3. iii unit cbcs

Department of Botany B.Sc (Bot) First Year First Sem Notes (UNIT-III) Phycology
S.R.R. Govt. Arts & Science College Karimnagar-505001 Prepared By Dr.T.Ugandhar
45
General Characters of Algae
Salient Features
1. In Algae the plant body shows no differentiation into root, stem or leaf or true tissues.
Such a plant body is called thallus.
2. They do not have vascular tissues. The sex organs of this group of kingdom plantae are
not surrounded by a layer of sterile cells.
3. Algae are autotrophic organisms and they have chlorophyll. They are 02 producing
photosynthetic organisms that have evolved in and have exploited an aquatic
environment. The study of Algae is known as Algology or Phycology.
Occurrence and Distribution
i) Most of the algae are aquatic either fresh water or marine. Very few are terrestrial. A few
genera grow even in extreme condition like thermal springs, glaciers and snow.
ii) The free floating and free swimming minute algae are known as phytoplanktons. Species
that are found attached to the bottom of shallow water along the edges of seas and lakes are
called Benthic.
iii) Some of the algae exhibit symbiotic association with the higher plants. Some species of
algae and fungi are found in association with each other and they are called Lichens. A few
species of algae are epiphytes (i.e they live on another plant or another alga) and some of
them are lithophytes (i.e they grow attached to rocks)
Thallus organization
i) The thalli of algae exhibit a great range of variation in structure and organization. It ranges
from microscopic unicellular forms to giant seaweeds like Macrocystis which measures up to
100 meters long. Some of them form colonies, or filaments.
ii) The unicellular form may be motile as in Chlamydomonas or non-motile as in Chlorella.
Most algae have filamentous thallus. eg. Spirogyra.
iii) The filaments may be branched. These filamentous form may be free floating or attached
to a substratum. Attachment of the filament is usually effected through a simple modification
of the basal cell into a holdfast. Some of the Algae are
macroscopic. eg. Caulerpa, Sargassum, Laminaria,
Fucus etc. where the plant body is large. In Macrocystis
it is differentiated into root, stem and leaf like structures.
iv) The chlroplasts of algae present a varied structure.
For eg they are cup shapedin Chlamydomonas, ribbon-
like in Spirogyra and star shaped in Zygnema.
Cell Structure & Pigmentation
i) The exception of blue green algae which are treated as
Cyanobacteria, all algae have eukaryotic cell
organization. The cell wall is made up of cellulose and
pectin. There is a well defined nucleus and membrane
bound organelles are found. Three types of
Photosynthetic pigments are seen in algae. They are
1. Chlorphylls 2. Carotenoids 3. Biliproteins.
ii) While chlorophyll a is universal in all algal classes,
chlorophyll b,c,d,e are restricted to some classes
of algae The yellow, orange or red coloured pigments are
called carotenoids. It includes the caroteins and the
Xanthophylls.
Thallus Organization in Algae (1.Chlamydomonus 2) Volvox 3) Spirogyra 4)
Gelidium 5) Chondrus 6) Macrocystatis 7) Sargassum

46
iii) The water soluble biliproteins called phycoerythrin (red) and phycocyanin (blue) occur
generally in the Rhodophyceae and Cyanophyceae and the latter is now called
cyanobacteria.
iv) These pigments absorb sunlight at different wavelengths mainly in blue and red range and
help in photosynthesis.
v) Pigmentation in algae is an important criterion for classification. The colour of the algae is
mainly due to the dominance of some of the pigments. For example in red algae(class
Rhodophyceae) the red pigment phycoerythrin is dominant over the others.
vi) The pigments are located in the membranes of chloroplasts. In each chloroplast one or few
spherical bodies called pyrenoids are present. They are the centres of starch formation.
Nutrition and reserve food materials in Algae
Algae are autotrophic in their mode of nutrition. The carbohydrate reserves of algae
are various forms of starch in different classes of Algae. For example, in Chlorophyceae, the
reserve food is starch and in Rhodophyceae it is Floridean starch, in Phaeophyceae it is
laminarian starch while in Euglenophyceae it is paramylon. Members of Phaeophyceae
store mannitol in addition to carbohydrate.
Members of Xanthophyceae and Bacillariophyceae store fats, oils and lipids. The
nature of reserve food material is also another important criterion used in classification.
Arranagement of Flagella
i) Flagella or cilia( sing.flagellum / cilium) are organs of locomotion that occur in a
majority of algal classes.
ii) There are two types of flagella namely whiplash (Acronematic) and tinsel
(pantonematic).
iii) The whiplash flagellum has a smooth surface while the tinsel flagellum has fine
minute hairs along the axis.
iv) The number, insertion, pattern and kind of flagella appear to be consistent in each
class of algae and it is an important criterion for classification of algae. Motile cells
of the Algae are typically biflagellate. When both flagella are of equal length and
appearance, they are described as isokont. Heterokont forms have dissimilar flagella
with reference to their length and types.
Types of Whiplash Flagella
v) Red algae(Rhodophyta) and Blue green algae(Cyanophyta) lack flagella. Each
flagellum consists of two central microtubles surrounded by a peripheral layer of nine doublet
microtubles. This is called 9+2 pattern of arrangement which is a characteristic feature of
eukaryotic flagellum. The entire group of microtubles is surrounded by a membrane.
Reproduction
Three common methods of reproduction found in Algae are
1. Vegetative 2. Asexual and 3. Sexual
Vegetative reproduction
It lakes place by fragmentation or by the formation of adventitious branches.
Asexual reproduction:
i) It takes place by means of different kinds of spores like Zoospores, Aplanospores and
Akinetes.
ii) Zoospores are naked, flagellated and motile. eg.(Chlamydomonas) Aplanospores are thin
walled and non motile (eg Chlorella) Akineties are thick walled and non motile spores (eg
Pithophora)
Sexual Reproduction: - Sexual reproduction involves fusion of two gametes. If fusing
gametes belong to the same thallus it is called homothallic and if they belong to different
thalli it is heterothallic. Fusing gametes may be isogametes or heterogametes.

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Isogamy: - It is the fusion of two morphologically and physiologically similar gametes.eg.
Spirogyra and some species of Chlamydomonas .
Heterogamy:- This refers to the fusion of dissimilar gametes. It is of two types
1. Anisogamy 2. Oogamy
1. Anisogamy is the fusion of two gametes which are morphologically dissimilar but
physiologically similar (both motile or both non-motile)
2. Oogamy refers to the fusion of gametes which are both morphologically and
physiologically dissimilar. In this type of fusion the male gamete is usually referred to as
antherozoid which is usually motile and smaller in size and the female gamete which is
usually non- motile and bigger in size is referred to as egg. The sex organ which produces the
antherozoids is called antheridium and the egg is produced in oogonium. The fusion product
of antherozoid and egg is called Zygote. The zygote may germinate directly after meiosis or
may produce meiospores which in turn will germinate.
Classification
F.E. Fritsch (1944-45) classified algae into 11 classes in his book “Structure and
Reproduction of Algae” based on the following characteristics.
1). Pigmentation 2). Reserve food 3). Flagellar arrangement 4). Thallus organization
5). Reproduction. The 11 classes of algae are:
1. Chlorophyceae 2. Xanthophyceae 3. Chrysophyceae 4. Bacillariophyceae 5.
Cryptophyceae 6. Dinophyceae 7. Chlromonodineae 8.Euglenophyceae 9. Phaeophyceae
10. Rhodophyceae and 11. Myxophyceae
Table : Characteristics of Major Groups of Algae
Class Pigments Flagella Reserve Food
Material
Chlorophyceae
(green algae)
Chlorophyll-a,b
Carotene
XanthophyII
Two identical
flagella per cell
Starch
Xanthophyceae Chlorophyll-a, b
Carotene
XanthophyII
Heterokont type,
one whiplash
type and other
tinsel
Fats and
Leucosin
Chrysophyceae
(diatoms, golden
algae)
ChlorophyII-a, b
Carotenoids
One,two or more
unequal flagella
Oils and
Leucosin
Bacillariophyceae Chlorophyll-a, c
Carotenes
Very rare Leucosin
and fats
Phaeophyceae
(brown algae
ChlorophyII-a
Xanthophyll
Two dissimilar
lateral flagella
Laminarin,
fats
Rhodophyceae
(Red algae)
Chlorophyll-a
Phycocyanin
Phycoerythrin
Non-motile Starch
Myxophyceae Chlorophyll-a,
carotene,
phycocyanin,
phycoerythrin
Non-motile Cyanophyce
an starch

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Volvox: Occurrence, Structure and Reproduction (With Diagrams)
Volvox is represented by about 20 species:Some common Indian species are—Volvox
globator, V aureus, V. prolificus, V. africanus and V.
rousseletii
Occurrence of Volvox:
1. Volvox is free floating fresh water green algae.
2. Volvox grows as planktons on surface of water bodies like
temporary and permanent ponds, lakes and water tanks.
3. During rainy season due to its fast growth the surface of water bodies become green.
4. The Volvox colonies appear as green rolling balls on surface of water.
Structure of Volvox:
i) Volvox thallus is a motile colony with definite shape and number of cells. This habit of
thallus is called coenobium.
ii) The colony is hollow, spherical or oval in shape and the size of colony is about the size of
a pin head.
iii) The number of cells in a colony is fixed. Depending upon the species of Volvox the cells
can be 500-50,000.
iv) The central part of colony is mucilaginous and the cells are arranged in a single layer on
periphery of the colony.
v) The cells of anterior end possess bigger eye spots than those of posterior end cells.
vi) The cells of posterior side become reproductive on maturity. Thus, spherical or round
colony of Volvox shows clear polarity.
vii) The cells of Volvox colony are Chlamydomonas type. Every cell has its own mucilage
sheath.
viii) The mucilage envelope of colony appears angular due to compression between cells.

