External & Internal Morphology of Equisetum

1. External Morphology of
Equisetum
Dr. Vasanta I. Kahalkar
Department of Botany
M. G. Arts, Science & Late N. P.
Commerce College, Armori

2. External Morphology of Equisetum
• Division – Sphenophyta
• Class – Sphenopsida
• Order – Equisitales
• Family – Equisitaceae
• Genus – Equisetum
• The sporophyte, i.e., the plant body is well
differentiated into – stem, leaves and roots.

3. The stem: Stem is underground,
horizontal and much branched,
which often penetrates more than a
meter into the soil. The rhoizome is
jointed and provided with nodes and
internodes. It gives off two types of
branches – sterile and fertile branches.
Sterile branches are green in colour,
persistent and have a whorl of lateral
branches at each node. Sterile branches
are vegetative in function. Fertile
branches are generally unbranched,
short lived and bears a single strobilus
at its tip.

4. A whorls of lateral branches is present at each node
of the vegetative shoot.These branches are of the
following two types.
1. Branches of Unlimited growth- They are further branches
like the main vegetative shoot and are differentiated into
nodes and internodes.
2. Branches of limited growth- They are also differentiated
into nodes and internodes like vegetative shoot but
remain unbranched.
• Leaves – Leaves are small, slender, scale-like. They are
arranged in whorls at each node. They are fused at the
base and free at the tip which forms a teeth like structure.
They form a cup like structure at the base of the
internodes.
• Roots - Roots are slender, much branched and adventitious
(fibrous type). They occur only at the nodes of the
rhizomes.

5. T.S. of Root:
• The root in transverse section shows – epidermis,
cortex and stele.
1. Outermost layer is epidermis, from which arise many
root hairs.
2. Cortex is thick and multi-layeredand differentiated into
an outer sclernchymatous and an iiner paranchymatous
region.
3. Outer zone of cortex consists of 3 to 4-celled thick
exodermis.
4. Inner zone is parenchymatous with many intercellular
spaces.
5. Endodermis is two-layered. He cells of the outer
endodermal layer are larger and have casparian bands
but those of the inner endodermal layer are smaller and
without casparian bands.
6. Pericycle is absent.
7. Stele is a protostele, which is diarch or tetrarch. A large
metaxylem tracheid is present in the centre of the stele
and protoxylem strands lie around it.
8. Phloem is present in between the protoxylem strands.

6. Internal Structure of Stem Equisetum

7. • It is wavy in outline because of the presence of ridges and grooves.
• Outermost layer is the epidermis, cells of which have a deposit of
silica in their outer and lateral walls.
• Due to the presence of silica, the stem appears hard and rough to
touch.
• The continuity of epidermis is broken by sunken stomata present in
each groove. In each sunken stoma, the guard cells are covered
completely by subsidiary cells, thus giving the appearance of two sets
of guard cells.
• Below the epidermis is present a-well-developed cortex.
• Just below each ridge is present a large patch of sclerenchyma, which
is mechanical in function. Sclerenchyma is also present below the
grooves in between chlorenchyma.
• Inner to be sclerenchyma is present chloren-chymatous tissue below
each ridge. It is photosynthetic in function.
• Rest of the cortex is parenchymatous and many layered.
• Just below each groove is present a large air canal in the
parenchymatous cortex. It is known as vallecular canal.
• Innermost layer of cortex is the endodermis, the cells of which
contains casparian strips.

8. • Below the endodermis is present a single-layered pericycle.
• Vascular bundles are present below the ridges, i.e., alternate to the
vallecular canals of the cortex. They are present in the ring.
• The number of vascular bundles and vallecular canals is equal to
the number of ridges and grooves, respectively.
• Stele is of ectophloic siphonostelic type.
• Each vascular bundle is conjoint, collateral, closed, and consists
of xylem, phloem and some parenchyma.
• In each Vascular bundle is present a water- containing cavity or
canal called carinal canal.
• Xylem is ‘V’- shaped.
• Protoxylem is endarch lying opposite to carinal cavity. It consists
of annular and spiral tracheids.
• Two strands of metaxylem are present.
• Phloem is present in between two strands of metaxylem and made
up of phloem parenchyma and sieve tubes.
• Pith is present in the form of pith cavity, located in the centre of
the aerial shoot.

9. THANKU YOU