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Here is a list of thirty-seven thallophytes:- 1. Gloeocapsa 2. Oscillatoria 3. Lyngbya 4. Nostoc 5. ANABAENA 6. Scytonema 7. Stegonema 8. Gloeotrichia 9. Rivularia 10. Westiellopsis 11. Nostocopsis 12. Pininularia 13. Biddulphia 14. Euglena 15. Chlamydomonas 16. Volvox 17. Ulothrix 18. Cladophora 19. Draparnaldia 20. Fristchiella 21. Coleochaete 22. Trentepohlia 23. Oedogonium 24. Zygnema and a few others.
1. Gloeocapsa:
Thallus Structure:
Thallus is unicellular and colonial. Colonies are jelly, like coloured yellowish to brownish. Cells are spherical to ovoid and are surrounded by well-defined, thick, stratified envelopes (sheaths) and thus forming colonial appearance. Each cell contains granular cytoplasm without any demarcation of organelles and nuclei (Fig 2.1).
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Reproduction is by Fission:
Identification:
Thallus blue green in colour, cells devoid of conspicuous nucleus, absence of any sex organ, absence of cell organelles like plastids, presence of gelatinous sheath around the cell.
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CLASS: CYANOPHYCEAE
Plant body unicellular, colonial.
ORDER: CIIROOCOCCALES
Cells spherical to ovoid in shape surrounded by mucilage sheath.
FAMILY: CHROOCOCCACEAE
Cell envelop or sheath thick and stratified, mostly coloured; colonies jelly-like and adhere to the surface of rocks or soil.
GENUS: GLOEOCAPSA
2. Oscillatoria:
Thallus Structure:
Thallus is blue-green in colour. Trichomes are un-branched, cylindrical and devoid of sheath. Extremity of trichome is distinctly being straight or curved or coiled and apical cell somewhat rounded (convex) or variously shaped. Cells are 2 – 3 times broader than longer. The cell protoplasm is granular with many vacuoles. Nuclear body is not visible under ordinary resolution. Fresh living trichome exhibits oscillating movement. Plant is mucilaginous.
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Reproductive Structure:
Hormogonia:
They are formed by the death of a cell or group of cells here and there in the trichome. There is presence of conspicuous separation disc between two adjoining vegetative cells in order to delimit the hormogonia. Separation discs are double concave and hyaline (Fig 2.2).
Identification:
Thallus blue-green in colour, cells devoid of conspicuous nucleus, absence of any sex organ, presence of gelatinous sheath around the cells, (in most cases), absence of organised cell organelles like plastids.
CLASS: CYANOPHYCEAE
Thallus un-branched, filamentous, presence of hormogonia, heterocyst present in some genera only.
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ORDER: NOSTOCALES
Un-branched trichome devoid of heterocyst’s, trichome devoid of sheath, or with very fine, almost inperceptible sheath.
FAMILY: OSCILLATORIACEAE
Trichome un-branched, cylindrical cells 2-3 time wider than longer, cytoplasm granular with vacuoles, sheath absent or extremely thin. Fresh plants exhibit oscillating movement.
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GENUS: OSCILLATORIA
N. B. Lyngbya differs from Oscillaloria in having a prominent gelatinous sheath surrounding the trichome. In Phormidium several trichomes are embedded within a common sheath formed by the gelatinization of individual sheaths of trichomes.
3. Lyngbya:
Thallus Structure:
Thallus is filamentous. Filaments are inter woven to form an expanded thallus mass. Each filament has a distinct sheath (thin to thick). There is a single trichome in each sheath, which is straight and un-constricted. Sheath is extended beyond the trichome in the apical zone.
Cells are 2 – 3 times wider than longer. Cells contain granular and vacuolated cytoplasm (Fig. 2.3).
Reproductive Structure:
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Hormogonium:
It is formed by the dissolution of the intercalary cells of the trichome and is a few cells in length.
Identification:
Thallus blue-green in colour, cells devoid of conspicuous nucleus, absence of any sex organ, presence of gelatinous sheath around the cells, (in most cases) absence of organised cell organelles like plastids.
CLASS: CYANOPHYCEAE
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Thallus un-branched, filamentous, presence of hormogonium, heterocyst present in some genera only.
ORDER: NOSTOCALES
Un-branched trichome devoid of heterocyst’s, trichome devoid of sheath, or with very fine, almost inperceptible sheath.
FAMILY: OSCILLATORIACEAE
Presence of conspicuous sheath around each trichome, sheath mostly extended above the apical regions of the growing trichomes.
GENUS: LYNGBYA
4. Nostoc:
Thallus Structure:
Plant body is blue-green in colour, free floating colonial or attached to a substratum. Each colony contains a number of trichomes embedded within a matrix (common sheath) forming little balls-Nostoc balls. The trichomes consist of a single series of uniform, often Toulouse, bead-like, ellipsoidal cells more or less depressed which are often contorted and sometimes form densely interwoven masses.
Cells of each trichome are joined end to end to form moniliform (bead-like) chains. Sheaths of individual trichomes are thin, mucilaginous and diffluent. Intercalary heterocyst’s are present. Heterocyst’s are distinguished from the vegetative cells by thick-walls, transparent contents, larger size and two polar nodules at two ends. Heterocyst’s separate the hormogonium (Fig. 2.4).
Reproductive Structure:
Akinetes:
They are different in appearance from vegetative cells. Akinetes are spherical or oblong and much larger than vegetative cells with dense protoplasm.
Identification:
Thallus blue-green in colour, cells devoid of conspicuous nucleus, absence of any sex organ, presence of gelatinous sheath around the cells, (in most cases) absence of organised cell organelles like plastids.
CLASS: CYANOPHYCEAE
Thallus un-branched, filamentous, presence of hormogonium, heterocyst present in some genera only.
ORDER: NOSTOCALES
Trichomes un-branched, interwoven and surrounded by sheath, presence of heterocyst’s and akinetes.
FAMILY: NOSTOCACEAE
Trichomes with single series of uniform ellipsoidal (bead-like) cells, presence of intercalary heterocyst’s and akinetes.
GENUS: NOSTOC
5. ANABAENA:
Thallus Structure:
Plant body is blue-green in colour, free floating. Colony is not firm, i.e., does not form any definite shape. Trichomes are composed of single row of cells. They are not contorted. Sheath is absent or diffluent. Several trichomes may occur within a soft, mucilaginous sheath. Heterocyst’s are intercalary and slightly larger than vegetative cells, transparent, thick-walled and with two polar nodules (Fig. 2.5).
Reproductive Structure:
Akinetes:
These are differentiated from vegetative cells and are thick-walled, elongated, with densely accumulated stored materials and intercalary in position.
