Anthoceros

DEPARTMENT OF BOTANY
KIRORI MAL COLLEGE
ASSIGNMENT
TOPIC: REPRODUCTION IN
ANTHROCEROS AND EVOLUTIONARY
TRENDS IN ANTHROCEROS
Submitted by: Swati singh
Submitted To: Dr.Sunil Dhiman Sir
Roll no: 1934127
Subject: Archegoniate
Course: B.Sc Botany Honours 2nd
semester

INTRODUCTION
Anthoceros, with about 200 species is cosmopolitan but occurs
mainly in temperate and tropical region. About 25 species
recorded from India
The thallus is irregularly shaped, not bilaterally symmetrical (as is
common with hornworts), compressed, dark green, and has a
smooth surface.
CLASSIFICATION

REPRODUCTION
Anthoceros reproduce by Vegetative and Sexual Reproduction.
It may be monoecious (A.fusiformis, A.himalayensis) or
dioceous(A.erectus, A.laevis)
VEGETATIVE PROPAGATION
(a) By Progressive Death and Decay of the Older
Parts of the Thallus fragmentation
As in Riccia and Marchantia , the growth of apical
region of thallus and the progressive death of the older
posterior part results in new plants. It takes place by the
decay of the older basal parts of the thallus and by
continuous growth from the growing point. Each
separated lobe by continuos apical growth grows into
new thallus
(b) By Gemmae:
Gemmae are known to develop on the dorsal surface of the thallus
in some species of Anthoceros (A. gladulosus, A. formosii, A.
propaguliferous). They are stalked and often develop mucilage

pores. On separation from the parent plant, the detached
Gemmae grow into a new gametophyte.
(c)Tubers
Under unfavorable conditions, some thallus forms tubers. These
tubers are rich in stored fats and proteins. These tubers germinate
to on the margin of the lobes. They can survive long periods of
drought. Tuber detach and from new plants.
In A.laevisb , the tubers develop as swelling behind one of
more of the growing points persisting along the sides.
In A.pearsoni the tubers are formed along the margin.
In A.himalayensis the tubers are usually stalked and arise from
the ventral surface or from the margins of sterile plants.

(d)Apospory
Schwarbencbach and Lang reportedthat Anthoceros thallus
arise from the unspecialized cells of various part of
sporogonium particularly the intercalary meristem zone,sub
epidermal zone and sporogenous regions of the capsule.
SEXUAL REPRODUCTION IN ANTHOCEROS
Anthoceros is either dioecious i.e., hetero- thallic (e.g.,
A. himalayensis, A. hallii, A erectus, A. pearsoni) or
monoecious i.e., homothallic (e.g., A. fusiformis, A.
gollani, A. punctatus). Monoecious species are usually
protandrous i.e., antheridia mature before archegonia.
Antheridia and archegonia are embedded in the dorsal

surface of the thallus. They develop in continuous rows
just behind the apical growing point.
Antheridia
 The antheridia are present on the upper side of the thallus in
small cavities.
 They are found in groups of 2-4.
 The antheridia cavities are completely covered by a double
layer of cells.
 They have no opening to the outside.
 Each antheridium is borne on a multicellular stalk.
 The main body of the antheridium is globose
 . It has a single celled thick jacket.
 Antheridia have mass of androgonial cells.
 They give rise to biflagellate antherozoids
DEVELOPMENT OF ANTHERIDIUM

ANTHERIDIUM AFTER MATURATION
It has club shaped or pouch like body borne upon a stalk .
The stalk may be slender and composed of four rows of
cells.as in A.puctatus and A.erectus .
On maturity of antheridia, the roof of antheridial wall chamber
ruptures exposing thereby the antheridia. Then after absorbing
water the antheridial wall cracks ruptures by apical aperture.
As a result sperms are liberated to the surrounding film of water.

