Genus: Selaginella

Habit and Habitat

Selaginella, with about 700 species, is cosmopolitan in

distribution (Banks, 2009). The species are commonly

known as spike moss or small club moss. Most of the

species inhabit damp and shaded forests of tropics,

but some (e.g., S. densa, S. rupestris, S. lepidophylla)

grow in xerophytic habitats, such as exposed rock

surfaces. S. oregano is an epiphyte that

Fig 1: Habit of Selaginella growing in xerophytic

conditions

grows on tree trunks in tropical rain forests. Several

species of Selaginella are grown in gardens as

ornamentals (Rashid, 1999). Some xerophytic species

of Selaginella (e.g., S. lepidophylla, S. pilifefra) show

caespitose habit; they curl and become ball like during

dry season and again become green and fresh when

moisture is available. These are called resurrection

plants (Singh et al, 2000).

Fig 2: Selaginella showing caespitose habit

Selaginella is particularly interesting from

comparative evolutionary perspective because it has

retained the independent but water-dependent

gametophytic generation that is typical of all non-seed

plants. Because its gametophyte is not buried within

maternal tissues of the sporophyte, Selaginella is also

a useful experiment system for investigating how the

alternation of generations (the switch between haploid

gametophyte and diploid sporophyte) is regulated

(Banks, 2009)

The genus is represented in India by more than

70 species. Among these species, Selaginella

kraussiana, S. monospora, S. biformes, S. rupestris,

S. megaphylla, S. bryopteris, S. ciliaris, S.

chrysorhizos and S. pentagona are common.

Morphology

The sporophytic plant body of Selaginella is

differentiated into root, stem and leaves. Besides

some species also have rhizophores.

1. Roots. The primary roots are ephemeral and the

adult plant has adventitious roots. The adventitious

roots usually have specific locations in relation to stem

dichotomies. In most of the creeping species with

dorsiventral stems (e.g., S. kraussiana, S. laevigata),

roots arise at or close to the point of dichotomy; in

species like S. rupestris and S. wallichii they arise at

the point of dichotomy as well as at other positions;

and in S. selaginoides and S. spinulosa they arise

from knot-like swellings present at the basal portion

of the stem.

The roots arise endogenously and are

dichotomously branched. The dichotomies are at right

angles to each other. The main function of root is to

anchor the plant in the soil and absorb water and

mineral salts from the soil. Besides it form a passage

way for water and dissolved substances from the root

into the stem and also for foods from the stem down

into the root.

Fig 3: Adventitious roots in Selaginella

2. Rhizophore. In some species of Selaginella,

many long, cylindrical, unbranched and leafless

structures arise from the lower side of the stem at the

point of dichotomy. These grow vertically downward

and bear tuft of adventitious roots at their distal end.

They are known as rhizophores (Goebel 1905; Bower,

1935). The rhizophore may develop into a typical leafy

shoot under certain conditions. Like a typical root it

grows downwards to the soil and absorbs water

through its tissues in a direction reverse of that in

which it has grown. It produces lateral endogenous

roots and helps in anchoring the plant to the

substratum.

Fig 4: Showing various organs like rhizophore,

cone and leaves in Selaginella

3. Stem. The stem is erect and dichotomously

branched in the sub-genus Homoeophyllum, and

prostrate or sub-erect with lateral branching in the

sub-genus Heterophyllum.

The stem apex usually has a single well-defined apical

cell, but in S. oregano a group of meristematic cells

has been observed.

4. Leaves. The leaves of Selaginella are

microphyllus, sessile and simple. Their shape varies

from ovate to lanceolate. The leaf has a single

midvein that remains unbranched throughout its

course. Most of the species have thin and soft leaves,

but in xerophytic species they are thick. The

vegetative leaf as well as sporophyll, has a small

membranous projection on its adaxial (upper) surface,

close to the base. The projection is known as the

ligule. The basal part of the ligule has a distinct

hemispherical foot-like structure, called glossopodium.

It is composed of highly vacuolated thin-walled

tubular cells. The ligule is embedded at the base of

the leaf in a pit like structure, known as ligular pit.

The projected part of the ligule is only one cell in

thickness and is tongue-like (e.g., S. svogelli, S.

martensii). It develops precociously and matures long

before its associated leaf. Although the definite

function of ligule is not known, it has been suggested

that in some way they are associated with water

absorption and secretion, and thus prevent

desiccation of the shoot. Some consider that the

ligules in Selaginella are concerned with upward

movement of inorganic solutes, and thus compensate

for smaller and less effective leaf primordia.