Identification:
Thallus blue-green in colour; cells devoid of conspicuous nucleus, absence of any sex organ, presence of gelatinous sheath around the cells, (in most cases) absence of organised cell organelles like plastids.
CLASS: CYANOPHYCEAE
Thallus un-branched, filamentous, presence of hormogonium, heterocyst present in some genera only.
ORDER: NOSTOCALES
Trichomes un-branched, interwoven and surrounded by sheath, heterocyst’s and akinetes present.
FAMILY: NOSTOCACEAE
Trichomes solitary or colonial, colonies do not form definite shape, solitary trichomes often within a more or less diffluent sheath, or sheath absent, akinetes elongated.
GENUS: ANABAENA
6. Scytonema:
Thallus Structure:
Plant body is un-branched, filamentous. The filaments are interwoven into a felt mass. Filaments are embedded within sheaths which may be hyaline or coloured and have prominent diverging strata. Each filament shows distinct basal and apical regions. The filaments often show false branching which originate laterally. Intercalary heterocyst’s are present. Cells contain granular cytoplasm, vacuoles and are devoid of organised nuclei (Fig 2.6).
Reproductive Structure:
Hormogonium:
It is a few cells in length and is usually separated by heterocyst’s. Heterocyst’s are hyaline cells with two polar nodules. Akinetes are rarely found.
Identification:
Thallus blue-green in colour, cells devoid of conspicuous nucleus, absence of any sex organ, presence of gelatinous sheath around the cells, (in most cases) absence of organised cell organelles like plastids.
CLASS: CYANOPHYCEAE
Thallus un-branched, filamentous, presence of hormogonium, heterocyst present in some genera only.
ORDER: NOSTOCALES
Plant body filamentous, filaments uniseriate, un-tapered, un-branched, trichome bears conspicuous sheath and characteristic false branching.
FAMILY: SCYTONEMATACEAE
Filaments interwoven into a felty mass, presence of intercalary heterocyst’s and characteristic false branching, sheath prominent, hormogonium present.
GENUS: SCYTONEMA
7. Stegonema:
Thallus Structure:
Plant body is branched, filamentous. Branching is irregular and variously curved. Filament in older region is composed of 2 to many rows of cells. Sheath around each trichome is thicker in older trichomes (Fig 2.7).
Reproductive Structure:
Heterocyst:
It is intercalary or lateral in position. It is roundish in shape.
Hormogonium:
It is formed at the end of young branches, two to few cells in length.
Identification:
Thallus blue-green in colour, cells devoid of conspicuous nucleus, absence of any sex organ, presence of gelatinous sheath around the cells, (in most cases) absence of organised cell organelles like plastids.
CLASS: CYANOPHYCEAE
Filament showing true branching, trichomes composed of several rows of cells, mostly with heterocyst’s, hormogonium present.
ORDER: STIGONEMATALES
Filament branched irregularly and curved at places, sheath around trichome distinct.
FAMILY: STIGONEMATACEAE
Filaments of older region multi-axial – 2 to many rows of cells in each trichome, heterocyst roundish, intercalary or lateral in position; hormogonium formed at the tip of young branches.
GENUS: STIGONEMA
8. Gloeotrichia:
Thallus Structure:
Thallus is colonial. Colony appears as spherical to hemispherical and gelatinous. Each colony is exceedingly firm in consistency and contains numerous radiating filaments with repeated false branching in which, each branch terminates into a multicellular colourless hair.
One or two heterocyst’s are located at the broad basal end of the trichome. The lower and broader portion of the filament is covered by a sheath. Cells contain granular, undifferentiated and vacuolated cytoplasm (Fig 2.8).
Reproductive Structure:
Hormogonium:
It is formed from the upper part of the trichome. It is composed of a few cells.
Akinete:
It is an elongated and thick-walled body. It is situated just above the rounded basal heterocyst.
Identification:
Thallus blue-green in colour, cells devoid of conspicuous nucleus, absence of any sex organ, presence of gelatinous sheath around the cells, (in most cases) absence of organised cell organelles like plastids.
CLASS: CYANOPHYCEAE
Thallus un-branched, filamentous, presence of hormogonium, heterocyst present in some genera only.
ORDER: NOSTOCALES
Trichomes un-branched, heterocyst basal in position, terminal part colourless, hair-like.
FAMILY: RIVULARIACEAE
Trichome differentiated into base and apex, partly covered by sheath. Heterocyst basal and roundish, akinetes long, cylindrical and thick walled; akinetes situated just above the heterocyst, filaments showing false branching.
GENUS: GLOEOTRICHIA
9. Rivularia:
Thallus Structure:
Thallus is un-branched, filamentous, but showing false branching. Filaments are colonised in more or less radial or parallel order in hemispherical or spherical mucilaginous colony. Trichomes mostly ending in a hair. Filaments often show trichothallic growth and are completely included within the gelatinous sheath. Filament contains a meristematic zone in intercalary position. It is composed of several cells (Fig 2.9).
Reproductive Structure:
Heterocyst:
It is basal or intercalary in position.
Hormogonium:
It is formed singly or in a group, particularly towards the base of the meristematic zone.
Akinete:
Absent
Identification:
Thallus blue-green in colour, cells devoid of conspicuous nucleus, absence of any sex organ, presence of gelatinous sheath around the cells, (in most cases) absence of organised cell organelles like plastids.
CLASS: CYANOPHYCEAE
Thallus un-branched, filamentous, presence of hormogonium, heterocyst present in some general only.
ORDER: NOSTOCALES
Thallus un-branched, filamentous and forming a hemispherical or spherical mucilaginous colony; trichome often ending in a hair-like structure.
FAMILY: RIVULARICEAE
Filament within a gelatinous sheath, Heterocyst basal, often with false branching at the base.
GENUS: RIVULARIA
10. Westiellopsis:
Thallus Structure:
Thallus is branched, filamentous. Filaments are of two kinds – primary filament which is slightly thicker and more or less creeping and secondary filament which is generally thinner and grows erect. Filaments are devoid of gelatinous sheath and consist of a single row of cells. Cells of the filament are short and barrel-shaped.
Reproductive Structure:
Heterocyst:
It is formed on secondary filament at intercalary position. It is cylindrical to roundish in shape (Fig 2.10).
Identification:
Thallus blue-green in colour, cells devoid of conspicuous nucleus, absence of any sex organ, presence of gelatinous sheath around the cells, (in most cases) absence of organised cell organelles like plastids.
CLASS: CYANOPHYCEAE
Filament showing true branching, mostly with heterocyst’s.
ORDER: STIGONEMATALES
Filament branched irregularly and curved at places.