ANTHEROZOIDS
Bagchee (1924) found that the antherozoid of A.laevis has a
linear body
 The antherozoids is spindle like and biciliate.
 The cilia are attached to the anterior end of the body.
 Sometimes just near the attaching point of the flagella to the
body, the blepharoplasty
(flagellated cell or basal body) is visible.
 The antherozoids swim in the water by the lashing moment
of their flagella.
 At maturity, the roof of the antheridial chamber ruptures,
exposing the antheridia. The apical cell of the antheridial
wall, on absorbing water, ruptures by apical aperture.
 The antherozoids are now liberated to the covering film of
water

Archegonium
 Archegonia are produced close to the growing point.
 Archegonia are embedded in the tissue of the thallus.
 Each archegonium consists of an egg and a ventral canal cell
four neck canal cells.
 The canal of the archegonium is closed at the top by four
cover cells.
 These cells project slightly above the general surface of the
thallus.
Anthoceros antheridia(Microscopic view)
Female gametophyte(Microscopic view)

Development of Archegonium
FERTILIZATION:
• Water is essential for fertilization.
In the mature archegonium, the venter canal cell, neck canal
cells disintegrate and form a mucilaginous mass.
• It absorbs water, swells up and becomes out of the
archegonial neck by pushing the cover cells apart
• This mucilaginous mass becomes continuous with the
mucilage mound and in this way an open passage down to egg
is formed.
Fertilization The mucilaginous mass consists of chemical
substances.

Many antherozoids caught in the mucilage enter in the
archegonial neck because of the chemotactic response, reach up
to the egg, and fertilization is affected.
Prior to fertilization, egg enlarges and fills the cavity of the
venter.
Fusion of both male and female nuclei results in the formation
of diploid zygote or oospores.
Fertilization ends the gametophytic phase.
Sporophyte Stage
 The sporophyte of Anthoceros has certain unique features.
Sporogonium is borne on the gametophyte

 . But mature sporogonium does not totally dependent on the
gametophyte.
 The mature sporophyte consist a bulbous foot and a smooth,
slender, erect, cylindrical, structure called capsule.
 Capsule varies in length from two to fifteen centimeter in
different species. The Sporogonium appears like a ‘bristle’ or
‘horn’, hence, the species are called ‘hornworts
It has following parts
1:Foot
2:Seta
3 Capsule
The lowermost cells of the foot are haustorial which absorb water
and mineral nutrients from the gametophyte for the developing
sporophyte.
It is the basal part of the sporophyte which is a rounded bulbous
structure deeply embedded in the tissue of the thallus.
STRUCTURE OF SPOROPHYTE
It regenerates the capsule from the base, thus the capsules are
always in different stages of growth.
This is a narrow zone of meristematic cells located in-between the
foot and the capsule.
 The Intermediate Meristematic Zone

 Meristematic zone
It consists of
1. Capsule wall,
2. Sporogenous tissue
3. Collumela
It is a slender smooth upright cylindrical structure that slightly
tapers at the apex.
The capsule forms the major and conspicuous part of the
sporophyte.
Thus, the sporophyte is capable of manufacturing their own food
by photosynthesis, except for the water and minerals for which it
depends upon the gametophyte.
 Below the epidermal layer is the green parenchyma-
tous, photosynthetic tissue containing chloroplasts.
 The capsule wall is made up of 4-6 layers of
parenchymatous cells.
The cells of the outermost layer, which form the epidermis,
are heavily cutinized, vertically elongated and interrupted by
the stomata
T.S and L.S Microscopic view of Sporophyte

Dehiscence of Capsule
Proskauer (1948) studied in great detail the dehiscence
of sporogonium in Anthoceros, and pointed out the
customary misinterpreted of the method of dehiscence
According to Proskauer when the tip of the sporogonium has
assumed the black or brown coloration characteristics of the
respective species, the capsule is ready for dehiscence, a process
that depends on water loss

Mature sporophyte of Anthoceros
A. L.S Different portions are shown magnified on the right hand side
B. T.S at the middle of the sporophyte
C. A stomata in the jacket epidermis
D. Ruptures tip of a mature sporophyte capsule
Anthoceros, Sporophyte
(Longitudinal section)
Germination of Spores
The Germination of spores has been studied by
Camphell in A.fusiformis and by Mehra and Kachroo
(1962) in A.erectus and A.punctatus