49
ix) The cells are connected to each other through cytoplasmic strands. In some species of
Volvox the cytoplasmic connections or strands are not present.
x) The cells of colony are usually pyriform with narrow anterior end and broad posterior end.
xi) The cells are biflagellate; the two flagella are equal, whiplash type and project outwards.
xii) The protoplasm of cell is enclosed within psma membrane.
xiii) Each cell contains one nucleus, a cup shaped chloroplast with one or more pyrenoids, an
eye spot and 2-6 contractile vacuoles. In some species of Volvox e.g., in V. globator and V.
rousseletii the cells are of Sphaerella type.
xiv) The cells of colony are independent for functions like photosynthesis, respiration and
excretion.
xv) The movement of colony takes place by co-ordinated flagellar movement.The
reproduction is common to the coenobium.
Reproduction in Volvox:
i) Volvox reproduces both asexually and sexually.
ii) The asexual reproduction takes place under favourable conditions during spring and early
summer.
iii) In Volvox mostly the cells of posterior part of colony take part in reproduction.
iv) These reproductive cells can be recognized by their larger size, prominent nuclei, dense
granular cytoplasm, more pyrenoids and absence of flagella (Gonidia).
Asexual Reproduction:
i) During asexual reproduction some cells of the posterior part of colony become
reproductive.
ii) These cells enlarge up to ten times, become rounded and lose flagella.
iii) These cells are called gonidia (Sing, gonidium). The gonidia lose eye spot. Pyrenoids
increase in number.
iv) The gonidia are pushed towards interior of the colony.
v) The first division of gonidium is longitudinal to the plane of coenobium and this forms 2
cells (Fig. 2 A).
.
.

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vi) The second division is also longitudinal and at right angle to the first, forming 4 cells (Fig.
2 B). By third longitudinal division all the four cells divide to make 8 cells of which 4 cells
are central and 4 are peripheral
vii) These 8 cells are arranged in curved plate-like structure and are called plakea stage (Fig.
2 C, D). Each of these 8 cells divides by longitudinal division forming 16 cells arranged in
the form of a hollow-sphere (Fig. 2 E).
viii) The sphere is open on exterior side as a small aperture called phialopore (Fig. 2 F).
ix) The cells at this stage continue to divide till the number of cells reaches the characteristic
of that species. The cells at this stage are naked and in close contact with each other. The
pointed anterior end of cells is directed towards inside.
x) The next step is called inversion of colony (Fig. 2 G-H). As cells become opposite in
direction, their anterior pointed end has to face the periphery of colony
xi) The inversion of colony starts with formation of a constriction opposite to phialopore.
xii) The cells of posterior end along with constriction are pushed inside the sphere, till the
whole structure comes out of the phialopore.
xiii) After inversion, the anterior pointed end of the cell faces periphery.
xiv) The phialopore gets closed, and makes the anterior part of the colony. After inversion the
cells develop cell wall, flagella and eye spot.
xv) The cells become separated due to development of gelatinous sheath around each cell.
This newly developed colony is called daughter colony (Fig. 2 I).
xvi) The daughter colonies initially remain attached to gelatinized wall of parent colony and
later become free in gelatinous matrix of parent colony.
xvii) The daughter colonies are released in water after the disintegration of parent colony or
through the pores.
Sexual Reproduction:
1. The sexual reproduction in Volvox is oogamous type.
2. Some species of Volvox e.g., V. globator are monoecious or homothallic (Fig. 3) i.e., the
antheridia and oogonia develop on same colony. Other Volvox species e.g., V. rousseletii
are dioecious or heterothallic i.e., antheridia and oogonia develop on different colonies.
3. Monoecious species are usually protandrous i.e., antheridia mature before oogonia but
some species are protogynous i.e., oogonia develop before antheridia. V aureus is mostly
dioecious but sometimes can be monoecious.
4. Reproductive cells mostly differentiate in the posterior part of colony. These cells
enlarge, lose flagella and are called gametangia. The male reproductive cells are called
antheridia or androgonidia and female reproductive cells are called oogonia or
gynogonidia.
Development of Antheridium:
i) The development of antheridium starts with formation of antheridial initial or
androgonidial cell mostly in posterior side of the colony.
ii) The initial cells enlarge, lose flagella, protoplasm becomes dense and nucleus becomes
larger.
iii) The antheridial initial shifts inside towards cavity and remains connected to other
vegetative cells through cytoplasmic strands.
iv) The protoplast of antheridial initial divides, longitudinally to form 16-512 elongated cells.
The cells remain in plate like structure or arrange in a hollow sphere.
v) The inversion of cells also takes place as in asexual reproduction. Each cell differentiates
in antherozoid or spermatozoid (Fig. 3, 4).
vi) The antherozoid is spindle shaped, elongated, bi-flagellated structure containing two
contractile vacuoles, nucleus, cup shape chloroplast, pyrenoid and eye spot. It is pale yellow
or green in colour.

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vii) The antherozoids are released individually or sometimes in groups.
Development of Oogonium:
i) The oogonia also differentiate
mostly in posterior side of the
colony.
ii) The oogonial initials enlarge,
nucleus becomes larger, protoplast
becomes dense, flagella are lost,
eye spot disappears and many
pyrenoids appear.
iii) The mature oosphere or ovum
is round or flask shaped structure.
The egg is uninucleate structure, the beak of flask shape oogonium functions as receptive
spot (Fig. 5 A, B).
Fertilization of Volvox:
i) After liberation from
antheridium, the anther
ozoids swim freely on
surface of water.
ii) Due to chemotactic
response the anthero
zoids reach the oogonia.
iii) Some antherozoids
enter each oogonium.
Only one antherozoid
enters inside the
oogonium through receptive spot.
iv) After this plasmogainy i.e., fusion of male and female
cytoplasm and karyogamy i.e., fusion of male and female nuclei
take place.
v) This results in formation of diploid zygote (Fig. 5 D). The
diploid zygote secretes a three layered thick wall.
vi) The layers of the wall are exospore, mesospore and endospore
(Fig. 6 A, B).
vii) The outer exospore is thick. It may be smooth e.g., V. aureus
(Fig. 6 A) or spiny e.g., V. globator (Fig. 6 B).
viii) The mesospores and endospores are thin and smooth. The
walls contain nucleus pigment haematochrome which imparts red
colour to the zygote.
x) The zygotes are released by the disintegration of parent
colony. Then zygotes undergo a period of dormancy.
Germination of Zygote:
i) The dormant zygote germinates on approach of favourable
climatic conditions.
ii) The diploid nucleus of zygote undergoes meiotic division
forming four haploid cells. The outer two layers of zygote burst
and the inner layer comes out as vesicle.
iii) The four haploid cells migrate with the vesicle (Fig. 6 C, D). The development of new
colony from zygote differs in different species of Volvox. In V. aureus and V. minor the

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protoplasm of zygote divides repeatedly until the cell number of colony is reached and new
colony is formed as in asexual reproduction process.
iv) In V. campensis the protoplast of zygote divides to make many biflagellate zoospores.
Only one zoospore survives and all other disintegrate.
v) This zoospore comes out of the vesicle it divides to make many cells which arrange to
form a colony. In V. rousseletii the zygote forms a single biflagellate zoospore; the protoplast
of zoospore divides and forms a colony.
vi) In all the methods the cells divide and undergo inversion to make a mature colony (Fig. 6
E-H).
Life Cycle of Volvox:
Volvox is haploid (n) algae, the haploid gametes fertilize to make diploid zygote (2n)
which divides by meiosis to make haploid cells (n) which mature into haploid Volvox colony
(Fig. 7, 8).
Oedogonium
Systematic Position:
Occurrence of Oedogoniales:
i) The genus Oedogonium (Oedos-swollen, gonas -
reproductive) structure is the only genus of the family
with un-branched filaments.
ii) It is represented by about 400 species.
The common Indian species are:
i) O. cardiacum. O. elegans, O. obolongellum and O. tenuis.
ii) Oedogonium occurs as the fresh water filamentous alga found in ditches, ponds, pools and
lakes. iii) It occurs as epiphytic alga found attached on leaves and twigs of other plants.
iv) It is also found attached on other algae such as Cladophora.