FAMILY: STIGONEMATACEAE
Filaments loosely entangled, lateral branches clearly seen, cells of main filament short, barrel-shaped, cylindrical; heterocyst’s intercalary and cylindrical.
GENUS: WESTIELLOPSIS
11. Nostocopsis:
Thallus Structure:
Thallus is sparsely branched, filamentous. Trichomes are embedded in a soft diffluent sheath. There are two types of trichomes – one type consists of a long, many-celled structure while the other type is short and few celled (i.e., with limited growth).
Reproductive Structure:
Heterocyst:
It is formed on lateral branches and is 2 – 3 cells in length. It is intercalary or terminal or even basal in position. It is also broader than vegetative cells.
Hormogonium:
It is often formed terminally (Fig 2.11).
Identification:
Thallus blue-green in colour, cells devoid of conspicuous nucleus, absence of any sex organ, presence of gelatinous sheath around the cells, (in most cases) absence of organised cell organelles like plastids.
CLASS: CYANOPHYCEAE
Thallus un-branched, filamentous, presence of hormogonium, heterocyst present in some genera only.
ORDER: NOSTOCALES
Un-branched trichome devoid of heterocyst’s, trichome devoid of sheath or with very fine, almost imperceptible sheath. Trichome un-branched, heterocyst basal in position, terminal part colourless, hair-like.
FAMILY: NOSTOCHOPSIDACEAE
Trichomes sparsely branched, cells longer than broad, heterocyst’s on 2 – 3 celled lateral branches, spherical, conical, heterocyst’s intercalary also, intercalary heterocyst’s broader than vegetative cells.
GENUS: NOSTOCOPSIS
12. Pinnularia:
Thallus Structure:
Thallus is unicellular and cells are bilaterally symmetrical, pinnate or valve type. When one of the valves is visible it is known as valve view. Each cell has two halves, both halves are alike, but the outer one (epitheca) is slightly larger than the inner one (hypotheca) and elliptical to lanceolate in shape. Each valve has a straight raphe with distinct central and polar nodules visible in girdle view.
The symmetrical frustules have valves that are inflated in the middle or somewhat straight parallel sides and with rounded poles. The striations are smooth, parallel and transverse. Within each cell two laminate chromatophores with pyrenoids are conspicuous. The cell wall is very rigid, highly silicified and beautifully ornamented (Fig. 2.12).
Identification:
Thallus unicellular, cell wall highly silicified. Each cell has two overlapping frustules and conspicuous chromatophores, and oil droplets as stored food.
CLASS: BACILLARIOPHYCEAE
Cells bilaterally symmetrical, pinnate or valve type, cells with raphe, wall ornamentation bilateral with respect to a line.
ORDER: PENNALES
Cell frustule with true raphe, cells with two laminate chromatophores.
SUB ORDER: NAVICULINEAE
Valves symmetrical on both axes, valves elliptical to lanceolate.
FAMILY: NAVICULACEAE
Valves with smooth transverse costae, raphe straight.
GENUS: PINNULARIA
13. Biddulphia:
Thallus Structure:
Thallus is unicellular and cells are transversely compressed and have valves that bear cylindrical, conical or globular processes at their angles. The walls of the cells are highly silicified and coarsely, areolate. There is usually an intercalary band between the girdles.
The girdles and intercalary bands are conspicuously ornamented. Cells contain conspicuous discoid chromatophores. Each cell is composed of two distinct halves (frustules) and each half is radially symmetrical and somewhat circular in outline (Fig 2.13).
Identification:
Thallus unicellular, cell wall highly silicified and composed of two overlapping halves, cells contain distinct chromatophores and oil droplets as stored food.
CLASS: BACILLARIOPHYCEAE:
Cell covering circular and radially symmetrical.
ORDER: CENTRALES
Cell radially symmetrical and having conspicuous horn-like processes, intercalary band present in-between the girdles.
SUB ORDER: BIDD ULPIIINEAE
Cells centric with horn-like processes, cells with many chromatophores.
FAMILY: BIDDULPHIACEAE
Cells transversely compressed with characteristic processes at angles, chromatophores – a few in each cell.
GENUS: BIDDULPHIA
14. Euglena:
Thallus Structure:
Plants are unicellular, fusiform to acicular in shape with posterior pointed end. Each cell has a prominent gullet at the anterior end and one to several contractile vacuoles adjoining the reservoir. Cell protoplasm contains a few discoid chloroplasts with pyrenoids. Cells are uniflagellate and have a conspicuous eye spot on the lateral wall of the anterior part (Fig 2.14).
Identification:
Plants unicellular, flagellate, free-living and naked, reserve food is paramylum.
CLASS: EUGLENOPHYCEAE
Cells flagellate, flagella anteriorly attached, motile form.
ORDER: EUGLENALES
Cell having chloroplasts with pyrenoids, presence of an eye spot on the anterior lateral wall.
FAMILY: EUGLENACEAE
Cells fusiform with posterior pointed end, presence of a prominent anterior gullet.
GENUS: EUGLENA
15. Chlamydomonas:
Thallus Structure:
Plant is unicellular. The vegetative cell is spherical to ellipsoidal or pear-shaped. The cell is surrounded by a cell wall which is differentiated into firmer and mucilaginous portions. The cell contains the following parts (characteristics not visible under ordinary microscope have also been included).
i. A single large cup-shaped chloroplast, occupying most of the cell, opening at the top and much thicker at the base than elsewhere,
ii. A large pyrenoid embedded in the lower part of the chloroplast,
iii. A single nucleus,
iv. Two contractile vacuoles, situated in the anterior colourless cytoplasm,
v. An eyespot, situated anteriorly,
vi. A pair of flagella of equal length, attached anteriorly (visible under dark field illumination) (Fig 2.15).
Reproductive Structure:
There may be presence of daughter cells grouped together within the mother cells. This is called ‘palmella’ stage. This is a kind of asexual mode of reproduction, [Sexual reproduction not ordinarily visible].
Identification:
Thallus green, chloroplast always possesses pyrenoid (i.e., starch – protein aggregation). Presence of cellulosic cell wall.
CLASS: CHOLOPHYCEAE
Thallus unicellular to colonial, vegetative cells motile, chloroplast cup shaped.
ORDER: VOLVOCALES
Vegetative body unicellular and motile biflagellate, flagella whiplash type and equal in length.
FAMILY: CHLAMYDOMONADACEAE
Vegetative cells spherical to pear-shaped, each cell contains a large cup shaped chloroplast with pyrenoid, uninucleate, presence of an eyespot anteriorly, presence of palmella stage.
