LYCOPODIUM (CLUB MOSS)

CLASSIFICATION OF LYCOPODIUM (CLUB MOSS)

Kingdom :-  Plantae

Division :- Pteridophyta

Sub-division :- Lycopsida

Class :-  Lycopodiopsida

Order :- Lycopodiales

Family :- Lycopodiaceae

Genus :- Lycopodium

EXTERNAL FEATURES OF LYCOPODIUM (CLUB MOSS)​

• The plant body consists of creeping rhizome which gives off slender, elongated aerial branches from the upper side and adventitious roots from the lower. The aerial branches vary from 3-8 inches in length. L. cernum is exceptional in attaining a height of 2 feet or more.
• Habitat. Most of the species are terrestrial and the sporophyte may either have an upright stem or a horizontally creeping stem. Some species grow as epiphytes on higher plants which show pendent habit e.g. L. phlegmaria, L. squarrosum.
• The branchingis mostly dichotomous but in some species it may be monopodial also.
• The stemand its branches are densely covered with small leaves present in close spirals or whorls.
• The leavesare entire, small and membranous, rarely, exceeding 1 cm in length. Each leaf is supplied by a single mid-vein which runs almost unbranched right upto the apex.
• Epidermis :-The walls of the epidermal cells of the leaf are sinuous.
• Stomata :-Stomata are more or less parallel to the midrib. These are equally distributed on both of the leaf surfaces.

ANATOMY OF ROOT OF LYCOPODIUM (CLUB MOSS)​

• The root is differentiated into an epidermis, cortex and the stele.
• Theepidermis is single layered and gives rise to root hairs, the latter occur in pairs.
• The cortexis several layered and in older roots a few of the outer layers become sclerified. The inner cells are thin walled and parenchymatous without any intercellular spaces.
• The steleranges from monarch to tetrarch but generally it is diarch with two protoxylem masses.
• The xylem is C or U shaped and is so oriented that the opening of C or U faces away from the stem.
• The protoxylem is present at the tips of C or U and the intervening portion consists of metaxylem.
• The phloem is present in between the arms of C or U.

ANATOMY OF STEM OF LYCOPODIUM (CLUB MOSS)​

• A transverse section of the stem shows an epidermis, a wide cortex and a stele.
• Epidermisis single layered and is provided with stomata.
• The stemhas certain ridges and grooves. Chloroenchyma is present in the ridges.
• Cortex :The structure varies from species to species. In some species, it is parenchymatous throughout, in others the inner and other portions are thick walled, and in still others the entire cortex is thick walled.
• Endodermis :-It is single layered and lies inner to cortex. In older stems, however, the endodermis may not be well defined.
• Pericycle:- The endodermis is follows this layer which is composed of 3 to 6 cells.
• Stele :-The centre is occupied by a protostele. Three different types of styles are found in species of Lycopodium.
  1. In some species viz. L. clavatum and L. complanatum, it is definitely organised into a plectostele i.e. xylem and phloem occur in alternating bands that are more or less parallel.
  2. In other species viz. L. seratum and L. phlegmaria, it is star-shaped with 4 arms in which grooves are occupied by phloem. This is known as actinostele.
  3. In still other species, as exemplified by L. cernum, it is a haplostele in which the xylem strands lie scattered in phloem.
• The xylemis exarch with protoxylem facing towards the periphery and metaxylem towards the centre.
• The tracheidsin metaxylem are scalariform while in protoxylem they are spiral or annular.
• The phloemconsists of unicellular sieve tubes, with numerous sieve plates, and phloem parenchyma. The companion cells are absent.
• Leaf tracesare seen to traverse the cortex.

ANATOMY OF LEAF OF LYCOPODIUM (CLUB MOSS)​

• The epidermis is single layered. The stomata are equally distributed on both the sides.
• The leaf has a single vascular strand which is concentric with xylem in the centre.
• The cells between the epidermis and the vascular strand form spongy parenchyma.

SPORE PRODUCING ORGAN :- SPORANGIA

• External features of strobilus. Sporangia are the spore producing organs. These are grouped to form strobili which are situated at the apices of branches. (In L. selago distinct strobilus is lacking and the vegetative and reproductive regions alternate each other).
• s. of the strobilus shows a central strobilar axis with spirally arranged sporophylls.
• Each sporophyll bears a sporangium near its base on the adaxial side.
• A sporangium is a black, kidney shaped structure, with a long or short massive stalk.
• Sporangium consists of a wall and the cavity with spore.
• The wall of sporangium is several layered thick. Tapetum forms the innermost layer.
• The cavity has many spores, arranged in tetrahedral tetrads. Since all the spores are of one type, the plant is called homosporous.
• Each spore is a minute structure with a triradiate ridge. It has a thick and spiny exine and a thin and membranous intine.
• The spores germinate to form the prothallus.

GAMETOPHYTE OF LYCOPODIUM (CLUB MOSS)​

• The gametophytes may be subterranean or subaerial.
• The sub-aerial type is green, about 2 or 3 mm in length and bears the sex organs.
• The subterranean type is non-green and is bigger as compared to the sub-aerial type. It generally consists of a tuberous body with a lobed crown that bears the sex organs.
• The prothallus is monoecious and the sex organs lie almost wholly embedded in the tissue of the prothallus except the uppermost portion.
• The antheridium is spherical with a single layer of jacket, containing within, a number’ of antherozoids or antherozoid mother cells. The antherozoids are fusiform and biciliate.
• The archegonium is a narrow elongated structure. It has a narrow venter with an egg and venter canal cell and a long neck generally containing 4-6 neck canal cells.

IDENTIFICATION

• DIVISION – Pteridophyta
  1. True roots generally present (except in Psilopsida),
  2. True vascular strand present.
• Sub-division:- Lycopsida
  1. Laves microphyllous.
  2. Sporangia borne singly on adaxial face of the sporophyll or in its axil.
  3. Sporophylls borne in strobili.
• Order– Lycopodiales
  1. Stem has protostele.
  2. Sporophytes homosporous.
• Family – Lycopodiaceae
  1. Leaves without ligules.
  2. Sporophylls and foliage leaves may be similar or dissimilar in shape.
• Genus – Lycopodium
  1. The sporophyte is long and always more than 2 inches.
  2. Sporangia kidney-shaped.
  3. Stele either a plectostele or actinostele or haplostele.

REFERENCES

• https://www.shutterstock.com/search/LYCOPODIUM+(CLUB+MOSS)
• https://en.wikipedia.org/wiki/Lycopodium