In the sub-genus Homoeophyllum, all leaves are

alike and spirally arranged. But the species belonging

to the sub-genus Heterophyllum, have two types of

leaves- two dorsal rows of small leaves (microphylls),

and two ventral rows of large leaves (megaphylls).

The leaves occur in pairs and the two leaves of a pair

are always unequal.

Anatomy

1. Root.

A cross section of a root shows a simple structure.

The epidermis is made up of tangentially elongated

cells. In exposed roots, the outer wall of epidermal

cells is cutinized, but in roots that penetrate the

substratum, the epidermal cells are delicate and have

root hairs.

The cortex is usually homogenous, consisting of many

layers of thin parenchymatous cells. But in some

species the outer layers of the cortex become thick-

walled and form hypodermis. In S. selaginoides, the

parenchymatous cells of the cortex show mycorrhizal

association. The innermost layer of the cortex forms

endodermis. In species like S. densa and S. rubella

endodermis is fairly distinct.

The central part of the root is occupied by a

protostele, surrounded by 1-3 layers of

parenchymatous pericycle. The xylem, which forms

the central solid core of the stele, is monarch to

tetrarch and exarch. The phloem occurs in the form of

a ring around the xylem.

2. Rhizophore.

The anatomy of the rhizophore resembles that of the

root. Some variations in the internal organization are

due to the fact that the rhizophore is an aerial

structure, whereas the root is a subterranean organ.

The epidermis is single layered and the outer wall of

the epidermal cells is covered with a thick layer of

cuticle. Root hairs, characteristic of roots, are absent

on rhizophores. The cortex is differentiated into an

outer sclerenchymatous and an inner relatively wide

parenchymatous zone. The innermost layer of the

cortex forms endodermis. The protostele of the

rhizophore is surrounded by a parenchymatous

pericycle. Usually the stele is monarch and exarch, but

shows some variations. For example, in S. atro-viridis,

the metaxylem is crescent-shaped with many

protoxylem strands on its concave side, and in S.

kraussiana the xylem is centrifugal.

Fig 5: Cross section of rhizophore

3. Stem.

Internally, the stem is more complex than the root.

The anatomy of the stem shows variations not only in

different species, but also within the same species

depending on stem diameter. A transverse section of

the stem shows epidermis, cortex and central

cylinder.

Fig 6: Internal structure of Selaginella stem

The epidermis is the outermost unistratose layer. The

outer walls of the epidermal cells are highly cutinized.

The epidermis is devoid of stomata and hairs.

The cortex is usually composed of compactly arranged

parenchymatous cells without intercellular spaces. But

in mature stems of many species outer layers of

cortex become partially sclerenchymatous, forming a

tough hypodermis. In xerophytic species (e.g., S.

rupestris, S. lepidophylla), most part of the cortex is

composed of thick-walled cells.

A distinctive feature of Selaginella stem is the

presence of radially elongated endodermal cells, called

trabeculae. They have characteristic casparian bands

on their lateral walls. Due to the presence of

trabeculae, the central stele is separated from the

cortex by large air spaces. In fact, in a transverse

section the stele appears suspended in an axial air

column with the help of trabeculae. The air spaces

develop due to more rapid expansion of the cortical

region than the stele. This differential growth also

results in radial stretching of some endodermal cells.

Xerophytic species of Selaginella, however, do not

have trabeculae.

Fig 7: Showing trabeculae in Selaginella stem

The number of steles in the stem shows considerable

variation in different species of Selaginella. For

example, the stem is monostelic in S. spinulosa and S.

flabellata, distelic in S. kraussiana, and polystelic

(with 12-16 steles) in S. laevigata. Besides, the

number of steles may also vary within different parts

of the same plant. For example, the creeping

branches of S. braunii are distelic, whereas the erect

branches are monostelic; and in S. lyalli, the creeping

branches are distelic and the erect branches are

polystelic.

The stele is surrounded by a single-layered pericycle.

The shape and structure of the stele is also variable. It

is circular in S. kraussiana and flat or ribbon-like in S.

viridangula and S. vagelii. Most of the species have a

protostele with a solid xylem core surrounded by

phloem, but S. laevigata var. lyalii has a siphonostele.

The xylem is usually monarch (S. kraussiana), or

diarch (S. selaginoides). It usually consists of only

tracheids; the protoxylem tracheids have annular or

helical thickenings; whereas the metaxylem tracheids

show scalariform thickenings. In S. oregana, S. densa

and S. rupestris, however, the xylem has true vessels

with transverse perforation plates. Although

secondary growth is absent, some secondary xylem

elements have been found in the basal part of the

stem of S. selaginoides.