GENUS: CHLAMYDOMONAS
16. Volvox:
Thallus Structure:
Thallus is colonial and colony is hollow and spherical in shape. The colonial thallus (i.e. cocnobium) is composed of thousands of small head like spherical cells. Each cell has a cup-shaped chloroplast, single nucleus and contractile vacuoles. In general, cells are arranged in a single layer joined together by fine strands of cytoplasm. The spherical cells of the colonies are biflagellate. There may be presence of daughter colonies within a mother colony.
Reproductive Structure:
Within the coenobium, there are some specialised and larger cells called ‘gonidia’ which are responsible for the production of daughter colonies asexually or used for sex organ development (Figs 2.16 & 2.17).
Identification:
Thallus green, chloroplast always possesses pyrenoid (i.e., starch protein aggregation). Presence of cellulose cell wall.
CLASS: CHOLOPHYCEAE
Thallus unicellular to colonial, vegetative cells motile, chloroplast cup-shaped.
ORDER: VOLVOCALES
Vegetative body unicellular, motile and biflagellate; flagella whiplash type and equal in length.
FAMILY: VOLVOCACEAE
Coenobium hollow and spherical in shape composed of a large number of cells which are held together by cytoplasmic connections.
GENUS: VOLVOX
17. Ulothrix:
Thallus Structure:
The plant body is un-branched, simple and filamentous. The filament consists of a single row of cells, differentiated into base and apex. It is anchored to the substrate at the lower end by a specialized basal cell called holdfast.
Vegetative cells are cylindrical and contain single nucleus, a band-shaped (girdle-shaped) or plate-like parietal chloroplast with pyrenoids. Each chloroplast resembles a slightly open ring curved to fit the rounded contour of the cell (Fig 2.18).
Reproductive Structure:
Asexual Zoospore or gamete formation is rarely noticed.
Identification:
Thallus green, chloroplast always possesses pyrenoids, presence of cellulose cell wall.
CLASS: CHLOROPIIYCEAE
Thallus un-branched, filamentous, cells having parietal or girdle-shaped chloroplast with pyrenoids.
ORDER: ULOTRICIIALES
Thallus simple, un-branched, filamentous; is being differentiated into base and apex.
FAMILY: ULOTRICHACEAE
Vegetative cells cylindrical contain a large plate or band-like chloroplast with pyrenoids, each chloroplast resembles a slightly open ring curved to fit the rounded contour of the cell.
GENUS: ULOTHRIX
18. Cladophora:
Thallus Structure:
The plant body is filamentous. Filaments are branched with numerous cross walls separating the coenocytic protoplasmic segments. Branches arise just beneath a septum resulting in the appearance of dichotomy. Elongated cells with thick and distinctly stratified walls are often encrusted with carbonate of lime.
In mature cell, cytoplasmic strands traverse the large central vacuole. Each cell contains a reticulate (or numerous discoid) chloroplast bearing pyrenoids and many nuclei. The basal cell is modified into a rhizoidal cell (Fig 2.19).
Reproductive Structure:
Asexual reproduction occurs by zoospores. Cells of the finer branches of the thallus produce numerous, small, pear-shaped zoospores.
Identification:
Thallus green, chloroplast always with pyrenoids, presence of cellulose cell wall.
CLASS: CHLOROPHYCEAE
Plants branched, filamentous, filament uniseriate, cells thick-walled with multinucleate vacuolated cytoplasm and pyrenoid containing reticulate chloroplasts.
ORDER: CLADOPHORALES
Un-branched, uniseriate, filamentous plant body with rectangular cells containing coenocytic protoplasm and reticulate chloroplast.
FAMILY: CLADOPHORACEAE
Cell wall thick and distinctly stratified, branches arise just beneath a septum resulting in the appearance of dichotomy; numerous, small, pear-shaped zoospores formed from cells of finer branches.
GENUS: CLADOPHORA
19. Draparnaldia:
Thallus Structure:
The plant body is branched, filamentous and hetcrotrichous. The main axis is composed of large, more or less barrel-shaped cells. Lateral branches are composed of somewhat rectangular cells. Each cell contains a barrel-shaped chloroplast having toothed edges forming a girdle in the equatorial region.
The chloroplasts and the cells of main axis have several pyrenoids. Cells of lateral filaments are uninucleate with a parietal chloroplast having a single pyrenoid. Lateral branches are developed in clusters on the main axis in alternate or opposite or verticellate fashion. The lips of the lateral branches appear as hair-like projections – ‘setae’ (Fig 2.20).
Reproductive Structure:
Asexual reproduction occurs by zoospores. They are formed in groups of one to four in all the cells of the lateral branches. Sexual reproduction is isogamous, the gametes being formed from the cells of prostrate system.
Identification:
Thallus green, chloroplast always possesses pyrenoids, cellulose cell wall present.
CLASS: CHLOROPHYCEAE
Plant body branched, filamentous, heterotrichous, tips of the lateral branches appear as setae.
ORDER: CHAETOPHORALES
Plants branched, uniseriate, filamentous, cells having dissected plate like chloroplasts with pyrenoids.
FAMILY: CHAETOPHORACEAE
Plant body containing a main axis from which lateral branches develop in clusters in alternate or opposite or verticillate fashion.
GENUS:
DRAPARNALDIA
20. Fristchiella:
Thallus Structure:
Plant body is highly developed and heterotrichous which is differentiated into 4 zones
(a) A distinctly separate rhizoidal system consisting of downwardly directed rhizoid-like filaments composed of elongated, colourless cells joined end to end;
(b) A prostrate system of rounded or irregularly swollen clusters of cells appearing to serve the purpose of perennation;
(c) A primary projecting system having short-celled branched threads; and
(d) A secondary projecting system being composed of a lull of slightly elongated branches with longer cells.
All the cells of the plant body are uninucleate. The cells of the rhizoidal system have scanty contents. The secondary projecting system has cells with dense content having curved plate-like chloroplast containing two to eight pyrenoids each (Fig 2.21).
Reproductive Structure:
Asexual reproduction is by swarmers developed from the cells of prostrate system. Sexual reproduction is isogamous, the gametes being formed from the cells of prostrate system.
Identification:
Thallus green, chloroplast always possesses pyrenoids, presence of cellulose cell wall.
CLASS: CHLOROPHYCEAE
Plant body branched, filamentous, heterotrichous, tips of the lateral branches appear as setae.
ORDER CIIAETOPHORALES
Plants branched, uniseriate, filamentous, cells having dissected plate like chloroplasts with
pyrenoids.
FAMILY: CHAETOPHORACEAE
Presence of highly, developed heterotrichous plant body, differentiated into 4 zones, viz. rhizoidal zone, prostrate zone, primary and secondary projecting zones.