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v) Some species of Oedogonium are terrestrial, found growing on moist soils. It is common
in stagnant water and less common in running water.
Thallus: The thallus is made of green, multicellular un-branched filaments.
The filament is made of three types of cells (Fig. 1):
(i) The lower-most basal cell or holdfast.
(ii) The intercalary cells.
(iii) The upper-most apical cell.
Hold Fast:
i) The filament is attached by means of specially differentiated
basal cell.
ii) The holdfast is found in aquatic species and it rarely occurs in
terrestrial forms. In terrestrial forms it may give out rhizoid like
outgrowths.
iii) The hold fast or basal cell is club shaped, broad, round in
upper part and narrow in lower part.
iv) The lower terminal part of basal cells is multi-lobed, disc like
or finger shaped which attaches the filament to substratum.
Chloroplasts are absent or poorly developed in basal cell hence it
does not take part in photosynthesis.
Intercalary Cells:
i) All cells of the filament in between apical cell and the basal
cell are intercalary cells.
ii) The intercalary cells of filaments have base-apex polarity and
this is maintained even when filaments break and become free
floating.
iii) All intercalary cells are alike, only some cells after division
develop cap in upper part. Such cells are called cap cells.
Apical Cell:
i) The terminal cell of the filament called apical cell. It is
round or dome shaped. In some species e.g., O. ciliata, the
apical cell is tapering and gives rise to narrow hair like
structure. The apical cell is green due to chlorophyll and
takes part in photosynthesis.
Cell Structure of Oedogoniales:
i) The cells are elongated and cylindrical. The cell wall is
generally thick, rough and rigid. It is made up of three
concentric layers, the inner cellulose, middle pectose and
the outer layer is chitinous in nature.
ii) The protoplasm consists of thin plasma membrane,
cytoplasm, central vacuole, reticulate chloroplast and the
nucleus.
iii) The centre of the cell is occupied by a large central
vacuole which contains the cell sap. The cell sap contains
excretions, secretions and inorganic compounds. The
protoplast occurs as thin layer between the central vacuole and the inner cell wall.
iv) The chloroplast is characteristically reticulate, extending or covering the whole cell and
encircling the protoplast (Fig. 2 A, B).
v) The strands of reticulum may be broad or narrow depending upon the species. In most of
the cases the strands are parallel to the long axis of the cell. Many pyrenoids are present at the
intersections of the reticulum, Pyrenoids are covered with starch plates.

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vi) There is single large nucleus, it is biscuit shaped or biconvex and lies in the centre of cell,
internal to the chloroplast.
vii) The nucleus possesses 1-2 nucleoli, and thread like or elongated chromosomes. The cell
also contains mitochondria, Golgi bodies, endoplasmic reticulum and the other cell
organelles.
Growth:
The growth of Oedogonium filaments takes place by cell division in intercalary cells but
sometimes the apical cell also divides and takes part in the elongation of filaments.
Cell Division:
The process of cell division in Oedogonium takes place in following stages:
(i) The nucleus from periphery moves towards the centre and slightly towards the upper part
of the cell (Fig. 3 A).
(ii) Since the wall does not elongate in the usual manner, the cytoplasmic wall material
gathers in the form of a“ring” round the inner wall at the upper end of the cell (Fig. 3 A).
(iii) The nucleus divides
mitotically and there is
formation of a groove in the
ring (Fig. 3B, C).
(iv) The next stage is the
elongation or stretching of the
daughter cells by breaking up
of the wall layers round the
groove of the ring. The lower
daughter cell elongates to the
former level of the ring. The
upper one also elongates to the same extent. The process of elongation is completed within 15
minutes (Fig. 3 D).
(v) Along with the completion of elongation, a transverse wall formation between the two is
also completed. The distal end of the upper cell contains a small portion of the old parent wall
which appears as the apical cap.
Reproduction in Oedogonum
The reproduction in Oedogonium takes place by vegetative, asexual and sexual methods.
(i) Vegetative Reproduction:
Vegetative reproduction takes place by fragmentation and akinete formation.
(A) Fragmentation:
Oedogonium filament breaks into many small fragments which have capability to grow
into complete filaments under favourable conditions.
Fragmentation takes place due to any of the following reasons:
(a) Accidental breaking of the filaments.
(b) Dying or dehydration of intercalary cells.
(c) Disintegration of intercalary cells due to conversion in sporangia.
(d) Mechanical injury to the filament.
(e) Change in the environmental conditions.
(B) Akinete formation:
i) The akinetes are formed under unfavorable conditions.
ii) Akinetes are modified vegetative cells which become swollen, round or oval, reddish
brown and thick walled.
iii) These are rich in reserve starch and orange-red coloured oil. Akinetes are formed in
chains of 10 to 40 (Fig. 4). Akinetes germinate directly under favourable conditions.

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(ii) Asexual Reproduction:
i) Asexual reproduction takes place by means of multi-flagellate zoospores produced singly
in intercalary cap cell. Mostly the newly formed cap cell functions as the zoosporangium.
ii) Several factors control zoospore formation of which high pH and CO2 concentration of
medium and a diurnal rhythm of light and darkness are significant.
iii) The zoospores are not formed in chains and one sterile cell is always present between two
zoosporangia.
iv) The cell which functions as zoosporangium gets filled with abundant reserve food and a
slight contraction of the protoplast from the cell wall takes place (Fig. 5 A, B).
v) The central vacuole disappears the chloroplast frees itself from one end of the cell and
becomes conical.
v) The nucleus comes to lie
near this chloroplast. A
small lens shaped hyaline
region is formed between
the wall and the nucleus.
This hyaline bald spot later
forms the anterior end of the
zoospore.
vi) At the base of this
hyaline area a ring of basal
granules appears and from
each basal granule or
blepharoplast a flagellum
arises.
vii) The basal granules are
connected to each other by
fibrous strand. A crown of
about 30 flagella is formed
around the hyaline spot
(Fig. 5 C).
viii) The mature zoospore is
oval, spherical or pear
shaped structure. The
zoospore is uninucleate and
contains a ring shaped
chloroplast. The zoospore is
dark green in colour except
at the hyaline pointed apical
end. A sub apical ring of
flagella is present and such
flagellation is called stephanokontic type (Fig. 5 F).When the zoospore is mature, the wall of
the zoosporangium splits near the apical region and the adjacent cell moves apart to make a
gap for the liberation of zoospore (Fig. 5 D).

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The mucilage substance is secreted at the base of the zoospore which helps in the liberation
of zoospore. The zoospore comes out of the zoosporangium in a delicate mucilaginous
vesicle which soon gets dissolved and the zoospores are liberated in water (Fig. 5 D, E).
Germination of Zoospore:
After liberation, the zoospore swims for about an hour. Then it settles and attaches itself to a
solid substratum with its anterior end downwards. After attachment flagella are withdrawn
and it starts elongation. The lower hyaline part elongates to make holdfast and the upper part
divides repeatedly to make new filament (Fig. 5 G-I).
i) The sexual reproduction in Oedogonium is of advanced oogamous type.
ii) Sexual reproduction is more frequent in still waters than in running water.
iii) The factors influencing sexual reproduction are alkaline medium, deficiency of nutrition,
light and dark periods and increased temperature.
iv) The genus Oedogonium exhibits sexual dimorphism because the male and the female
gametes differ morphologically as well as physiologically. The male gametes are produced in
antheridia and the female gametes are produced in oogonia.
Depending upon the nature of antheridia producing plants, Oedogonium species are of
two types:
(i) Macrandrous:
i) If antheridia are produced on normal size plant, Oedogonium forms are called
macrandrous. Macrandrous species may be monoecious or dioecious.
ii) In monoecious macrandrous species antheridia and oogonia are produced on the same
plant e.g., O. fragile, O. hirnii, O. kurzii and O. nodulosum.
iii) In dioecious macrandrous species antheridia and oogonia are produced on separate male
and female plants of normal size.
(ii) Nannandrous:
i) The female or oogonia bearing plants are normal. The antheridia are produced on special
type of small or dwarf plants, known as Dwarf males or Nannandria.
ii) The dwarf males are formed by androspores which are produced in androsporangia.
If androsporangia and oogonia are formed on same plant, the Oedogonium forms are called
gynandrosporous e.g., O. concatinatum.
iii) If androsporangia and oogonia are formed on different plants, Oedogonium forms are
called idioandrosporous e.g., O. confertum, O. iyengarii and O. setigerum.
iv) According to some algologists, nannondrous species are more primitive.
Antheridia: (i) In Macrandrous forms:
a) The antheridia develop on normal filaments, terminal or intercalary in position.
b) The initial cell which gives rise to antheridia is called antheridial mother cell.
c) It is normally a cap cell. The antheridial mother cell divides by transverse division to form
an upper smaller cell called antheridium and a lower larger cell called sister cell. The sister
cell divides repeatedly to form a row of 2-40 antheridia (Fig. 6 A).
d) Rarely the antheridia are produced singly. The antheridia are broad, flat, short cylindrical,
uninuleate cells. The contents of an antheridial cells divide either longitudinally or
transversely into two.