4 Leaf.

Both, the upper and the lower epidermis of the leaf

are unistratose. The epidermal cells have chloroplasts.

The leaves are mostly amphistomatic, but sometimes

they are hypostomatic, as in S. martensii. Stomata

are distributed mostly in the midrib region.

The mesophyll consists of loosely arranged thin-

walled cells, with many small or large intercellular

spaces. It is usually made up of only spongy

parenchyma, but occasionally a distinct palisade layer

may be present towards the morphological upper side.

A mesophyll cell has 1-8 cup shaped chloroplasts,

which have many spindle shaped pyrenoid-like bodies.

The leaf has a median vascular bundle surrounded

by a distinct bundle sheath. The xylem, which

occupies the central part of the bundle, consists of

only tracheids with annular or spiral thickenings. It is

surrounded by phloem.

Reproduction

The sporophyte of Selaginella reproduces

vegetatively and by spores.

Vegetative reproduction

Vegetative propagation in Selaginella takes place

by tubers, bulbils, dormant buds and by

fragmentation.

In S. rupestris, prostrate branches produce roots

during favorable conditions. These root bearing

prostrate branches separate from the parent plant and

grow into new sporophytes.

Species like S. chrysorhizos and S. chrysocaulos

propagate with the help of tubers and bulbils. The

tubers may be aerial, developing at the apices of

aerial branches (e.g., S. chrysocaulos) or

subterranean (e.g., S. chrysorhizos). During favorable

conditions the tuber germinates into a new

sporophyte. Aerial branches of S. chrysocaulos also

bear some dormant (resting) buds which grow into

new plants during favorable conditions.

Fig 8: Tubers in Selaginella

Reproduction by spores

Selaginella is a heterosporous pteridophyte; it

produces two types of spores –megaspores and

microspores. The megaspores form female

gametophytes on germination and the microspores

give rise to male gametophytes. The sporangia are

strictly dimorphic, i.e., micro and megaspores are

formed in separate sporangia. The sporangia bearing

microspores are called microsporangia, and those

bearing megaspores as megasporangia. There are

many microspores in a microsporangium, while each

megasporangium usually has 1-4 (or rarely more)

megaspores. The megaspores are much larger than

the microspores.

The sporangia are borne singly in the axils of

sporophylls. The sporophyll-bearing micro-sporangium

is called microsporophyll, and the one with

megasporangium is known as megasporophyll. The

sporophylls are spirally arranged around a central axis

to form a strobilus.

Fig 9: Parts of strobilus showing megaspores and

microspores in Selaginella

Strobilus or cone. In most of the species of

Selaginella, sporophylls are aggregated at the apex of

the main stem and its branches in definite loose or

compact cones, called strobili (singular = strobilus).

The size of the strobilus varies from 5mm to 6-7 cm.

It is often inconspicuous due to its small size, and

similarity between sporophylls and vegetative leaves.

Usually a branch terminates in strobilus, but in species

like S. cuspidata and S. patula, vegetative growth of

the branch may continue beyond the strobilus. In S.

erythropus, a second strobilus is produced on the

fertile branch after an intervening vegetative region.

Thus, in this species sporophylls and vegetative leaves

occur in alternate segments.

Distribution of micro and megasporangia in

strobilus. In most of the species of Selaginella, both

micro and megasporangia are found within the same

strobilus. Their distribution is specific. For example, in

S. selaginoides, S. rupestris and S. helvetica,

megasporangia are present in the basal part and

microsporangia in the upper part of the strobilus; in S.

kraussiana there is only a single megasporangium at

the base of the strobilus, and the rest are

microsporangia; and in S. inaequalifolia one side of

the strobilus bears only megasporangia, and the other

microsporangia. In S. martensii and S. caulescens,

mega-and microsporangia do not show any definite

arrangement. In S. selaginoides, a series of basal

sporangia are non- functional. The two types of spores

are never present within the same sporangium.

In S. gracilis and S. atroviridis, strobili are

monosporangiate, i.e. micro and megasporangia

are borne in separate strobili.

Development of sporangium. The initial stages of

the development of micro and megasporangium are

similar. Both develop from the transverse row of initial

cells, i.e. the development is of eusporangiate type.