GENUS: FRITSCHIELLA
21. Coleochaete:
Thallus Structure:
The plant is hemispherical, cushion-shaped and composed of prostrate threads with branches distinct from one another exhibiting apical growth. It may also form a one layered parenchymatous disc of laterally opposed branches. The thallus is enveloped in mucilage and bears long un-branched setae. The cells are uninucleate with a single large parietal chloroplast containing one or two pyrenoids.
Reproductive Structure:
Asexual reproduction is by zoospores produced singly in thallus cells.
Oogonium:
It is a flask-shaped structure with a swollen base and borne terminally on short branches of the projecting system.
Antheridium:
It is developed in clusters at the ends of the projecting branches.
Spermocarp:
It is roundish and reddish brown in colour and composed of a central zygote surrounded by pseudoparenchymalous investments (Fig 2.22).
Identification:
Thallus green, chloroplast always possesses pyrenoids, presence of cellulose cell wall.
CLASS: CHLOROPHYCEAE
Plant body branched, filamentous, heterotrichous, tips of the lateral branches appear as setae.
ORDER: CHAETOPHORALES
Plant body represented by prostrate system with long setae, cells with parietal chloroplast, Oogonia with long neck (trichogyne), spermocarp surrounded by envelope.
FAMILY: COLEOCHAETACEAE
Thallus enveloped by a mucilage and bears long un-branched setae; sex organs on short branches; spermocarp roundish.
GENUS: COLEOCHAETE
22. Trentepohlia:
Thallus Structure:
Thallus appears to be orange red in colour. The plant body is composed of branched heterotrichous filaments. Both erect and prostrate systems are seen with branching of filaments. The cells of the filaments are cylindrical to barrel-shaped.
Each cell possesses a few discoid chloroplasts without pyrenoids and a nucleus. There is characteristic orange red colouration of the thallus and so also the cells due to the presence of haematochrome pigments. The apical cell of the filament is covered often by pectosse cap.
Reproductive Structure:
Two types of sporangia are present as asexual reproductive organs: sessile sporangia and stalked sporangia.
Sessile Sporangia:
The position varies from terminal, lateral, intercalary to axillary. It is mostly formed on prostrate branches.
Stalked Sporangia:
These are terminal and/or lateral in position and mostly found on the erect system of branches. Sporangia contain swarmers of zoospores (Fig 2.23).
Identification:
Thallus brick-red to greenish, chloroplast possesses pyrenoids, presence of cellulose cell wall.
CLASS: CHLOROPHYCEAE
Thallus filamentous; filaments branched and heterotrichous; cell cylindrical, uninucleate and contain a few discord or laminate chloroplasts.
ORDER: CHAETOPHORALES
Thallus having most prostrate and erect systems, presence of specialized adaptation for desiccation e.g., apical pectose cap, presence of varied types of sporangia.
FAMILY: TRENTEPHOLIACEAE
Thallus orange – red in colour, filaments branched (both prostrate and erect part), presence of rows of pectose caps on the apical cells of the erect filaments, sporangium globose or flat-shaped.
GENUS: TRENTEPOHLIA
23. Oedogonium:
Thallus Structure:
The plant body is composed of un-branched filaments. Each filament is again composed of a number of cylindrical or rectangular cells arranged end to end. The basal cell is modified into holdfast for attachment with the substratum. The basal cell is modified into holdfast for attachment with the substratum.
Each cell consists of large nucleus, single reticulate chloroplast with pyrenoids. In some cells of the filaments there is presence of characteristic apical rings or caps towards the upper end which is formed during intercalary division of the cells.
Reproductive Structure:
Asexual reproduction occurs by zoospores which are developed singly in zoosporangia. Zoospores are multi-flagellate. Sexual reproduction is oogamous. Species may be homothallic or heterothallic. Species may be of a macrandrous type with antheridia produced in normal filaments and nanandrous type with antheridia in special dwarf male filaments or nanandria.
In homothallic species – the antheridia are produced in rows in-between vegetative cells. The antheridia are biscuit-shaped with two antherozoids in each. The Oogonium is also intercalary in position. The subtending cell is called suffultory cell. The oogonium is large, round or oval and contains a single large egg. It has a transverse pore towards the upper side. The oospore has a thick wall. The Oogonia may be solitary or in rows.
In heterothallic nanandrous type the sporangia are developed in intercalary position and resemble the antheridia in appearance. Each forms a single androspore (not visible usually). The Andros pores germinate on the suffultory cells or on the oogonia and produce dwarf male filaments. This is a short filament producing two antherozoids apically. The oogonia are produced in the same way as in macrandrous species (Fig 2.24).
Identification:
Thallus green, chloroplast possesses pyrenoid, presence of cellulose cell wall.
CLASS: CHLOROPHYCEAE
Thallus filamentous, filament un-branched, attached to the substratum by holdfast, cells rectangular with reticulate chloroplast, growth by intercalary cell division, oogamous types of sexuality.
ORDER: OEDOGONIALES
Cells of the filaments are cylindrical, reproductive cells are intercalary in position.
FAMILY: OEDOGONIACEAE
Cells with apical rings or caps, antheridia develop in cluster, but oogonia solitary (usually).
GENUS: OEDOGONIUM
24. Zygnema:
Thallus Structure:
The plant body is un-branched filamentous and not differentiated into base and apex. Filaments are composed of rectangular cells joined end to end. Each cell contains a paired stellate chloroplast, cytoplasm in-between the two chloroplast.
Reproductive Structure:
Sexual reproduction is isogamous and occurs by conjugation between two gametes lying in two opposing filaments by means of a conjugation tube. Conjugation is usually scalariform and sometimes lateral. Zygospore is large, round, thick-walled and lies in one of two conjugating filaments or in the conjugating tube (Fig. 2.25).
Identification:
Thallus green, chloroplast possesses pyrenoids, presence of cellulose cell wall.
CLASS: CHLOROPHYCEAE
Presence of distinct conjugation by iso-gametangial fusion.
ORDER: CONJUGALES
Plant body multicellular, filamentous, filament un-branched.
FAMILY: ZYGNEMATACEAE
Cell containing a pair of stellate chloroplasts with pyrenoids. Zygospore thick-walled and rounded in shape.
GENUS: ZYGNEMA
25. Cosmarium:
Thallus Structure:
The plant body is unicellular and non-motile. Cells are of a very characteristic type, i.e., each cell has two halves or semi-cells joined by a constriction zone called sinus and a narrow connecting zone called isthmus. The surface of the cell appears to be smooth to slightly ornament. Each semi-cell contains a large star-shaped chloroplast with pyrenoids. The nucleus lies in the isthmus zone.