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The two antherozoids are
positioned side-by-side or
one above the other if
divisions are longitudinal
and transverse respectively.
The antherozoids are
liberated in the same
fashion as zoospores (Fig. 6
B).The liberated
antherozoids or sperm
atozoids or sperms are pale
green or yellow green, oval
or pear shaped.
The antherozoids are motile
about 30 sub-apical flagella
present at the base of beak or hyaline spot (Fig. 6 C). The flagella are sometimes longer than
the body of spermatozoid e.g., in O. crassum and O. kurzii. The antherozoids swim freely in
water before they reach oogonia and take part in fertilization. The antherozoids are similar to
zoospores in structure but these are smaller than zoospores.
(ii) In Nannandrous forms:
i) The antheridia are formed on short or dwarf male plants called dwarf males or nannandria
(Fig. 7 G). The dwarf male filament is produced by the germination of a special type of spore
known as androspore.
ii) The androspore is produced singly within an androsporangium. Androporangia are more
or less similar looking to the antheridia of macrandrous forms and are produced in a similar
manner from a mother cell (Fig. 7 A, B).
iii) The androsporangia are flat, discoid cells slightly larger than antheridia. Each
androsporangium produces a single androspore just as in the case of zoospore. Liberation of
androspore is similar to that of a zoospore.
iv) The androspores look similar to zoospore except for the smaller size. The androspores are
motile and have a subpolar ring of flagella.
v) After swimming about for some time, the androspore settles on oogonial wall e.g., O.
ciliatum or on the supporting cell e.g., O. concatenatum.
vi) The androspore germinates into a dwarf male or nannandrium. Germlings at one celled
stage may divide and produce two antherozoids e.g., O. deplandrum, O. perspicuum (Fig. 7
C-G).
vii) The nannandrium or dwarf male can be a few cells long. It has a basal attaching cell the
stipe and all others cells are antheridial cells.
viii) In many cases cap is present at the top of the apical antheridium. The protoplasm of each
antheridial cell divides to form two sperms or antherozoids which are similar to antherozoids
of macrandrous species.
Oogonia:
i) In Oedogonium the female sex organ oogonia are highly differentiated female gametangia.
These are mostly intercalary but sometimes can be terminal e.g., O. palaiense.
ii) The structure and development of oogonium is identical in macrandrous and nannandrous
species. Like antheridia any freely divided or actively growing cap cell functions as the
oogonial mother cell.

58
iii) The oogonial mother cell divides by
transverse division into two unequal cells, the
upper cell and the lower cell.
iv) The upper larger cell forms oogonium and
the lower smaller cell function as supporting cell
or suffultory cell. In some species the oogonial
mother cells directly forms the oogonium.
Supporting cell is absent is O. americanum.
v) If any of the two divided cells again functions
as oogonial mother cell many oogonia are
formed in chain.
vi) In monoecious species the suffultory cell
may divide to form antheridia. The upper cell
contains more cytoplasm, food and enlarges into
spherical or flask shaped oogonium.
vi) The oogonium also secretes growth
hormones which induce suffultory cell to
increase in size (Fig. 8 A-C).
vii) The protoplast in oogonium
metamorphosis’s into a single egg or oosphere.

59
The oosphere is non-motile, green due to chlorophyll and has a central nucleus.
viii) As the ovum matures, the nucleus moves to periphery, the oosphere retracts slightly
from the oogonial wall and develops a hyaline or receptive spot just outside the nucleus. The
receptive spot receives antherozoids for fertilization.
ix) At receptive spot a pore is formed by gelatinization of wall in proliferous species and a
transverse slit is formed in operculate species.
x) In both species a thin membrane is deposited on the inner node of the exit which functions
as a channel leading down to ovum. In some species a mucilage drop is extruded through
opening to attract antherozoids.
xi) In macrandrous monoecious species, where antheridia and oogonia develop on the same
plant, the Oedogonium species are protogynous i.e., the development of oogonia takes place
before development of antheridia to ensure cross-fertilization.
Fertilization: i) The mature egg secretes chemical substance or mucilage to attract
antherozoids or the antherozoids may enter oogonium through the slit.
ii) The antherozoids swim through the opening of oogonial wall and enter the egg through
hyaline receptive spot (Fig. 8 D-F).
iii) Only one male antherozoid is able to fuse with ovum. After plasmogamy and karyogamy
the male nucleus and female nucleus fuse to form a diploid zygote nucleus.
iv) The zygote secretes a thick wall around itself and forms oospore. The colour of the
oospore changes from green to reddish brown.
v) The oospore is liberated by the disintegration of oogonial wall.
Structure of oospore:
i) The oospore is globular reddish brown structure. The oogonial wall is made of three and
sometimes two layers.
ii) The outermost layer may be smooth in some cases but in most cases it is ornamented with
pits, reticulations, spines, ribs or flanges.
iii) The ornamentation of oospore is of taxonomic importance. The oospore is red in colour
due to accumulation of red oil. Oospore contains a diploid nucleus and cytoplasm rich in
proteins.
Germination of oospore: i) Oospore is a resting spore but sometimes it can germinate
directly. The period of rest for oospore may be a year or more.
ii) According to Mainx (1931) the zygote may require chilling before germination. The
diploid oospore nucleus undergoes zygotic meiosis to form four haploid nuclei before
germination.
iii) The diploid oospore divides to form four haploid daughter protoplasts. Each daughter
protoplast metamorphosis into a zoospore also called as zoomeiospore.
iv) The zoomeiospores are liberated in a vesicle (Fig. 9 A). Soon the vesicle disappears and
as in asexual reproduction the zoospores develop to make Oedogonium plants.
In some cases out of four
nuclei a few may
degenerate forming less
than four zoomeiospores.
In heterothallic forms e.g.,
O. plagiostomum, two
swarmer’s give rise to male
and the two swarmer’s
give rise to female plants.
Under certain conditions
meioaplanospores are
formed instead of zoomeiospores (Fig. 9 B, C).

60
Life Cycle in Oedogonium: In Oedogonium the thallus is haploid and the life cycle is haplontic type. The
diploid stage in life cycle is only zygote. It occurs for a short period. The zygote or oospore undergoes meiosis
to make four meiozoospores which again form haploid Oedogonium thalli. The variations in life cycles of
Oedogonium are due to macrandrous and nannandrous nature of Oedogonium species.
Macrandrous Forms: i) Oedogonium macrandrous species can be monoecious or homothallic, if antheridia
and oogonia are produced on same filament (Fig. 10, 11).
Oedogonium macrandrous species can be dioecious or heterothallic if antheridia are produced on male plants
and oogonia are produced on separate female plants. (Fig. 12).
Nannandrous Forms The nannandrium or dwarf male plants are produced by germination of androspores
which are produced in androsporangia. In gynandrosporous nannandrium forms the androsporangia and oogonia
are formed on same filaments (Fig. 13, 14). In idioandrosporous nannandrium forms, the androsporangia and
oogonia are formed on different plants

61
Chara Life Cycle
Systemic Position: - Kingdom: Plantea,Division: Thallophyta/Charophyta,Subdivision:
Algae, Class: Chlorophyceae/Charophyceae, Order: Charales: Family: Characeae, Genus:
Chara
Occurrence:
i) Chara is fresh water; green alga found submerged in shallow water ponds, tanks, lakes and
slow running water. C. baltica is found growing is brackish water and C. fragilis is found in
hot springs.
ii) Chara is found mostly in hard fresh water, rich in organic matter, calcium and deficient in
oxygen.
iii) Chara plants are often encrusted with calcium carbonate and hence are commonly called
stone wort. Chara often emits disagreeable onion like odour due to presence of sulphur
compounds. C. hatei grows trailing on the soil C. nuda and C. grovesii are found on
mountains, C. wallichii and C. liydropitys are found in plains.
In India Chara is represented by about 30 species of which common Indian species are:
C. zeylanica, C. braunii, C. gracilis, C. hatei and C sgymnoptiy etc.
Thallus Structure of Chara
i) The thallus of Chara is branched, multicellular and macroscopic. The thallus is normally
20-30 cm. in height but often may be up to 90 cm to l m. Some species like C. hatei are small
and may be 2-3 cm. long.
ii) The plants in appearance resemble Equisetum hence Chara is commonly called as aquatic
horsetail. The thallus is mainly differentiated into rhizoids and main axis
Rhizoids:
i) The rhizoids are white, thread like, multicellular, uniseriate and branched structures.
ii) The rhizoids arise from rhizoidal plates which are formed at the base of main axis or from
peripheral cells of lower nodes.
iii) The rhizoids are characterized by presence of oblique septa.
iv)The tips of rhizoids possess minute solid particles which function as statoliths.
v) The rhizoids show apical growth. Rhizoids help in attachment of plant to substratum i.e.,
mud or sand, in absorption of minerals and in vegetative multiplication of plants by forming
bulbils and secondary protonema.
Main Axis:
i) The main axis is erect, long, branched and differentiated into nodes and internodes.
ii) The internode consists of single, much elongated or oblong cell. The inter-nodal cells in
some species may be surrounded by one celled thick layer called cortex and such species are
called as corticate species.
iii) The species in which cortical layer is absent are called ecorticate species.
iv) The node consists of a pair of central small cells surrounded by 6-20 peripheral cells. The
central cells and peripheral cells arise from a single nodal initial cell.
Vegetative structure:
i) The plant is always found attached to the substratum by a well developed rhizoidal system.
The rhizoids are uniseriately branched and obliquely septate. The rhizoids may or may not be
differentiated into nodes and internodes.
ii) The axis has nodes and internodes. Several branches of limited growth also known as
leaves grow in whorls from the nodes of the axis.
iii) These leaves do not grow further after attaining a definite length. The leaves may or may
not be differentiated into nodes and internodes.
iv) They may be branched or simple. This ineternodal cell is sufficiently long and ensheathed
by a cortex of vertically elongated cells.