The sporangial initials divide periclinally, establishing

outer jacket initials and inner archesporial initials. The

archesporial initials undergo repeated anticlinal and

periclinal divisions forming a mass of sporogenous

cells. Simultaneous divisions also occur in the jacket

initials and the derivatives eventually form a two-

layered sporangial jacket. The cells of the outermost

layer of the sporogenous tissue (adjacent to the inner

wall layer) form a nutritive layer, known as tapetum.

The tapetal layer disintegrates as spores mature.

The last generation of sporongenous cells functions

as spore mother cells. The micro and

megasporangium differ in subsequent development.

Further development of microsporangium. In

microsporangium about 80-90% spore mother cells

are functional, and behave as microspore mother

cells. The remaining spore mother cells degenerate

and form a viscous nourishing fluid. The functional

spore mother cells undergo meiosis and form haploid

microspores, which are arranged in tetrahedral

tetrads.

Further development of megasporangium. In

megasporangium, all spore mother cells but one,

degenerate. The functional spore mother cell behaves

as megaspore mother cell. It divides meiotically

forming four tetrahedrally arranged haploid

megaspores. All the four megaspores derived from a

megaspore mother cell may not always be functional.

For example, in S. sulcata only one, and in S.

rupestris two megaspores are functional. Sometimes

there are more than one megaspore mother cells in a

megasporangium and in such cases the

megasporangium has 8 or more megaspores. The

megaspores are much larger than microspores.

The expression of maleness or femaleness is not

genetically determined; it appears to be influenced by

the nutritional factor, and the specific environment in

which the sporangium develops.

Mature sporangium. Mature sporangia are

stalked structures, with a two-layered sporangial

jacket. The cells of outer jacket layer are elongated

and contain chloroplasts. The micro and mega

sporangia differ in shape, size and colour. The

microsporangia are slightly elongated, yellow, red or

orange in colour. The megasporangia are larger and

paler and assume the shape dictated by the enlarging

megaspores within.

The mature sporangium dehisces along the line of

dehiscence present at its distal end and oriented

transverse to the axis of the sporophyll. Structural

modification of the surface cells along this line and at

its flanks results in splitting of the distal part of the

sporangium into two valves. The lower cup-shaped

part of the sporangium shrinks on drying and throws

out spores violently.

Gametophyte

The spore is the mother cell of the gametophytic

generation. As mentioned earlier, Selaginella is

heterosporous and produces two types of spores- the

smaller microspore and the larger megaspores. This

difference in the size of the spores is related to their

fate and function; microspores develop into male

gametophyte and megaspores into female

gametophytes.

In Selaginella both microspores and megaspores

begin to germinate while still inside the sporangium

(i.e., they germinate in situ). Thus, spores are shed at

multicellular stage.

Microspores and development of male

gametophyte

Microspores: The microspores are small,

spherical structures, ranging 0.015-0.06 mm in

diameter. A microspore is surrounded by a thick

ornamented exine and a relatively thin intine. The

ornamentations in the exine may be papillate,

echinulate or granulate. The spore has a single

haploid nucleus and granular cytoplasm, rich in fatty

substances. The fats probably provide food to the

developing male gametophytes as spores contain no

chlorophyll.

Development of male gametophyte: The

microspores germinate inside the microsporangium

and are shed at 13- celled stage. The first division of

the microspore is asymmetrical and as a result a small

lenticular prothallial cell and a large antheridial initial

is established. The prothallial cell does not divide

further and the entire sporangium develops from the

antheridial initial.

The first division of the antheridial initial is nearly

at right angles to the prothallial cell. It results in the

formation of two antheridial cells of almost equal size.

Both these cells divide by a vertical wall to produce a

group of four cells. Thus, at this stage the

gametophyte consists of five cells (four cells derived

from the antheridial initial and a prothallial cell). The

two basal cells, derived from the antheridial initial, do

not divide further, whereas the upper two daughter

cells divide repeatedly and form ten cells. At this

stage the gametophyte has 13 cells (10 cells derived

from the upper daughter cells of the antheridial

initial,2 basal daughter cells and 1 prothallial cell).Of

these, four central cells function as primary

androgonial cells and eight peripheral ones as jacket

cells. The male gametophyte is shed from the

microsporangium at 13-celled stage. It enters into

partially opened megasporangium where further

development of the male gametophyte takes place in

close proximity of the developing female

gametophyte. In some species, it is believed, that

further developed of the male gametophyte takes

place in the soil.

The four central primary androgonial cells of the

male gametophyte divide repeatedly forming a mass

of 128-256 antherozoid mother cells or androcytes.