Reproductive Structure:
Sexual reproduction occurs by conjugation. Vegetative cells conjugate in pairs within a mucilaginous sheath to form zygospore. Zygospore is surrounded by a thick wall (Fig. 2.26).
Identification:
Thallus green, chloroplast always possesses pyrenoids (i.e., starch-protein aggregation). Presence of cellulose cell wall.
CLASS: CHLOROPHYCEAE
Plant body unicellular or filamentous, cells with star-shaped or spiral chloroplast, sexual reproduction by conjugation only.
ORDER: CONJUGALES
Plant body unicellular, each cell possessing two lobed or stellate or star-shaped chloroplasts.
FAMILY: DESMIDIA CEAE
Cell contains two halves or semi-cells connected by isthmus zone.
GENUS: COSMARIUM
26. Caulerpa:
Thallus Structure:
The plant body is differentiated into prostrate portion represented by creeping rhizome with rhizoids and an aerial portion represented by flat blade-like branched structure, the assimilator.
Internally, the plant body is characterized by the complete absence of separation and is composed of closely opposed and intertwined coenocytic threads traversed by longitudinal and transverse skeletal strands to increase the rigidity of the plant body. As such, the entire plant body is a single multinucleate cell with a central vacuole and lining cytoplasm with numerous discoid chloroplasts (Fig 2.27).
Reproductive Structure:
(Usually not found). Sexual reproduction is iso-or anisogamous. Swarmers (gametes) are formed in the entire plant body except rhizoids end are liberated through papillae.
Identification:
Thallus green, chloroplast possesses pyrenoid (i.e. starch-protein aggregation), presence of cellulose cell wall.
CLASS: CHLOROPHYCEAE
Presence of branched filamentous plant body with coenocytic cytoplasm.
ORDER: SIPHONALES
Plant body coenocytic, branched, filamentous and differentiated into rhizoidal, stoloniferous and erect portions.
FAMILY: CAULERPACEAE
Plant body differentiated into creeping rhizome zone and aerial flat blade like branched zone, presence of longitudinal skeletal strands for rigidity of the plant body.
GENUS: CAULERPA
27. Chara:
Thallus Structure:
The plant body is slender and flexuous, with individual plants attaining lengths up to 30 cm. or more. The thallus has an erect main axis differentiated into a regular succession of nodes and internodes with whorls of lateral branches of limited growth, often termed as ‘leaves’, arising from the nodes.
Branches of limited growth having nodes and internodes just like the main axis may arise axillary to the leaves. The internode is composed of a central cylindrical cell which is many times longer than broad and en-sheathed by elongated narrow cells arising from basal nodes constituting the cortex. The lowest node develop dome multicellular rhizoids.
Reproductive Structure:
There are to specialized sex organs, viz. globule (i.e. antheridium) and nucule (i.e., oogonium). They are always borne at the nodes with a definite orientation, the nucule lying above the globule.
Globule:
A mature globule is large, stalked, spherical in structure and bright yellow to red in colour. The wall of the globule is composed of eight curved plates, the shield cells, joined end to end, giving the wall a pseudo-cellular appearance.
Nucule:
It is a stalked oval structure being surrounded by an envelope of five long filaments placed side by side arranged spirally exhibiting a twisted appearance and affording protection to the oogonium. At the top of the nucule there is a conspicuous crown or corona, which is composed of 5 cells (Fig 2.28).
Identification:
Presence of differentiated plant axis containing nodes with lateral branches and internodes, reproductive organs complex with outer sterile covering.
CLASS: CHAROPHYCEAE
Comparatively complex plant body being differentiated into root-like, shoot-like or leafy zones, sex organs stalked, multicellular with sterile jackets.
ORDER: CHARALES
Elaborately developed sex organs arising in pairs from nodes.
FAMILY: CHARACEAE
Sex organs develop from nodes in pairs in a definite sequence, i.e. nucule lying above the globule, nucule possesses characteristic 5-celled corona.
GENUS: CHARA
28. Nitella:
Thallus Structure:
The plant body has the appearance of a miniature horsetail. There is a main axis with alternate nodes and internodes. The nodal zone bears a whole of lateral branches, often called ‘leaves’; branches of limited growth with nodes and internodes just like the main axis may arise axillary to the leaves.
The internode has a central cylindrical cell which is many times longer than broad and en-sheathed by elongated narrow cells arising from basal nodes forming the cortex. The lowest node develops some multicellular rhizoids.
Reproductive Structure:
The lateral branches bear the reproductive organs, the globule and nucule. They are juxtaposed, the globule being directed upwards and a pair of nucleus downwards. The globule is rounded, but nucule is somewhat short and oval with a roundish crown of ten cells in two tires and is relatively short. Other features of nucule and globule art- similar to those of Chora (Fig 2.29).
Identification:
Presence of differentiated plant axis containing nodes with lateral branches and internodes, reproductive organs complex with outer sterile covering.
CLASS: CHAROPHYCEAE
Comparatively complex plant body being differentiated into root-like, shoot-like or leafy zones, sex organs stalked, multicellular with sterile jackets.
ORDER: CHARALES
Elaborately developed sex organs arising from nodes in pairs.
FAMILY: CHARACEAE
Presence of a pair of nucleus and a globule in juxtaposed position on lateral branches, the globule being directed upwards and the nucleus downwards, presence of ten-celled rounded two-tired crown on the tip of nucule.
GENUS: NITELLA
29. Vaucheria:
Thallus Structure:
The thallus consists of a long, tubular, sparingly branched filament. The filament is coenocytic and multinucleate cytoplasm. The central portion of the filament is occupied by a large vacuole. The cytoplasmic layer is composed of many small disk-shaped or elliptical chloroplasts with no pyrenoids. The cytoplasm also contains many oil globules. Thallus is yellowish green in colour.
Reproductive Structure:
There are two kinds of sex organs, antheridium and oogonium, produced on short branches and then lying close together.
Antheridium:
It is a slender curved hook-like tubular structure which is walled off from the rest of the filament.
Oogonium:
It is a spherical or oval shaped, sessile or short stalked body with a sub-apical beak. The oospore lies within the oogonium and is thick-walled (Fig 2.30).
Identification:
Thallus yellowish-green in colour, filamentous, coenocytic, branched; presence of oil as reserve food, sexual reproduction complex oogamous type.
CLASS: XANTHOPHYCEAE
Plant body coenocytic, filamentous, asexually reproduced by multi-flagellated zoospores.
ORDER HETEROSIPHONALES
Filaments irregularly branched, antheridia cylindrical, curved, Oogonia round to oval.
FAMILY: VAUCHERIACEAE
Filaments long, tubular, sparingly branched, antheridia hook-like curved, oogonia sessile or short-stalked with a beak.
