Gametophyte:
Structure of Thallus: Plant antheroceros represents gametophytic phase of life history. It is dorsoventral plote like thallus. It is lobed with irregular dichotomous branches. Thallus remains attached to substratum by means of rhizoids which are smooth walled.
T.S. of thallus bears outer layer of epidermis and inner parenchymatous tissue. The cells have single layer chloroplast with conspicuous pyrenoid. Ventral portion of thallus has certain intercellular cavities filled with mucilage. These cavities open by narrow shits. These cavities have endophytic colonies of the blue green algae nostoc.
Reproduction: it takes place by vegetative or sexual methods.
(1) Vegetative reproduction: it takes place by:
(i) By Death and Decay:- By death and decay of older portions of thallus, younger one are separated apart which lead an independent life and grow into adult.
(ii) By gemmae formation: In some species of A.glandulosus, the gemmae formation takes place which on separation forms new thallus.
(iii) By tubears formation: in some species of A.tuberosus, A.Thalli, A.luimalayensis, A.Lacvis tubers arise on the thallus during unfavourable conditions. They get detached from the thallus and give rise to new plant.
(iv) By Persistant species: In few species like fusiformis the apices of gametophyte are capable of resisting under unfavourable conditions.
Sexual Reproduction: It is highly advanced oogamous type brought about by means of definite male (antheridium) and female (acrhegonium) reproductive organs. Usually antheroceros is homothallic or monoecious but in few archegonia are borne on the same plant but in separate group and causes may be heterothallic or dioecious. Antheridia and archegonia are borne on some plant but in separate group and usually antheridia appear first both kinds of sex organs are embedded on dorsal surface of thallus and develop endogenously.
Male Reproductive Organs: Male organs are antheridium which develops from any superficial cell of dorsal surface of gametophyte. This cell increases in size and divides by periclinal division into an inner antheridial initial and outer sterile roof cell. Antheridial initial divides into primary. Antheridial cell and a primary stalk cell.
Primary stalk cell gives rise to stalk and primary antheridial cell divides by two vertical walls at right angels to each other and then by two transverse walls. Thus forming three tiers with four cells in each tier. Sterile roof initial cell increases in size around the antheridium to form antheridial chamber. Lowest tier gives rise to the stalk while two upper tiers divide by pericinal divisions into outer primary jacket cells and inner primary androgonial cell. Androgonial cells become androcytes which metamorphose into biciliated antherozoids, the roof antheridia burst and expose ripe antheridia which absorb water and swell and break up, thus exposing the antherozoids.
Female reproductive organs: They are archegonia embedded on the dorsal surface of thallus. Any cell behaves as archegonial initial cell and functions as primary archegonial cell in which three vertical walls appear cutting off three jacket initial, or wall cells surrounding the central primary axial cell. It divides transversely into a central cell and cover initial. Central cell divides into primary venter cell and primary neck canal cell. Cover initial divides by vertical wall and form four cover cells. The primary neck canal cells divide and redivide and give rise to 4 to 6 neck canal cells.
Primary venter cell divides to form venter canal cells and egg. Mature archegonium is flask shaped.
Fertilization: Water medium is necessary for fertilization. Neck canal cells and venter canal cells of archegonium disorganise and form mucilage substance which absorbs water cover cell opens. Motile antheridia enter by this opening and one sperm fuses with one egg to form diploid oospore or zygote.
Sporophyte generation: Zygote oospore is first cell of sporophyte generation. Zygote first increases in size and fills the venter and then begins to divide by vertical furrow and again divides by vertical furrow at right angles to the first. In this way 8 celled embryos is formed with two tiers of four cells each. Upper tier of 4 cells forms the capsular region and lower tier forms bulbous foot. Upper tier of four cells divides by one or two divisions then divides by a pericinal division to form an outer amplithecium and inner endothecium which gives rise to sterile collumella.
Mature sporophyte or sporangium is exact cylindrical structure with bulbous foot and smooth slender, erect cylindrical capsule which may project above gametophytic thallus. Capsule ruptures and spores come out. Spore is first cell of gametophyte.
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