62
v) The cortex is one celled in thickness and consists of the cells of lesser diameter.
The cell wall: The cell wall consists of homogeneous cellulose. It is not multilayered. Outer
to the cellulose wall there is a gelatinous layer, and this is the sheath for the deposition of
calcium.
The main axis of Chara consists of mainly two types of cells:
(i) Nodal cells (ii) Inter-nodal cells.
i) The nodal cells are smaller in size and isodiametric. The cells are dense cytoplasmic,
uninucleate with few small ellipsoidal chloroplasts.
ii) The central vacuole is not developed instead many small vacuoles may be present.
iii) The cytoplasm can be differentiated in outer exoplasm and inner endoplasm. The inter-
nodal cells are much elongated.
iv) The cytoplasm is present around a large central vacuole. The cells are multinucleate and
contain many discoid chloroplasts.
v) The cytoplasm is also differentiated into outer exoplasm and inner endoplasm. The
endoplasm shows streaming movements.
vi) The cell walls between the nodal cell and inter-nodal cells are porous to help in
cytoplasmic continuity between cells.
Reproduction:
The reproduction takes place by vegetative and sexual methods.
Asexual reproduction is not found.
1. Vegetative reproduction:
The vegetative reproduction takes place by (a) tubers; (b)
amylum stars and (c) secondary protomema.
(a) By tubers and bulbils:
i) The tubers are commonly formed on rhizoids or sometimes even on buried nodes. The
whole structure is full of starch.
ii) Sometimes the globule divides and becomes multicellular and known as ‘simple tuber’.
When the tuber appears on the node, some of the peripheral cells go on dividing and massive
structure is developed. Each starch filled tuber and bulbil may develop into a separate plant.
(b) By amylum or starch stars:
The cells of some subterranean nodes become star-shaped and very much laid in by starch are
called amylum stars. Each such structure develops into new plants.
(c) By secondary protonema: The protonemata like outgrowths come out from a node. Each
such outgrowth is capable to develop into a new plant.

63
2. Sexual reproduction: i) The sexual reproudction is oogamous. A very advanced and
specialized type of oogamy is found. There is a special terminology for the sex organs.
ii) The male fruiting body is called globule and the female nucule. Most of the species are
homothallic (monoecious) and few are heterothallic (dioecious). iii) The globule is borne on
secondary lateral of limited growth. iv) One globule and one nucule bome on one node of the
leaf. v) In homothallic species both the fructifications borne on the same node. In Chara the
nucule is borne above the globule.
Development of globule:
i) A single superficial nodal
cell of the adaxial side of
the leaf acts as the initial of
both the fructifications, i.e.,
nucule and globule.
ii) This superficial cell
divides into two derivatives
by a transverse wall. One
cell derivative of the
superficial cell is the initial
cell of the globule and the
other is the initial cell of
the nucule.
iii) The globule initial cell
divides transversely and
two daughter cells are
formed. The lower daughter cell does not divide further and converts into the pedicel cell.
iv) The upper daughter cell divides twice successively and four cells are formed arranged in
quadrants.
v) Each of these quadrants divides transversely and eight cells are produced thus attaining
octant stage. Each of these eight cells divides periclinally and thus produced eight outer cells
which divide further periclinaily.
vi) The outermost eight cells are called shield cells. The middle cells are known as manubrial
cells and the innermost eight cells are primary capitulum cells. The shield cells become very
much enlarged and expanded.
vii) The manubrial cells become very much radially elongated, but the primary capitulum
cells are arranged compactly to each other in the centre of the globule.
viii) The outer walls of the shield cells fold inward and the shield cells appear multicellular
structures.
ix) The infoldings are incomplete. The shield cells develop red pigments in them and so the
globules appear orange red in colour from each primary capitulum cell six secondary
capitulum cells are cut off inside the globule.
x) These secondary capitulum cells rarely develop tertiary cells. On the secondary capitulum
cells the initials of antheridial filaments are produced. These initials may also be produced
upon primary or even tertiary capitulum cells.
xi) Each antheridial initial develops into a branched or unbranched antheridial filament. Each
antheridial filament has many compartments or cells in it. Each cell is supposed to be an
antheridium.
x) The protoplast of each antheridium metamorphoses into a single antherozoid. The
antherozoid is elongated, coiled and biflagellate. The flagella are sub-terminal in origin.

64
The nucleus is elongated and coiled.
Some unused cytoplasm is found in the
tail of the antherozoid.
xi) On the maturity of the antherozoids
the shield cells of the globule somewhat
separate from each other, the antheridial
filaments protrude out through these
openings and the antherozoids liberate in
the water. The liberation of antherozoids
usually takes place in the morning.
Development of nucule:
i) The nucule develops from the adaxial
cell of basal node of the globule.
ii) The globule is homologous with the
branch of limited growth and the nucule
with the branch of unlimited growth.
iii) The nucule initial divides twice and a
row of three cells is formed. The
terminal cell acts as oogonial mother
cell which elongates sufficiently in

65
vertical direction and transverse wall develops in the lower region of it dividing it into two
cells. The lower small cell and the upper one is oogonium which contains an egg.
iv) The lowermost cell of the row of three cells does not divide and acts as a pedicel.
v) The middle cell divides vertically in such a way so that a single central cell and five sheath
initials are produced.
vi) The sheath initials surround the central cell. The sheath initials elongate vertically
sometimes even before the vertical elongation of the oogonial mother cell and encircle it.
vii) Each of the sheath initials divides transversely forming the upper tier of coronary cells
and lower tier of tube cells.
viii) The tube cells elongate several times to their original length and become spirally coiled
around the oogonium. The coronary cells do not elongate much and act collectively as the
corona of the nucule.
Fertilization:
i) Prior to fertilization the elongated and
twisted tube cells become separated from
each other and five small slits are
developed just below the corona.
ii) The swimming antherozoids around the
nucule try to enter through these openings.
iii) The flagella are withdrawn and one of
the antherozoids penetrates the egg. The
male nucleus travels downwards and fuses
with the egg nucleus developing a diploid
(2n) nucleus. This diploid nucleus situates
in the bottom of the zygote. The zygote
settles down in the mud, secretes a thick
wall and germinates on the approach of
favourable conditions.
The zygote and its germination:
i) In favourable conditions the zygote
germinates. The diploid (2n) nucleus
moves to the top of the zygote and divides
meiotically producing four halpoid nuclei.
ii) Simultaneously a septum divides the
zygote into two unequal cells. The small
distal cell is lenticular cell and contains
one functional nucleus in it.
iii) The remaining big cell is called
storage cell; possessing three nuclei in it
disintegrate very soon. The outer wall of
the ornamented zygote cracks and the
lenticular cell exposes. iv) The lenticular
cell divides by a vertical wall giving rise
to a protonematal initial and a rhizoidal
initial.
v) The protonematal initial develops into a
primary protonema which later on differentiates into nodes and internodes. The rhizoidal
initial gives rise to a colourless rhizoid having nodes and internodes.From the lowermost
node of the protonema the appendages are given out which develop into secondary
protonema or rhizoids. From the second node of the protonema a whorl of appendages is

66
given out. All the appendages except one develop into green filaments. The life cycle is of
Haplontic type. All phases but zygote are haploid.
Advanced features of the Charales:
i) The position of the Charales is controversial on account of the multicellular female organ,
the complex antheridium, strong apical growth by vegetative shoots and a degree of
specialization which is generally not found in other green algae.
ii) The female sex organ possesses a sterile jacket of cells, which is not found in the typical
oogonium of other green algae. In 1875, Sachs referred the oogonium of Chara as a nucule.
iii) The presence of sterile jacket of cells is a new thing for the algae whereas on the other
hand it is characteristic of the archegonium in the Embryophyta. But the jackets of these two
groups are not supposed to be homologous.
iv) A parallel or analogous situation is found in the Rhodophyceae, where the female organ is
a fairly complex structure.
v) In the same way the antheridium of the Charales is a much more complex structure than
the typical antheridia and does not resemble the antheridia of either Bryophyta or
Tracheophyta. Sachs (1875) called the antheridium as a globule.
___________________________________________________________________________
The main characteristics of phaeophyceae are:
1. The algae of this family are commonly known asbrown algae.
2. The members of phaeophyceae are mostlymarine.
3. Most of them are large sized and multicellular;simple forms are absent.
4. In addition to the golden brown carotene pigmentit also possesses chlorophyll a,
chlorophyll c.
5. The reserve food material is present as Laminarin and Mannitol.
6. It possesses double layered cell wall; the inner layer of cellulose and outer layer of
phycocolloids and fucoxanthin.
7. Many of the cells possess a characteristic fucosan vesicle.
8. The plant body is attached to the substratum by ahold fast, has a stalk, a stipe and leaf
like photosynthetic part.
9. Reproduction occurs both by asexual and sexual methods.
10. Asexual reproduction occurs by fragmentation, zoospores and aplanospores.
11. Sexual reproduction takes place by isogamy, anisogamy or oogamy.
12. The large brown algae are called trees of seas or Kelps.
Life Cycle of Ectocarpus
Systematic Position: Class: Phaeophyceae Order: Ectocarpales Family: Ectocarpaceae
Genus: Ectocarpus
Occurrence
i) Ectocarpus is a brown alga. It is abundantly found throughout the world in cold waters. A
few species occur in fresh waters. ii) The plant grows attached to rocks and stones along
coasts. Some species are epiphytes on other algae like members of Fucales and
Laminaria. Ectocarpus fasciculatus grows on the fins of certain fish in Sweden. iii)
Ectecarpus dermonemcnis is endophytic. Ectocarpus carver and Ectocarpus spongiosus are
free- floating.
Vegetative Structure Structure of thallus:
i) Genetically the thalli may be haploid or diploid. But both the types are morphologically
alike. The thallus consists of profusely branched uniseriate filaments.
ii) It shows heterotrichous habit. There are two systems of filaments. These are prostrate and
projecting system. The filaments of the projecting system arise from the filaments of prostrate
system

