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Anthoceros ppt
- 2. CLASSIFICATION • KINGDOM : Plantae • DIVISION: Anthocerotophyta • CLASS: Anthocerotopsida • ORDER: Anthocerotales • FAMILY: Anthocerotaceae • GENUS: Anthoceros
- 4. VEGETATIVE REPRODUCTION • It takes place by the following methods: • Progressive death and decay of thallus. • By tubers. • By Gemmae. • By persistent growing apices.
- 5. Death and decay of thallus • Not a very common method. More common in Liverworts. • Part of lobes form a new gametophyte.
- 6. BY TUBERS • Tubers have an outer protective corky layer and resist extreme desiccation. They remain alive even after the death of the thallus. In sufficient moisture, they germinate and give rise to new plant.
- 7. By Gemmae • Some species like A. glandulosus , A. formaosae and A. fusiformis bear stalked structures on dorsal surface called called gemmae. On separation from parent thallus they give rise to new plants.
- 8. By persistent growing apices. • Species like A. pearsoni and A. fusiformis employ this method. • Mostly in areas where summer season is very dry. • All parts of thallus except apical regions become dry. These Apices later after period of dormancy for new plant.
- 10. ANTHERIDIA • They occur endogenously on dorsal surface in a closed cavity called antheridial chambers. • They enclose mass of androcytes which mature into antherozoids.
- 13. Antherozoids • The antherozoid is spindle like and biciliate. • The cilia are attached to the anterior end of the body. • The antherozoids swim in the water by the lashing moment of their flagella.
- 14. DEVELOPMENT OF ARCHEGONIUM The development of archegonium begins from a single superficial cell. This cell becomes prominent and acts as archegonial initial. The archegonial initial first divides vertically, producing three jacket initials which surround an axial cell. The axial cell divides transversely, producing a cover initial and a central cell. Thereafter, the central cell divides by a transverse wall, giving rise to a primary canal cell and a primary venter cell.
- 16. Structure of archegonium • A mature archegonium is flask-like in shape, without neck canal cells and with an egg (oosphere) in its venter. • At the top of the neck of the archegonium there are four cover cells, which become separated from the archegonium, as soon as the gelatinization of the venter and neck canal cells is over.
- 17. FERTILIZATION • Prior to fertilization, the cover cells become detached from the archegonium, and the neck canal cells become gelatinized. Through the medium of water, the antherozoids enter the mouth of archegonium. • Ultimately, one lucky antherozoid penetrates the egg, and the fertilization is effected. The male and female nuclei unite to each other, producing a zygote (oospore)
- 18. DEVELOPMENT OF SPOROGONIUM • With the result of the first vertical division, the daughter cells are produced, which are subjected to a transverse division producing four cells of equal or unequal size • These cells again divide vertically, developing eightcelled embryo, four cells in each tier. The upper tier of four cells divides transversely. This way the three tiers of four cells each have been produced. • The lowermost tier produces the foot, the middle tier produces partly the foot and mainly the seta and the upper-most tier produces the capsule.
- 19. SPOROGONIUM TISSUE • In the young sporogonium, the columella consists of four vertical rows of the cells, but later on it is made up of sixteen rows of cells. • The jacket initials divide again and again periclinally producing the 4 to 6 layered wall of the capsule. • Later on, the sporogenous tissue becomes differentiated into two types of cells, i. e., (i) the sporocytes (spore mother cells) and (ii) the sterile cells (pseudoelaters).
- 22. LIFE CYCLE IN NUTSHELL