GENUS: VAUCHERIA
30. Botrydium:
Thallus Structure:
The plant body is differentiated into a pear shaped or vesicular lobed aerial portion (assimilator) and a branched root-like underground rhizoidal portion. The plant body is coenocytic and cytoplasm contains many nuclei, lenticule to fusiform plastids, oil droplets and granules. The rhizoidal portion is without plastids.
Reproductive Structure:
The mature thalli, the protoplast of aerial vesicle migrates into the rhizoidal portion and collects at the ends of the rhizoids which become inflated and swell to develop into rounded thick-walled tubers or cysts or coenocysts (Fig 2.31).
Identification:
Thallus yellowish – green in colour, filamentous, coenocytic, branched, presence of oil as reserve food, sexual reproduction complex oogamous type.
CLASS: XANTHOPHYCEAE
Plant coenocytic, balloon-shaped to filamentous, oil as reserve food present.
ORDER: HETEROSIPHONALES
Plant body characterised by unicellular multinucleate vesicular lobed aerial portion and a colourless rhizoidal portion.
FAMILY: BOTRYDIACEAE
Plant body differentiated into vesicular lobed aerial portion and branched root like rhizoidal portion.
GENUS: BOTRYDIUM
31. Ectocarpus:
Thallus Structure:
The plant body is composed of irregularly prostrate portion and profusely branched filaments which grow upright in tufts. The mature portion of the thallus is multi-axial and pseudoparenchymatous. The ultimate branchlets of the erect portion are uniseriate and attenuated to an acute point. The branchlet cells are uninucleate and contain plate like or band-shaped chloroplasts. The thallus is brownish in colour.
Reproductive Structure:
(a) Plurilocular Gametangia:
Conspicuous plurilocular gametangia are present on tips of the lateral branchlets (of haploid plants). The plurilocular gametangium is a narrow, elongated structure with a number of small compartments.
(b) Unilocular Sporangia:
There are some filaments which possess more or less oval unilocular sporangia that are developed with an enlargement of the terminal cells of short lateral branchlets (diploid plant). Each sporangium contains a number of zoospores.
(c) Plurilocular Sporangia:
Diploid plants also develop plurilocular sporangia which are morphologically similar to plurilocular gametangia (Fig 2.32).
Identification:
Thallus brownish in colour, much branched, filamentous; branchlets attenuated, cells with single nucleus and chloroplasts devoid of pyrenoids.
CLASS: PHAEOPHYCEAE
Mature portion of the thallus multi-axial and pseudoparenchymatous.
ORDER: ECTOCARPALES
Filamentous, branched plant body, gametangia or sporangia borne at the tips of the branchlets.
FAMILY: ECTOCARPACEAE
Gametangia pleurilocular, elongated, borne on the tips of the lateral branches, presence of globose unilocular sporangia with a few spores.
GENUS: ECTOCARPUS
32. Dictyota:
Thallus Structure:
The plant body is thalloid differentiated into a prostrate and erect portion. The prostrate portion of the thallus is represented by cylindrical rhizome which affords anchorage to the substratum. The fan-shaped upright position of the thallus is dichotomously branched.
The upright portion has a lower cylindrical stalk-like structure gradually expanding into a dichotomously branched ribbon like part. A mature thallus consists of a middle layer of large colourless cells bounded externally by a layer of small assimilating cells, densely packed with chromatophores.
Reproductive Structure:
Asexual Reproduction:
Asexual reproduction is by tetraspores produced in tetrasporangia. Tetrasporangia are produced singly or in groups on both surfaces of sporophyte. The tetra-sporangium has a short basal stalk and round body containing four tetraspores.
Sexual Reproduction:
Sex organs, i.e. antheridia and oogonia are formed in clusters or sori just outside the thallus surface of gametophytic plants. Antheridia are produced in groups of 100 to 200. Each antheridium is shortly stalked and elongated. The number of oogonia in a sorus may be up to 10. Each oogonium has a short one-celled stalk and is slightly elongated (Fig 2.33).
Identification:
Thallus brownish in colour, much branched, thalloid, macroscopic; cells with single nucleus and chloroplasts devoid of pyrenoids.
CLASS: PHAEOPHYCEAE
Plant body thalloid, thallus ribbon shaped and branched, presence and antheridium and oogonium as sex organs.
ORDER: DICTYOTALES
Plant body branched, ribbon-shaped thalloid, sex organs borne superficially on thallus.
FAMILY: DICTYOTACEAE
Upright portion of the thallus dichotomously branched, sex organs developed in cluster or sori.
GENUS: DICTYOTA
33. Fucus:
Thallus Structure:
The plant consists of a leathery parenchymatous, dichotomously branched ribbon like frond, stem-like stipe and a basal disc-like holdfast or hapteron by which it is attached to the substratum. The thallus possesses bladder-like air vesicles which remain scattered. The swollen tips of the thalli bear conceptacles containing sex organs.
In T.S. through the thallus, there are three distinct layers – outer cuticularised limiting layer, middle cortical layer and innermost medullary layer.
Reproductive Structure:
Sex organs are localised within the cavities i.e., conceptacles. Conceptacles are somewhat rounded with an opening called ostiole, which is guarded by sterile filaments called paraphyses. Within the cavity, antheridia or stalked oogonia are arranged along with paraphyses.
Antheridium:
Antheridia are very small and borne in clusters on very short and much branched hairs along with hair-like paraphyses.
Oogonium:
It is stalked, globose, borne single along with paraphyses. Each oogonium contains 8 eggs (Fig 2.34).
Paraphyses:
They are uniseriatc, septate, filamentous. Two kinds of sex organs developed on separate conceptacles. Sexual reproduction is oogamous.
Identification:
Thallus, brownish in colour, much branched, macroscopic thalloid cells uninucleate, chloroplast devoid of pyrenoids.
CLASS: PHAEOPHYCEAE
Plants leathery, dichotomously branched, differentiated into holdfast, stips and blade, sex organs developed within conceptacles.
ORDER: FUCALES
Plant body with air bladders, receptacles – lie on terminal parts of the thalli, sexual reproduction, oogamous, oogonium with a few eggs.
FAMILY: FUCACEAE
Antheridia on branched hairs and mixed with hair-like paraphyses, oogonia oval, stalked, solitary and intermingled with paraphyses.
GENUS: FUCUS
34. Sargassum:
Thallus Structure:
The plant body has a stem-like axis and leaf like blades. The thallus bears an axis with alternate, flat, costate branches. The branches have short, phyllode-like or leaf-like structures called ‘leaves’ which may or may not have midrib. The secondary branches are reduced to air-bladders. In the pair like tertiary or receptacular branches, flask-shaped conceptacles are embedded.