67
a) Prostate system: i) The prostrate system consist of creeping, leptate, irregularly branched
filaments.
ii) These filaments are attached to the substratum with the help of rhizoids. This
system penetrates the host tissues in epiphytic conditions.
iii) Prostrate system is poorly developed in free floating species.
b) Projecting system: i) The projecting system arises from the prostrate system. It consists
of well branched filaments. ii) Each branch arises beneath the septa. The main axis and the
branches of the projecting system are uniseriate. iii) In this case, rens are joined end to end in
a single series. iv) The branches terminate into an acute point to form a hair. v) In some
species the older portions of main axis are ensheathed (corticated). This sheath is formed of
a layer of descending rhizoidal branches.
Cell Structure
The cells are small. They are cylindrical or rectangular and uninucleate.
i) The cell wall is thick It is composed of three layers composed of pectic-cellulose. Algin
and fucoidan are also present in the cell wall.

68
ii) These are characteristic gelatinous substances of tne walls of brown algae.
iii) The chromatophores may ribbon-like with irregular outline or disc- shaped.
iv) The dominant of Ectocarpus is fucoxanthin.
v) It gives this algae golden brown colour. vi) The other photosynthetic Pigments are
chlorophyll-a,-c, beta.carotene and other xanthophylls.
vii) Pyrenoid-like bodies-are associated with the chromatophores
viii) All other eukaryotic organelle are present
ix) Intercalary: In some species, an intercalary meristem ir present it the base of the hair. It
is called trichothallic meristem
x) it increases the length of the terminal hair and vegetative cell of the branch. This growth is
called trichothallic growth. The growth in the prostrate system is apical
Reproduction
Ectocarpus reproduces by both asexual and sexual methods.
Asexual reproduction
i) The asexual reproduction takes place by the formation of biflagellate zoospores. ii) These
zoospores may be haploid produced in one-celled Unilocular Sporangia. Or they may be
diploid formed in many celled Plurilocular Sporangia. iii) Both kinds of sporangia are
present on the same diploid sporophyte plant. iv) The sporangia are borne terminally and
singly on lateral branches.
(a) Unilocular Sporangia
i) A unilocular sporangium develops from a terminal cell of a short lateral branch.
ii) The sporangial initial enlarges in size. It becomes globose or ellipsoidal.
iii) The number of chromatophores also increases in it. The nucleus of the sporangium
divides meiotically to produce four haploid nuclei.
iv) These nuclei undergo repeated mitotic divisions to produce 32-64 daughter nuclei.
v) A small amount of cytoplasm surrounds a nucleus and a chromatophore to produce
daughter protoplasts.
vi) Each daughter protoplast metamorphoses into a meiozoospore (produced by meiosis).
Meiozoospore is pyriforrn and biflagellate.
vii) The flagella are laterally inserted and are of unequal size. The larger one directed forward
and the smaller one is directed backward. An apical pore is formed in the gelatinous mass of
sporangia. The meiozoospores come out of this pore.
viii) These are separated from each other after few moments. They swim freely in all
directions. A new sporangium may be nroduced within the old sporangial wall after the
liberation of zoospores.
(b) Plurilocular
Sporangia
i) The plurilocular
sporangia are stalked or
sessile. These are
elongated, cone-like
multicellular structures.
ii) These also develop
from a terminal cell of a
short lateral branch. The
sporangial initial enlarges
in size.
iii) It undergoes repeated
transverse mitotic
divisions. It produces a

69
vertical row of 6-12: cells. iv) These cells then divide by vertical and transverse divisions
repeatedly. They form a cone-like structure. v) This cone consists of hundreds of small
cubical cells. These cells are arranged in 20-40 transverse tiers. Each cell represents a
sporangium. vi) The protoplast of each cell metamorphoses into
single mitozoospore (produced by mitosis).
vii) The mitozoospore is pear-shaped, diploid and biflagellate. The flagella are of unequal
size they are laterally
inserted.
viii) The mitozoospores are
liberated through a terminal
or a lateral pore. This pore is
formed in the wall of the
sporangium.
Germination of Zoospores
a) Germination of
meioszoospores: i) The
zoospores formed in
unilocular sporangia
(meioszoospores) swarm for
same time.
ii) They then come to rest on
some solid object. They
withdraw their flagella and
secrete a membrane around
then.
iii) They germinate and form a small germ tube. This tube is separated prom the
meiozoospore cell through a septum. This germ tube divides and redivides.
iv) It forms the prostrate system of plant. The projecting system arises from the filaments of
the prostrate system.
v) The new plant form is haploid. Therefore, it is gametophyte.
vi) The meiozoospores develop into a gameiophytic olant. Therefore, these spores are also
called as gonozoospores.
b) Germination of mitozoospores: The zoospores proauced in olurilocular sporangia are
mitozoospores. They develop in the same manner as the meiozoospores. But they are diploid.
Therefore, they develop into a diploid sporophyte. Therefore, the mitozoospores are also
called as neutral spores.
Sexual Reproduction
i) Sexual reproduction takes place by isogamy or anisogamy. Majority of the species are
isogamous and homothallic.
ii) Some species are anisogamous. Ectocarpus secundus is heterothallic and anisogamous. iii)
The gametes are produced in Plurilocular gametangia. These gametangia are many-celled,
elongated, and sessile or shortly stalked structures.
iv) These gametangia are produced on the haploid plants developing from the meiozoospores.
The development of gametangia is similar to that of plurilocular sporangia.
v) These develop from terminal cell of a lateral branch. The gametangial initial gets inflated.
It divides mitotically by repeated transverse divisions. It produces a vertical row of flat cells.
vi) These cells undergo repeated vertical and transverse divisions. They form many hundred
small cubical cells.
vii) These cells are arranged in 24-40 transverse rows. viii) The protoplast of each cell
metatnorphoses into a single, pyriform, biflagellate, haploid zoogamete.

70
ix) The flagella are laterally attached. The zoospores and the gametes are similar in structure.
But the gametes are relatively smaller in size. x) The gametes are liberated from the
gametangium an apical pore formed in the cell of the sporangium.
Forms of sexual reproductions
1. Isogamy: Isogamous species are E. pusilus and E. globifer etc. In these species, the fusion
takes place between alike gametes. These gametes belong to the same plant or even to toe
same gametangium.
2. Physiological anisogamy or Clump Formation:
i) It occurs in species like E. siliculosis. The fusing gametes are identical morphologically.
But they show different sexual behaviour. ii) One is less active and is called female gamete.
iii) The other is more active and is called male gamete. The female gamete soon comes to
rest. It settles on a substratum. It becomes surrounded by active male gametes. iv) The male
gametes attach themselves to the female gamete through their anterior flagella. The anchoring
flagellum contracts. v) Therefore, the body of the male gamete comes in contact with that of
the female gamete and the fusion takes place. This phenomenon is called clump formation.
3. Morphological Anisogamy: It occurs in species like E. secundus. In this case, the two
fusing gametes are dissimilar in size. They are produced in different gametangia: The smaller
ones are produced in microgametangia. The larger ones are produced in megagametangia
Fertilization
Ferelization occurs and
diploid zygote is formed.
There is no zygotic meiosis.
The zygote germinates into a
diploid sporophyte.
Alternation of Generations
Ectocarpus shows
isomorphic alternation of
generations.
a) Sporophyte: i) The
sporophyte is diploid. It
develops two types of
sporangia. Zoospores are
produced in these sporangia.
ii) Zoospores are produced
by mitosis (mitozoospores) in
plurilocular sporangia.
iii) The zoospores in
unilocular sporangia are
produced meiotically
(meiozoospores).
The mitozoospores
germinate into a diploid
sporophyte.
iv) These spores cause
reduplication of sporophyte
generation. The
meiozoospores germinate to
give rise a haploid gametophyte plant.
Gametophyte: i) It develops plurilocular gametangia. These gametophytes are similar to the
sporophyte in morphology.

