Riccia is a bryophyte under the order Marchantiales. It has a small thalloid plant body which is not differentiated into root stem and leaves and the plant body is a gametophyte

1. RICCIA
BY DR. MARIA THERESA
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2. SYSTEMATIC
POSITION
Genus : Riccia
Division :
Bryophyta
Family : Ricciaceae
Order : Marchantiales
Class :
Hepaticopsida
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3. General Characteristics
• Most widely distributed genus of the family
Ricciaceae consisting of 200 species of which 35
are from India
• Named in the honour of P F Ricci.
• Most of the species are terrestrial, which grows
in damp places but, Riccia fluitans is an aquatic
species.
• Examples of a few Indian species are; R.
gangetica, R. discolor, R. himalayensis, R.
glauca, R. crystallina, R. frostii, R. hirsuta, R.
melanospora. , R. kashyapii and R. pandei.
• Plant body shows alternate generation.
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4. Gametophytic Generation
• The plant body of Riccia is gametophytic.
• Thallus is small, flat, dorsiventral, fleshy, prostrate and dichotomously
branched. Dichotomy leads to the rosette like appearance.
• Dorsal surface
 Light green in colour.
 Thick midrib.
 Median longitudinal groove ending in a depression call apical notch.
 Growing point situated in apical notch.
• Ventral surface
 The ventral surface of thallus bears many scales and rhizoids.
 Scales are multicellular and one celled thick structures.
 Scales are arranged along the margin in a single row.
 Rhizoids are unicellular and un-branched.
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Dorsal groove Apical notch

5. Anatomy of
Gametophytic thallus
• The green photosynthetic region made up of unbranched photosynthetic
filaments separated by narrow air chambers.
• All the cells of the photosynthetic filament except the uppermost one are
isodiametric and possess many chloroplasts.
• Terminal cells are large, hyaline and makes a discontinuous epidermis.
Upper
Photosynthetic
Zone
• This zone lies below the photosynthetic zone.
• It consists of compactly arrangedparenchymatouscells devoid of chloroplast
• Contain starch as reserved food material. The lowermost cell layer of this
zone forms the lower epidermis.
• Some cells extend to form the scales and both types of rhizoids.
Lower Storage
Zone
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6. Scales and Rhizoids
• Rhizoids are of two types:
o Tuberculate – the inner wall layer
modifies into peg-like in growth
which projects into the cell lumen. It
helps in anchorage.
o Smooth walled – both inner and
outer walls are smooth. It helps in
absorption.
• Scales:
o Present on ventral side.
o Two types – simple and ligulate.
o Helps to protect growing point.
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7. Reproduction
1. Vegetative Reproduction
 Fragmentation
 Death and decay of older portions
 Formation of adventitious branches.
 Persistent growing apices.
 Formation of tubers.
 By rhizoids.
2. Sexual reproduction
 Sexual reproduction in Riccia is oogamous.
 Male reproductive bodies are known as antheridia and female as archegonia.
 Some species of Riccia like R. crystallina, R. gangetica, etc. are monoecious or homothallic while other
species like R. frostii, R. discolor, etc. are dioecious or heterothallic.
 Antheridia and archegonia remain enclosed with in the antheridial and archegonial chambers and develop on
the dorsal surface of the thallus.
 Sex organs develop in acropetal succession.
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8. Antheri
dium
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Antheridum
Basal stalk Oval body
• Short
• Stalk attaches the
antheridium to the
base of the antheridial
chamber.
• It has a flat base with
conical apex.
• A single-layered
sterile jacket encloses
the mass of
androcytes which
metamorphoses into
antherozoids.
• Antheridium is present singly in an antheridial chamber.

9. Spermatog
enesis
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1Androcyte
mother cell
2
triangularand
rocyte
Ovalandroc
yte
Blepharoplast
elongates
Crescent
shaped
nucleus
2 flagella
fromblephar
oplast
Matureanther
ozoid
• A mature antherozoid is unicellular, uninucleate, biflagellate and coiled
structure.
• Both flagella resemble morphologically but differ in function i.e., one
for propulsion and other for rotation.

10. Dehiscence of Antheridium
• Antheridium dehisce in the presence of water.
• Water enters the antheridial chamber and the sterile apical cells of the
antheridial jacket enlarge by absorbing water and ultimately breaks
open.
• The cell walls form the semifluid content.
• The mature antherozoids along with semifluid mass, come out of the
antheridium to the antheridial chamber and then to the dorsal surface
of the thallus.
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11. Archegonium
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Archegonium
Stalk Neck Venter
• Short
• Helps to
remain
attached to
the thallus.
• Elongated, slender
neck.
• Six vertical rows of
cell enclose 4 – 6
neck canal cells.
• Single layered
ventral wall.
• Single, small
ventral canal
cell.
• Single, large
egg.

12. Fertilization
• The antherozoids released after dehiscence swim on the dorsal surface of the
thallus and reach the mouth of the archegonium.
• The ventral canal cell and neck canal cell disintegrates forming a mucilaginous
mass which absorbs water, swells up and opens the cover cell apart.
• Many antherozoids enter the archegonial neck.
• One of the antherozoid fertilize the egg. Male and female gamete nuclei fuse to
form a diploid zygote.
• This marks the end of gametophytic phase.
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13. Sporophytic Generation
• The mature Sporophyte has a globular capsule embedded within the dorsal
surface of the gametophytic thallus.
• Foot and seta are completely absent.
• The capsule has a single layered capsule jacket and is also covered by a bilayered
calyptra.
• Before sporogenesis, the capsule wall and inner layer of calyptra disintegrates.
• Spores are the first cell of the gametophytic generation. Each spore has 3 wall
layers, namely exosporium, mesosporium & endosporium. They are liberated
after the complete death and decay of the older gametophyte.
• Spores are liberated by wind or rain.
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14. 14
Gametophyte with
Sporogonium
Spores
Calyptra

15. Germination of Spores
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16. 16
Life
Cycle

17. Thank
You
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