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Riccia

Bryophytes are non-vascular plants that include mosses, liverworts, and hornworts. Riccia is a genus of thallose liverworts commonly found growing terrestrially or aquatically. It has a flat, lobed gametophyte thallus with dichotomous branching and a midrib furrow containing its sexual organs. Riccia reproduces both vegetatively through thallus fragmentation and sexually through the fertilization of archegonia by antheridia-derived sperm. This results in a sporophyte embedded in the gametophyte that produces haploid spores through meiosis. The spores germinate to form new gametophyte plants,

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Riccia Bryophytes
What are bryophytes Bryophytes are a group of plants that include mosses, liverworts and hornworts. They are the non-vascular plants.
Riccia taxonomic classification Division Bryophyta Class Hepaticopsida Order Marchantiales Family Ricciaceae Genus Riccia
Habitat and examples Majority of the members of this genus are terrestrial but some species are aquatic, and they are forund growing in water. The following seven species have been commonly reported in Riccia robusta; R. melanospora; R, cruciata; R. sanguinea,’ R. himalayansis; R.pathankotensis, Riccia robusta; R sanguinea and R. pathankotensis These species are found in Punjab plains , river beds, bank of river and canals, and along the streams
Species found in punjab
Vegetative structure ( notch, furrow, lobes)  It is a thalose liverwort.  The plant body is gametophyte and generally it appears as rosette because of extensive growth of thallus lobes. ( it shows repeated dichotomy)  The thallus grows flat on the ground and each lobe has a notch at the apex , which has at the growing point .  Lobes are thicker in middle and thinner from margins  A deep cleft or furrow is present at the mid of each lobe.  The sex organs are embedded in this furrow  In some aquatic species like R. fluitans have narrow ribbon like furrow having repeated dichotomous branches .
Rhizoids  Rhizoids are also present on the ventral surface of the thallus  The rhizoids are present on the middle and are of two types 1. Smooth and tuberculate e.g Marchantia
scales  the scales are also present on the ventral side 1. In older parts they are arranged in 2 rows 2. While in younger parts they are arranged in 1 row.
Internal structure of thallus  It is made up of parenchymatous cells , that are bound of upper and lower epidermis  There are 2 regions 1. Upper assimilatory region (photosynthetic region) 2. Lower storage region
Upper assimilatory region  It is made vertical rows of cells  They are 6 to 8 cells in height and contain large air spaces  They are rich in chloroplast and form photosynthetic tissue  In the upper epidermis the spaces work as air pores for exchange of gases  Uppermost cells of these vertical rows of chlorophyll-containing cells remain devoid of chloroplast and thus form a hyaline discontinuous layer of upper epidermis.  Continuity of the upper epidermis is broken by many air pores.
Lower storage region 1. Lower storage region ( compact parenchyma cells contain few chloroplast, mostly colorless) but rich in starch . 2. Sometime also store water 3. They are without intercellular spaces 4. They have closely packed parenchyma cells 5. these lower storage region cells from scales and rhizoids
Transverse section of thallus
REPRODUCTION  multiply vegetatively by the decay or death of the Older parts which results in the separation of younger branches, each of which grows into an independent plant  In certain species (R. fluitans) small adventitious lateral branches may be produced from the ventral side of the thallus, these adventitious branches on detachment give rise to new plants,  Formation of vegetative reproductive gemma-like multicellular bodies at the apices of rhizoids have also been reported in certain species.
SEXUAL REPRODUCTION  Riccia plants may be monoecious or dioecious depending upon the species  Both the male (antheridia) and female (archegonia) reproductive organs are produced in acropetalous ( equal) order on the dorsal side of the thallus in the median furrow.  In the monoecious species the antheridia are generally produced earlier than the archegonia.
Antheridium: Antheridium is present in a cavity on the dorsal surface called antheridial chamber. 2. Antheridial chamber has a narrow opening or pore on the apical side. 3. A mature antheridium is a stalked, club-shaped or pear-shaped body. 4. Antheridial stalk is multicellular. 5. It remains surrounded by an outermost layer of one- celled thick sterile jacket. 6. Inside the jacket layer are present many small, cubical androcyte mother cells. 7. Each androcyte mother cell contains dense cytoplasm and large nucleus. It divides diagonally into two androcytes. 8. Each androcyte metamorphoses into a single structure, variously called antherozoid, spermatozoid or sperm. 9. Each antherozoid is a minute, uninucleate body containing two long flagella at its anterior end. 10. Lower flagellum is slightly larger than upper one. 11. Dehiscence of antheridium takes place in the presence of water.
Archegonium:  The archegonium remains embedded in the archegonial cavity on the dorsal surface of the gametophyte.  Upper part of the neck of archegonium generally protrudes out of the cavity.  An archegonium is a flask-shaped structure made up of a long, elongated neck and a globular venter.  Venter is sessile and surrounded by a one-celled thick layer, made up of 12 to 20 cells.  Neck consists of 4 to 6 neck canal cells, and remains surrounded by six vertical rows of cells.  Each longitudinal row consists of 6 to 9 cells.  At the tip of the neck are present four cover cells or lid cells.  Venter contains an upper, small ventral canal cell and a lower, large egg cell.  At the time of fertilization all the cells, except the egg, disintegrate and form a mucilaginous liquid, which gives entry to the spermatozoids. The ultimate product of the fertilization is zygote.  The ultimate product of the fertilization is zygote.
Archegonia
Sporogonium:  It is simple and made up of only capsule or spore-sac  Foot and seta are absent.  It remains embedded in the gametophyte, and it is a non-green structure, thus depending entirely on the gametophyte for food.  Inside sporogonium are present many spore mother cells which remain surrounded by a capsule wall and two-layered calyptra.
 Spore mother cells divide reductionally, and each of them thus forms four haploid spores, arranged tetrahedrally.  6. Prior to the formation of spores, the wall of the sporogonium as well as the inner layer of calyptra dissolve, and thus only a single-layered calyptra is present outside the spores.  7. Elaters are absent .  8. Neck of the long archegonium may remain outside for some time but it ultimately withers.
Spore  It is the first cell of the gametophytic generation.  Shape of the spore is rounded or pyramidal.  Each spore is surrounded by a thick, black or sculp- tured wall.  Wall of the spore consists of three layers: outermost exine or exosporium, which is thick and sculptured; middle thin mesosporium and: innermost, thin intine or endosporium  Spores are unicellular and uninucleate structures.  In the cytoplasm are present many oil globules.  Spores germinate into gametophyte.
Germination of spore
Life cycle