Each androcyte metamorphoses into a spindle-shaped

biflagellate antherozoid. The antherozoids of

Selaginella are perhaps the smallest amongst the

vascular plant.

With the formation of antherozoids, the jacket

cells decompose and form a mucilaginous substance.

The antherozoids float in this substance. Until this

stage the male gametophyte is completely enclosed

within the wall of the microspore. Thus it is entirely

endosporic and extremely reduced structure. Unlike

other pteridophytes, vegetative prothalli are not

formed in Selaginella. The gametophyte is not set free

and is dependent on the parent sporophyte for

nutrition.

Megaspore and development of female

gametophyte

Megaspores: Megaspores are much larger than

the microspores. Their diameter varies from 0.15 to

0.5 mm. Usually all megaspores in a megasporangium

are approximately of the same size, but in S.

molliceps one megaspore is larger than the other

three, and in S. stenophylla there are two large and

two small megaspores. The megaspores are also

arranged in tetrahedral tetrads. The wall of the

megaspore is differentiated into an outer massive

exine and an inner thin intine, but in S. rupestris and

S. apus it is differentiated into three distinct layers-

the outer exospore, the middle mesospore and the

inner endospore. The megaspore has a single haploid

nucleus, surrounded by granular cytoplasm, rich in

fatty substance.

Development of female gametophyte: Like

male gametophyte, the development of the female

gametophyte of Selaginella also begins while it is still

within the megasporangium. In S. kraussiana, the

gametophyte is liberated from the megasporangium

after the first archegonium is differentiated, whereas

in S. rupestris and S. apus it is retained in the

megasporangium even after the development of

embryo has started. However, in S. spinulosa and S.

helvitica the development of female gametophyte

starts only after the megaspore is shed from the

sporangium.

Immediately after the development of female

gametophyte initiates, a large vacuole appears in the

centre of the megaspore and as a result the cytoplasm

is pushed along the spore wall in the form of thin

membrane. There is considerable enlargement of the

megaspore. The outer spore wall (exospores) grows

more rapidly than the mesospore and endospore,

consequently a large gap is formed in between the

exospore and mesospore. At this stage, the exospore

is attached to the mesospore only at one point. The

space between the exospore and the mesospore is

filled with a homogenous liquid.

The haploid nucleus of the megaspore divides

repeatedly without any wall formation. The free nuclei

are unequally distributed in the peripheral cytoplasm;

they are clustered beneath the triradiate ridge of the

spore and sparsely distributed elsewhere. Now, wall

formation begins in the apical region and a lens-

shaped pad of small cells is formed at the apical end.

It is separated from the rest of the female

gametophyte by a distinct diaphragm. The

cytoplasmic layer becomes thicker gradually and

pushes the mesospore outward. As a result the

mesospore again comes in contact with the exospores.

With the increase in the amount of cytoplasm, the

central vacuole diminishes and eventually disappears.

The part of the gametophyte below the diaphragm is

multinucleate in early stages but becomes

multicellular as wall formation proceeds inward. At

this stage, the spore wall ruptures along the triradiate

ridge exposing the apical cellular pad. The exposed

part of the female gametophyte may develop

chloroplasts but the photosynthetic ability of this part

is of limited importance as food for the developing

embryo is stored in the lower multicellular part of the

gametophyte. Many rhizoids develop from the

exposed part of the gametophyte. They attach the

gametophyte to the substratum and also help in

absorption of water.

Development of archegonia: Archegonia

develop from the apical tissue of the gametophyte. All

superficial cells of this tissue have the potential of

forming archegonia. The archegonial initial divides

periclinally into a primary cover cell and a central cell.

The primary cover cell divides by two vertical divisions

at right angles to each other and forms four neck

initials. The neck initials divide transversely so as to

form eight neck cells, arranged in two tiers of four

each, in the meantime, the central cell divides by a

periclinal wall and an outer primary neck cell and an

inner primary venter cell is established. The former

does not divide further and directly functions as neck

canal cell, whereas the latter divides transversely into

a venter canal cell and an egg.

The mature archegonium of Selaginella has two cell

long neck (consisting of eight cells in two tiers of four

each), a neck canal cell, a venter canal cell and an

egg. The four terminal cells of the neck project

beyond the surface of the gametophyte as asymmetric

nipples. Rest of the archegonium remains embedded

in the tissue of the gametophyte

Fig 10: Spores and their fate

Fertilization

Fertilization usually takes place after the

megasporangium has fallen on the soil, but in some

species it may occur while the female gametophyte is

still within the sporangium. Just before fertilization,

the neck cells of the archegonium separate from each

other and form a passage for the entry of

antherozoids. After liberation from the male

gametophyte, antherozoids swim in rain or dew water

and reach the archegonia. Usually only one

antherozoid enters into an archegonium and fuses

with the egg to form a diploid zygote.