In T.S. through the main axis, three major zones are noticed – limiting layer, cortex and medulla.
Reproductive Structure:
Antheridia and oogonia are borne in flask shaped conceptacles on the receptacular branches. Plants may be monoecious or dioecious.
Antheridium:
They occur in clusters along with paraphyses. Mature antheridia are ovoid structures.
Oogonium:
They are sessile and borne directly on the wall of the conceptacle. Each oogonium has a single egg.
Paraphyses:
They are uniseriate, septate and filamentous (Fig. 2.35).
Identification:
Thallus brownish in colour, macroscopic, thalloid, cells uninucleate, chloroplast devoid of pyrenoids.
CLASS: PHAEOPHYCEAE
Plants leathery, dichotomously branched, differentiated into holdfast, slips and blade, sex organs developed within conceptacles.
ORDER: FUCALES
Plant body with air bladders, receptacles – lie on terminal parts of the thalli, sexual reproduction, oogamous, ooganium with a few eggs.
Plant possesses flat costate branches; conceptacles develop on special branches, each oogonium with single egg.
FAMILY: SARGASSACEAE
Lateral branches of the thallus phyllode like, some branches bear air bladders and some receptacles; conceptacles flask-shaped with antheridia or oogonia or both.
GENUS: SARGASSUM
35. Batrachospermum:
Thallus Structure:
The plant body is of gelatinous texture appearing as chains of delicate beads. The primary axis is multi-axial and consists of a large number of elongated cylindrical cells placed end to end in a single row.
Numerous branches arise in whorls from the upper ends of the cells just below the septa. This peculiar arrangement of the branches has caused the main axis to be differentiated into nodes and internodes. Cells are uninucleate containing a few parietal, lobed chloroplasts with pyrenoids.
Reproductive Structure:
Sexual reproduction is oogamous. Plants may be monoscious or dioecious.
Cystocarp:
It is somewhat globose in structure and composed of several gonimoblast filaments surrounded by enveloping threads. The terminal cells of the filaments produce carposporangia with carpospores.
Antheridia or Spermatangia:
They are unicellular spherical structures borne in clusters at the tips of lateral branches of thallus and contain single male gamete or spermatium (Fig 2.36).
Identification:
Presence of gelatinous material in the thallus, cells contain chloroplasts with pyrenoids, presence of characteristic post-zygotic structure called cystocarp.
CLASS: RHODOPHYCEAE
Well-developed branched filamentous thallus, carposporangia developing on filamentous gonimoblasts.
SUB CLASS: FLORIDEAE
Plant body heterotrichous, uniaxial in the growing and multi-axial in the mature region; carposporangia developing on filamentous gonimoblasts derived directly from the fertilised carpogonium.
ORDER: NEMALIONALES
Plant body soft, thick, gelatinous branched thallus being differentiated into structures resembling nodes and internodes branches arise in whorls from the nodes; terminal cell of the gonimoblast filament produces carpospore.
FAMILY: BATRACHOSPERMACEAE
Main axis of the thallus differentiated into nodes with whorls of branches, presence of cystocarp with carposporangia.
GENUS: BATRACHOSPERMUM
36. Polysiphonia:
Thallus Structure:
The plant body is filamentous, branched laterally or dichotomously and brownish-red to purple red in colour. The main axis and its branches possess a polysiphonous appearance as the central axial cell (siphon) is surrounded by pericentral cells (siphons) of variable number.
The cells have prominent cell to cell cytoplasmic connections and each cell has one nucleus and many discoid plastids embedded in dense cytoplasm. Ultimate branches are uniseriate structures and are known as trichoblasts.
Reproductive Structure:
Spermatangium:
The lateral branches of the male plant bear antheridia known as spermatangia in dense clusters. The spermatangia are short-stalked colourless and spherical or oval structures. It contains a single spermatium.
Cystocarp:
It is an urn-shaped structure, formed by gonimoblast filaments surrounded by sterile filaments. The terminal cells of the gonimoblast filament produce a carposporangium with one carpospore.
Tetrasporangia:
It is borne on the central axis of the specialised filament called tetrasporophytic filament. Each sporangium contains four tetraspores (Fig. 2.37).
Identification:
Presence of gelatinous material in the thallus, cells contain chloroplasts with pyrenoids, presence of characteristic post-zygotic structure called cystocarp.
CLASS: RHODOPHYCEAE
Well-developed branched filamentous thallus, carposporangia developing on filamentous gonimoblasts.
SUB CLASS: FLORIDEAE
Plant body heterotrichous, uniaxial in the growing and multi-axial in the mature region; carposporangia developing on filamentous gonimoblasts derived directly from the fertilised carpogonium, Uni- or multi-axial construction of thallus, presence of tetrasporangia with tetraspores.
ORDER: CERAMIALES
Polysiphonous, branched thallus, cystocarp, Urn-shaped with a pore, tetrasporangia with tetraspores.
FAMILY: RHODOMELACEAE
Cells of the central axis polysiphonous, surrounded by pericentral cells, presence of spermatangium, cystocarp and tetrasporangia on separate filaments.
GENUS: POLYSIPHONIA
37. Compsopogon:
Thallus Structure:
The plant body is filamentous and branched. The younger parts of the filament are uniseriate with discoid cells and the mature parts are with an axial row of cells which become greatly enlarged being barrel-shaped and surrounded by one or more layers of cortical cells. Cells of the thallus are uninucleate containing numerous spherical chromatophores which are densely aggregated towards the cell wall. There are no pit connections between the adjacent cells.
Reproductive Structure:
Microsporangia – Sporangia are developed in clusters from cortical cells of the filament in the mature region. Sporangial clusters or sori are more or less hemispherical to oblong in shape and consist of 15-25 or more microsporangia. The microsporangia develop non-flagellate, spherical mono-spores. Solitary macrosporangia with one monospore are also found on the filament (occasionally) (Fig 2.38).
Identification:
Presence of gelatinous material in the thallus, cells contain choloroplasts with pyrenoids, presence of characteristic post-zygotic structure called cystocarp.
CLASS: RHODOPHYCEAE
Simple thallus with branched filamentous construction, pit connections between cells of the thallus lacking.
SUB CLASS: BANGIOIDEAE
Thallus mostly branched, filamentous, sporangia formed in sori.
ORDER: BANGIALES
Plant body branched, filamentous, reproduction mostly by spores formed within sporangia.
FAMILY: ERYTHROTRICHIACEAE
Plant body copiously branched, filamentous, microsporangia borne in clusters on the mature portion of the thallus.
GENUS: COMPSOPOGON