 Each spore has an outer thick wall exosporium and an
inner thin wall endosporium. The spores undergo a period
of rest of few weeks or months.
 The outer wall ruptures during germination. The inner wall
 The cells of the protonema become green.
 The apical cell of protonema form thallus.
 Sincoth rhizoids come out from certain cells of the lower
surface.
 They fix the thallus to the soil.
 Some mucilaginous cavities also develop at the lower side.
Nostoc filaments enter through these tubes.
Spores(Microscopic view)

EVOLUTIONARY TRENDS IN ANTHOCEROS
A general survey of the gametophyte and sporophyte
generations of Anthoceroles leads to the conclusion that
the group has features in common with the Algae on the
other hand to other group of Embryophyta on the other.
Features common with algae:
1. Simple, green thallus-like plant body and its branching.
2. Presence of a single chloroplast with pyrenoids in each cell of
the thallus.
3. Biflagellate antherozoids with whiplash flagella.
Features common with liverworts
Hepaticopsida:
1. Apical growth of the thallus .
2. Gametophyte structure (thallus) resembles Pellia (liverwort).
In both the members, scales and tuberculate rhizoids are
absent.
3. Similarity in the construction of mature sex organs.
Features common with mosses (Bryophyta):

1. Presence of central collumela in the capsule
2. The sporogenous tissue is greatly reduced.
3. Presence of functional stomata in the capsule wall
4. Archesporium differentiates from the inner layer of
amphithecia as in Sphagnales.
Features common with Pteridophytes:
1. General similarity in the thallus structure of Anthoceros and
the fern gametophyte (prothallus).
2. The sunken sex organs (sunken)
3. Similarity in the structure of mature archegonium.
4. Highly developed semi-parasitic sporophyte of
indeterminate growth showing photosynthetic capsule wall
with functional stomata.
The features of Anthocerotophytes that are common with lower
group of plants, i.e., algae, and the higher groups of plants, like
liverworts, mosses and Pteridophytes, suggest that the
Anthocerotophytes are a distinct but synthetic group of plants.
All the facts enumerated above suggest that the
Anthocerotales are a distinct but synthetic group of
plants.
Camphell (1928) suggested that despite the similarities
between the Sporophyte of the liverworts as
Sphaerocarpos and the Anthocerotales.

Pande stated “This fact suggests a close relationshop
between the groups and favours the retention of the
Anthocerotales in the Hepaticae.
In addition the sporophyte of Anthocerotales also shows
probable lines of biological progress in the following directions:
I. The presence of complex photosynthetic mechanism,
consisting of intercellular spaces in the green tissue and an
epidermis with functional stomata, may suggest the
beginning of the physiological independence of the
sporophyte.
II. The breaking up of continuos sporogenous tissue into
separate smaller masses by the growth of sterile cells
between the spore mother cells may suggest the beginning of
the formation of sporangia.
III. The establishment of a central sterile portion, the collumela,
by the transfer of sporogenous tissue from the central
endothecium to the peripheral amphithecium may suggest
the beginning of a region for the development of conducting
system, and the initial stage in the formation of superficial
sporangia.
IV. The establishment of an intercalary merismatic region may
suggest the beginning of interemediate growth of the
sporophyte.

REFERENCES
All the facts and information were used by following
sources
 Book by N.S Pariharon byrophytes
 flickr images
 http://www.biologydiscussion.com/bryophyta/a
nthoceros-gametophytic-and-sporophytic-
organizations/21365
 http://magbin.net/anthoceros-life-cycle-structure/
 http://www.indefenseofplants.com/blog/2018/12/1
1/an-introduction-to-hornworts
 https://biologyboom.com/type-anthoceros/

THANKYOU
That one plant should be sown and another be produced cannot happen;
whatever seed is sown, a plant of that kind even comes forth.
Guru Nanak

Anthoceros

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