Some species of Selaginella (e.g., S. rupestris, S.

apoda) show seed habit. In these species, the

sporangium has only a single megaspore and at

maturity of the archegonium the spore wall ruptures,

but the developing female gametophyte does not

come out of the spore wall. The developing male

gametophyte, when shed from the microsporangium

(present in the distal part of the strobilus) lands on

the partially open megasporangium. Thus, at this

stage, both the male and the female gametophytes lie

within the megasporangium. As such fertilization and

embryo development take place inside the

megasporangium. The sporangium is shed after the

development of root and primary shoot of the new

sporophyte. This feature is of considerable importance

from the point of view of seed habit because when the

megaspore with young sporophyte is shed, it has all

typical characters of a seed.

Development of embryo

The diploid zygote is the mother cell of the

sporophytic generation. It divides transversely,

establishing an epibasal (upper) suspensor cell and a

hypobasal (lower) embryonic cell. As development

proceeds, the suspensor cell repeatedly divides to

form a suspensor, which pushes the developing

embryo deep into the female gametophyte. The rest

of the embryo develops from the embryonic cell. It

divides by two vertical walls at right angles to each

other, and thus a four-celled embryo is formed. One

of the four cells of the embryo divides by an oblique

vertical wall, and thus an apical cell with three cutting

faces is established. This eventually functions as the

apical cell of the embryonic shoot.The remaining three

cells of the 4-celled embryo and the sister cell of the

apical cell (i.e., total four cells) divide transversely to

form two tiers of four cells each. The cells of both the

tiers divide irregularly forming a multicellular embryo.

Usually the cells of lower tier divide more rapidly than

the upper tier and due to this differential growth the

entire embryo apex rotates at 1800 and emerges

through the apical part of the gametophyte. The

derivatives of the lower tier form the foot. At first the

foot grows on one side but eventually comes to lie

opposite the suspensor. The foot acts as a haustorial

organ; its main function is to absorb nutrition for the

developing sporophyte from the female gametophyte.

At this stage, a superficial cell in each of the two

diagonally opposed quadrants of the upper tier

differentiates as the apical cell of a foliar appendage,

which eventually forms a cotyledon. In the axil of each

cotyledon a ligule develops.

The part of the embryo immediately posterior to

cotyledons develops into hypocotyledonary part of

the stem. The stem grows with the help of the apical

cell of the embryo. After the formation of cotyledons

and stem, the apical cell of the root differentiates on

the lateral surface of the foot. The derivatives of this

cell develop into a root-like structure, called

rhizophore. Roots, in fact, develop at the apex of the

rhizophore. In early stages of development the young

sporophyte is attached to the megaspore and derives

its food from the female gametophyte with the help of

its foot. But after the establishment of root and stem,

the sporophyte becomes independent.

Fig 11: General life-cycle of Selaginella

Medicinal uses

Many species of Selaginella have been used as

traditional medicines. In India, S. bryopteris is

referred to as Sanjeevani—one that infuses life—for its

medicinal properties (Sah et al. 2005). In Columbia,

S. articulata is used to treat snakebites and neutralize

Bothrops atrox venom. Throughout southern China,

Selaginella is used as a popular herb for the treatment

of various ailments (Lin and Kan, 1990; Pan et al

2001 and Maa et al 2003). Although most reports of

the medicinal uses of Selaginella are anecdotal,

researchers have begun to identify and characterize

the active compounds in Selaginella extracts (Kang et

al. 2004; Chen et al. 2005 and Yin et al. 2005).

Among the best characterized are uncinoside A and

uncinoside B, biflavonoids that have potent antiviral

activities against respiratory syncytial virus (Ma et al

2003). Other biflavonoids from S. tamariscina inhibit

the induction of nitric oxide (NO) and prostaglandins

(Pokharel et al 2006; Woo et al 2006; Yang et al,

2006), which are involved in the pathogenesis of

some cancers (Lala and Chakraborty, 2001; Zha et al

2004). The biflavone ginkgetin from S. moellendorffii

selectively inhibits the growth of some cancer cells by

inducing apoptosis (Sun et al 1997; Su et al 2000).