Anthoceros ppt. 5, views ORDER: Anthocerotales • FAMILY: Anthocerotaceae • GENUS: Anthoceros; 2. SCHEMATIC LIFE CYCLE; Anthoceros is a genus of hornworts in the family Anthocerotaceae. The genus is global in its distribution. Its name means ‘flower horn’, and refers to the. became apparent that numerous features of the life-cycle had been either The genus Anthoceros was established by Micheli in , that is to say.
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The class Anthocerotopsida Anthocerotae consists of a single order, the Oife and a single family, the Anthocerotaceae, 6 genera and species. According to MullerReimers and Proskauer the order Anthocerotales includes two families, i Anthocerotaceae and ii Notothylaceae. The latter includes a single genus, i. However, according to top bryologists, there is only one family, i.
Life Cycle of Anthoceros (With Diagram) | Anthocerotopsida
About five or six genera are included in this family. Four genera are universally recognised, they are—Anthoceros, Megaceros, Dendroceros and Notothylas.
This group differs in many respects from the other Bryophyta. However, the group is placed intermediate between Hepaticopsida Hepaticae and Bryopsida Musci. The antgoceros is considered to be very important from the point of view of its morphology, because of its intermediate position between the two important groups, the Hepaticopsida and Bryopsida.
The most characteristic features of the group are as follows: The gametophytic plant body is thalloid and dorsiventral. The rhizoids are simple and smooth walled. Tuberculate rhizoids and ventral scales are altogether absent. The tissues of the thallus are not differentiated. Air chambers and air-pores are absent.
Each cell anthocefos the thallus possesses a large chloroplast and a conspicuous pyrenoid within it. The antheridia are endogenous, i. The antheridia are developed within the antheridial chambers, singly or in groups on the dorsal side of the thallus.
Useful Notes on Anthocerotopsida Order-Anthocerotales ( Words)
cycpe The sporogonium arises from the dorsal side of the thallus. It is elongated and cylindrical in structure. It consists of foot, meristematic region and capsule. It possesses intercalary meristem, and continues its growth throughout the growing season. The wall of sporogonium contains chlorophyll. The cjcle sterile portion is columella, which is surrounded by sporogenous tissue and spores.
The elaters are also present. There are five genera i. The sporogonium capsule is linear and vertical. Generally the stomata are present on capsule wall. The archesporium arises from amphithecium. The elaters are four-celled, smooth or thick-walled and with or without thickening bands. The genus Anthoceros has been discussed here in detail. About species of this genus are found throughout the world in temperate and tropical regions.
The species are moist and shade loving. About 25 species have been reported from India, by various workers.
The three common Himalayan species are, Anthoceros himalayensis, A. The above mentioned species are common in various hilly regions such as, Mussoorie, Kumaon hills, Chamba valley and other places, 5, feet to 8, feet.
Some species have been reported from South India. All the species are found in very shady and moist places. They are found in the anthocetos of the moist rocks in dense patches. According to Cavers some of the species grow on decaying wood. The species, are not at all drought resistant. The thallus is small, prostrate, dark green and dorsiventrally differentiated.
The thallus is lobed and the lobes are somewhat divided. The mid-rib is not found. The dorsal surface of anthocrros of A.
In every case the smooth walled, simple rhizoids lifd found. The ventral scales cyclw tuberculate rhizoids are altogether absent.
The thalli are dark green, because of the presence of the Nostoc colonies, which may be easily seen with the help of lens from the underside of the thallus. The anatomy of the thallus is quite simple. Internal to the upper and lower epidermis there are simple, parenchymatous cells. The cells of parenchyma are isodiametric and uniform. Air chambers and air pores are absent. Each cell contains a big chloroplast which possesses a single pyrenoid in its centre. The chloroplasts are lens shaped.
The chloroplasts of the superficial cells are longer than the chloroplasts of the other cells. According to McAllisterthe pyrenoids of Anthoceros are quite different in structure from those of Chlorophyceae. On the ventral side of the thallus certain intercellular mucilage cavities are found.
These cavities open by small openings, the slime pores on the ventral surface of the thallus.
Sometimes, the colonies of blue green algal form-Nostoc, are found in the mucilage cavities. There is no symbiotic relationship between these Nostoc, colonies, and thalli. According to Peirce these colonies, however, do harm to the thalli. The nucleus lies in the antyoceros vicinity of the chloroplast, near the pyrenoid. Sometimes the chloroplast enfolds the nucleus within it. The apical growth of Anthoceros is a controversial topic, whether it takes place by a single apical cell or by a group of apical cells.
According to Smith the apical growth anthoceris the thallus is initiated by a single apical cell.
Reproduction in Anthoceros (With Diagram)
According to Leitgeb the apical growth in this genus takes place by several marginal apical cells. According to Mehra and Handoo the apical growth in Anthoceros erectus and A.
The vegetative propagation takes place by progressive growth and death of the older part of the thallus reaching dichotomy. But this method is not so common in Anthoceros as in Riccia and Marchantia.
In certain species of Anthoceros, the thallus becomes thickened at several places on the margins. Such marginal thickenings are called, the tubers. These tubers are perennating structures. They survive anthiceros the drought conditions.
On the advent of the favourable conditions, they develop anthocedos new thalli. The tubers are formed in A. In some of the species of Anthoceros, the gemmae have been found. The gemmae have been recorded from the species, A. Each such gemma develops into a new thallus.
According to Campbell the thalli atnhoceros the species A. These apices face the drought conditions. On the approach of favourable conditions, these apices develop into new thalli.
The species of Anthoceros may be homothallic monoecious or heterothallic dioecious. Some of the homothallic species are- A. The heterothallic species are, A. The sex lige, i. The antheridia are produced singly or in groups in the antheridial chambers. The development is endogenous.
Though the antheridium develops from a superficial cell, yet it is enclosed within the antheridial chamber which does not open out by any opening.
A dorsal superficial cell of the thallus, situated near the growing apex divides periclinally giving rise to two daughter cells. According to Cavers, Campbell and Haupt the superficial cell divides transversely and not periclinally. The upper daughter cell acts as roof initial and the lower one as antheridial initial. Eventually, a mucilage filled space appears in between the roof initial and antheridial initial.
This mucilage cavity enlarges in size and ultimately becomes the antheridial chambers. The roof initial is nothing to do with the development on the antheridium. It divides and redivides several times anticlinally and periclinally giving rise to a two layered roof of the antheridial chamber.
Simultaneously, the antheridial initial develops into a single antheridium or in a group of antheridia. A single antheridium develops in A.
According to Mehra and Handooin A. Here, the antheridial initial divides many times anticlinally producing many cells and each cell thus produced, develops into an antheridium.