71
ii) Haploid gametes are produced in the gametangia. These gametes fuse to form a diploid
zygote.
iii) Zygote germinates into a diploid sporophyte plant. In some species the gametophyte
generation is also reduplicated by the parthenogenesis. In this case, the gametes from
plurilocular sporangia form new gametophyte generation.
Occurrence of Polysiphonia:
i) Polysiphonia is a large genus with
about 200 species. ii) The genus is
represented in India by about 16 species
found is southern and western coasts of
India. Some common Indian species are
P. ferulacea, P. urceolata and P.
variegata.
iii) Most of the species are lithophytes

72
i.e., found growing on rocks. Some species are epiphytic, found growing on other plants and
algae e.g., P. ferulacea grows on Gelidium pusillum. P. variegata grows on the roots of
mangroves.
iv) Some species are semi parasitic e.g., P. fastigiata
is semiparasiite on Ascophyllum nodosum and Fucus.
Thallus Structure of Polysiphonia:
i) The thallus is filamentous, red or purple red in
colour. The thallus is multi-axial and all cells are
connected by pit connections hence, the name given
is Polysiphonia. Due to continuous branching and re-
branching the thallus has feathery appearance.
ii) The thalli may reach the length of about 30 cm.
The thallus is heterotrichous and is differentiated into
a basal prostrate system and erect aerial system.
iii) The prostrate system creeps over the substratum.
Its functions are attachment of the thallus to the
substratum and perennation. In many species of
Polysiphonia e.g., in P. nigrescens, the prostrate
system is well developed and multi-axial in structure.
iv) In some species e.g., in P. elongata and P.
violacea the multi-axial prostrate system is absent.
The plants remain attached to the substratum by:
(a) Unicellular richly branched hizoids arising from
multi-axial prostrate system.
(b) Rhizoids arising from the erect system, forming,
an attachment disc or hapteron.
(c) By the unicellular rhizoids arising in groups from the prostrate system e.g., P. fastgata.
i) The erect aerial system arises from the prostrate system. It is made of multi-axial branched
filaments. ii) The main axis and long branches have similar structure. iii) These are made of a
central large filament or central siphon of cylindrical cells. iv) The central siphon is
surrounded by a number of pericentral
cells or pericentral siphons. The number
of pericentral siphons varies from
species to species. v) The length of
central and pericentral siphons is equal
hence, the filaments appear to be divided
in nodes and internodes like. vi) Each
pericentral siphon remains connected
with central siphons through pit
connections. v) The successive central
siphon cells and all peripheral cells are
also connected to each other through pit
connections. Hence the complete thallus
makes a polysiphonaceous structure
(Fig. 2 C).
Branching:
The thallus of Polysiphonia bears two types of branches (a) Short branches (b) Long
branches. The branches are lateral and monopodial. The branching starts from the cell lying
2-5 cells below the apical cell.

73
(A) Short Branches or Trichoblasts:
The short branches or trichoblasts are branches
of limited growth. These are uniaxial in
structure and lack pericentral siphons. The cells
are connected to each other by pit connections.
These branches arise on main axis and on long
branches in spiral manner. Their cells contain
very few chromatophores.
These branches are deciduous, perennial species
shed these branches before winter and develop
again in spring season. The basal cell of the last
trichoblast is retained as scar cell by the
pericentral siphon.
Development of Trichoblast:
The trichoblast initial is differentiated from a
cell 2-5 cells below the apical cell (Fig. 3 A, B).
It starts as a small cell and divides repeatedly to form dichotomously branched, uniseriate
multicellular hair like trichoblast (Fig. 4 C, D). The trichoblast may bear male and female
reproductive structures or remain sterile.
(B) Long Lateral Branches:
The long lateral branches are branches of unlimited growth are polysiphonous at the base and
monosiphonous in terminal parts. These branches develop from the basal cells of short
branches. In species like P. violacea they develop as outgrowth from trichoblast initial. They
develop along with trichoblast and after few divisions the trichoblasts are pushed aside so
they appear to arise from trichoblast dichotomously.
The outgrowth functions as the apical cell of the Long Branch which after repeated division
forms the central siphon. The central siphon later on develops pericentral siphons. In species
like P. elongata the long branches arise directly from the main axis. The outgrowth develops
from a cell 2-5 cells below the apical cell. The outgrowth forms central siphon and later
pericentral siphon in normal way.
Cell Structure of Polysiphonia:
i) The cells of central and pericentral siphons are cylindrical and elongated. The cell wall is
differentiated into outer pectic and inner cellulosic layer.
ii) The cell contains a large central vacuole which is delimited by a membrane tonoplast. The
cytoplasm is present between the cell wall and the central vacuole.
iii) The cell contains a number of red discoid chromatophores which lack pyrenoids. The
chromatophores contain pigments chlorophyll a, chlorophyll d, a carotene, (3 carotene, r-
phycoerythrin and r-phycocyanin.
iv) The chromatophores are parietal in position (Fig. 2A). The central siphon cells and
pericentral siphon cells posses’ single peripheral nucleus. The cytoplasm contains granules of
floridean starch as food reserve.
Growth of Polysiphonia: The growth takes place by the dome shaped apical cell located on
the tip of central siphon. The apical cell cuts many cells on lower side by transverse divisions
which form the central siphon. Some of the lower cells divide vertically to form pericentral
cells.
Reproduction in Polysiphonia:
Polysiphonia is mainly heterothallic. In the life cycle of Polysiphonia three kinds of
thalli are found. These are:

74
(a) The gametophytic thalli which are haploid free living and dioecious. The male sex organs
spermatangia are formed on male
gametophytic plant and the female sex
organs carpogonia are formed on
female gametophytic plant.
(b) The carposporophytes are diploid,
depend upon the female gametophyte.
They develop after fertilization from
zygote and later bear carposporangia.
The carposporangia form diploid
carpospores.
(c) The tetrasporophytic plant which is
formed by germination of diploid
carpospores is diploid and
independent. Then plant bears
tetrasporangia which form four
haploid tetraspores which again give
rise to male and female gametophytic
plants.
In life cycle of Polysiphonia both
asexual and sexual reproduction takes
place. The life cycle is example of
triphasic alternation of generation.
Sexual reproduction is oogamous type and plants are dioecious i.e., male and female sex
organs are produced on different male and female gametophytic plants.
Male Gametophyte:
i) The male sex organs,
spermatangia or antheridia develop
on fertile trichoblasts present on tips
of male gametophytic plant.
ii) The male trichoblast when only
2-3 celled divides dichotomously. In
most of the species one branch
remains sterile and the other bears
spermatangia, in some specie both
branches become fertile.
iii) The sterile branch may divide
again to form fertile trichoblasts.
The cells of fertile uniaxial
trichoblast except the 2-3 divide
periclinally to form pericentral cells.
iv) The pericentral cells form
spermatangial mother cells on outer-
side (Fig. 4B). Each spermatangial
mother cell cuts off 2-4 sporangia on
outer side. The complete structure
makes cone shaped cluster of
spermatangia (Fig. 4 A).
v)The mature spermatangium is a globular or oblong, unicellular structure.

75
vi) Its cell wall is differentiated into three layers, inner refractive middle, gelatinous and outer
thick layer. vii)The uninucleate protoplast of spermatagnium forms a male gamete or
spermatium. The spermatium is non-motile and is released through an apical pore in the
spermatangium (Fig. 4 C).
Female Gametophyte:
i) The female sex organ of Polysiphonia is called as carpogonium. (Fig. 5 F).
ii) The carpogonium develops on trichoblast on female gametophytic plant.
iii) The trichoblast initial arises from a cell, 2-4 cells behind the apical cell.
iv) It develops into 5-7 celled female trichoblast. The three lower cells form 5 pericentral
cells of which there is one adaxial, two lateral and two abaxial cells (Fig. 5 C-E).
v) These cells surround the central cell. The adaxial cell called supporting cell, forms a basal
sterile filament initial, a lateral sterile filament initial and a curved four celled carpogonial
branch.
vi) The basal swollen flask shaped cell of the carpogonial branch functions as carpogonium
or egg cell and the upper tubular elongated part is called trichogyne (Fig. 5 C).
vii) The lateral sterile filament initial divides to form two celled lateral sterile filament. The
pericentral cells surrounding carpogonium form outgrowths to cover the carpogonium. The
sterile sheath around carpogonium is called pericarp (Fig. 5 F).
Fertilization:
i) The spermatia are carried to the
trichogyne of carpogonium through
water currents. The spermatium
adheres to the trichogyne by the
mucilage around it.
ii) The walls between spermatium and
the trichogyne dissolve. The male
protoplasm enters carpogonium
through trichogyne. After fertilization
of male and female nuclei, a diploid
zygote cell is formed.
Post fertilization changes:
i) After fertilization many changes
take place within and around the
female reproductive structure.
ii) The basal sterile initial divides to
form basal sterile filaments which are
2-4 celled. The lateral sterile initials
divide to make lateral sterile filaments
which are 4- 10 celled.
The sterile filaments are of nutritive
nature.
iii) The supporting cell divides
transversely to form an auxiliary cell
between itself and the carpogonium. A
tubular protoplasmic connection is
established between auxiliary cell and
carpogonium (Fig. 6A, B).
iv) The diploid zygote nucleus divides
mitotically and forms two diploid

76
nuclei of which one nucleus remains in the carpogonium and the other nucleus migrates into
the auxiliary cell.
v) The auxiliary eel which contains one haploid nucleus receives this diploid nucleus.
vi) The haploid nucleus of the auxiliary cell degenerates and it then contains diploid nucleus
only.
vii) The trichogyne at this time degenerates, the carpogonium, auxiliary cell and supporting
cell fuse and form irregular shaped placental cell.
viii) The diploid nucleus of the auxiliary cells divides mitotically forming many diploid
nuclei in the placental cell.
ix) A number of gonimoblast initials arise from the placental cell and each initial receives a
diploid nucleus from placental cell. Each gonimobalst initial forms a two celled gonimoblast
filament or gonimalobe.
x) The lower cell of gonimoblast filament can also give rise to new gonimoblast filaments.
All the gonimoblast filaments make a compact mass and this structure arising from diploid
zygote cell is V called the carposporophyte (Fig. 6 B-D).
Carposporophyte:
i) This is diploid sporophytic
phase in life cycle of
Polysiphonia and it is
dependent upon the
gametophytic haploid phase.
ii) The carposporophyte or
cystocarp or gonimocarp is
made of many gonimoblast
filaments attached on the
placental cell which remain
covered by Sterile pericarp.
(Fig. 6 B-D).
iii) It is urn shaped structure.
The terminal cell of the
gonimoblast filament
Carpogonium develops into a
carposporangium which forms
a single diploid carpospore.
iv) The diploid carpospores
are liberated through the
ostiole of carposporophyte
(Fig. 6E-F). The catpospores are carried away by water and germinate on suitable substratum.
The carpospore develops a wall around itself and then divides by mitotic division to make a
small lower cell and the larger apical cell. The two celled filament divides to make four
celled filament.
v) The lowermost cell of the filament differentiates into rhizoidal cell and the uppermost cell
makes the apical cell. The apical cell divides transversely to make central siphon cell which
divide periclinally to make pericentral cells. The germination of diploid carpospore results in
the formation of diploid tetrasporophytic plant (Fig. 6G-I).
Tetra sporophyte:
i) The tetra sporophytes are free living diploid plants in the life cycle of Polysiphonia.
ii) Morphologically these plants are similar to haploid gametophytic plants but they do not
bear male or female sex organs like gametophytic plants.

77
iii) Some pericentral cells of tetrasporophytic plant function as tetra sporangial initials. These
are smaller than other pericentral cells and only one in each tier.
iv) The tetra sporangial initial divides by vertical division to make an outer cover cell (Fig. 7
A-C) and the inner sporangial mother cell. The cover cell divides further to make two or
more cover cells.
v) The sporangial mother cell divides by transverse division to make a lower stalk cell and
the upper sporangial cell.
vi) The sporangial cell enlarges and makes tetra sporangium. The branches bearing tetra
sporangia become twisted and swollen and are called stichidia.
vii) The diploid nucleus of tetra sporangium divides meiotically forming four haploid nuclei
followed by the division of protoplast. The four uninucleate segments develop into four
haploid tetra spores or meiospores which are arranged tetrahedrally.
viii) The tetra spores on maturity are liberated by splitting of sporangial wall accompanied by
lifting of the cover cell. Two of the four tetra spores germinate to make haploid male
gametophytic plant and the two make haploid female gametophytic plants (Fig. 7 D-I). Hence
the asexual reproduction in Polysiphonia take place by means of haploid tetra spores which
are formed on tetrasporophytic plant.
Alternation of Generation:
The life cycle of Polysiphonia
exhibits triphasic alternation of
generation. In the life cycle three
distinct phases occur.
These are:
1. Gametophytic phase.
2. Carposporophyte phase.
3. Tetra sporophyte phase.
i) Polysiphonia is dioecious plant.
The male gametophytic plants and
the female gametophytic plants are
distinct.
ii) The haploid male gametophytic
plant bears sex organs spermatangia
which produce haploid spermatia.
iii)The haploid female gametophytic
plant bears sex organs carpogonium.
iv) The fertilization takes place in
situ and diploid zygote nucleus is
formed.
v) The zygote develops in second
phase of life cycle, the
carposporophyte is dependent upon
female gametophytic plant.
vi) The carporophyte is um shaped
structure and forms diploid carpospores in carposporangia.
vii) The carpospores germinate to make diploid tetrasporophytic plants. The tetrasporophytic
plant bear tetra sporangia.
viii) The diploid tetra sporangial nucleus divides meiotically to form four haploid tetra spores
which again make gametophytic male and female plants.

78
ix) In life cycle of Polysiphonia two diploid phases carposprophyte and tetra sporophyte
alternate with one haploid gametophytic phase. The life cycle of Polysiphonia can be called
as triphasic diplobiontic with isomorphic alternation of generation (Figs. 8, 9).
9. Economic importance of algae in Agriculture and Industry.
Economic Importance of Algae
Recent estimates show that nearly half the world’s productivity that is carbon fixation, comes from
the oceans. This is contributed by the algae, the only vegetation in the sea. Algae are vital as primary
producers being at the start of most of aquatic food chains.
Algae as Food: Algae are important as a source of food for human beings, domestic animals and
fishes. Species of Porphyra are eaten in Japan, England and USA. Ulva, Laminaria, Sargassum and
Chlorella are also used as food in several countries. Sea weeds (Laminaria, Fucus, Ascophyllum) are
used as fodder for domestic animals.
Algae in Agriculture:
i) Various blue green algae such as Oscillatoria, Anabaena, Nostoc, Aulosira increase the soil
fertility by fixing the atmospheric nitrogen.
ii) In view of the increasing energy demands and rising costs of chemically making nitrogenous
fertilizers, much attention is now being given to nitrogen fixing bacteria and blue green algae.

79
iii) Many species of sea weeds are used as fertilizers in China and Japan.
Algae in Industry
a. Agar – agar: This substance is used as a culture medium while growing bacteria and fungi in the
laboratory. It is also used in the preparations of some medicines and cosmetics. It is obtained from the
red algae Gelidium and Gracillaria.
b. A phycocolloid Alginic acid is obtained from brown algae. Algin is used as emulisifier in ice
creams, tooth pastes and cosmetics.
c. Idodine: It is obtained from kelps (brown algae) especially from speicies of Laminaria.
d. Diatomite: It is a rock-like deposit formed on the siliceous walls of diatoms (algae of
Chrysophyceae). When they die they sediment, so that on the seabed and lake bottom extensive
deposits can be built up over long periods of time. The resulting ‘diatomaceous earth’ has a high
proportion of silica. Diatomite is used as a fire proof material and also as an absorbent. It is used in
sound and fire proof rooms. It is also used in packing of corrosive materials and also in the
manufacture of dynamite.
Algae in space travel: Chlorella pyrenoidosa is used in space travel to get rid of Co2 and other body
wastes. The algae multiply rapidly and utilize the Co2 and liberate 02 during photosynthesis. It
decomposes human urine and faeces to get N2 for protein synthesis.
Single cell protein (SCP): Chlorella and Spirulina which are unicellular algae are rich in protein and
they are used as protein source. Besides, Chlorella is a source of vitamin also. The rich protein and
aminoacid content of chlorella and Spirullina make them ideal for single cell protein production. An
antibiotic Chlorellin is extracted from Chlorella.
Sewage Disposal:Algae like Chlorella are grown in large shallow tanks, containing sewage. These
algae produce abundant oxygen by rapid photosynthesis. Microorganisms like aerobic bacteria use
these oxygen and decompose the organic matter and thus the sewage gets purified.
Harmful effects of Algae
i) Under certain conditions algae produce ‘blooms’, that is dense masses of material.
ii) This is especially true in relatively warm conditions when there is high nutrient availability, which
sometimes is induced by man as and when sewage is added to water or inorganic fertilizers run off
from agricultural land into rivers and lakes.
iii) As a result of this a sudden and explosive growth of these primary producers (algae) occurs. They
are produced in such a huge quantity that they die before being eaten.
iv) The process of decomposition is carried out by aerobic bacteria which in turn multiply rapidly and
deplete the water of oxygen.
v) The lack of oxygen leads to the death of fish and other animals and plants in the lakes.
vi) The increase of nutrients which starts off the entire process is called eutrophication and if rapid it
constitutes a major problem of pollution.
vii) The toxins produced by algal bloom can also lead to mortality.
viii) This can be a serious problem in lakes and oceans. Sometimes the toxins may be stored by
shellfish feeding on the algae and be passed on to man causing the disease called paralytic shellfish
poisoning.
ix) Algae also cause problems in water storage reservoirs where they may taint the water and block
the beds of sand used as filters.

3. iii unit cbcs

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