Jntrotructton I

.m^-C-^'^**^ LatWW^WWWW*' Jntrotructton I. INTRODUCTION. Bryophytes form an inconspicuous green mat over the soil during monsoon. With the limited sunlight available, these tiny forms flourish well in the crevices of rocks, in- between the clumps of grasses, in the cracks of bark of giant trees, and even on the exposed steep slopes of hills and plain grounds which is undisturbed by human and cattle movements. Importance of these forms lie$ in their successful struggle against the microbial life in humid environment which is otherwise quite suitable for the microbes like soil fungi, Actinomycetes and other unicellular microbes. This interesting character of Bryophytes is not very well attended even today. Present investigation is taken over with this point in mind. Systematic and floristic studies on Hepaticae in the past, in India, has yielded valuable information regarding distribution, migration and ecology of these interesting plants. Kashyap (1929) studied the Hepatic flora of Western Himalayas and Punjab Plains, Kashyap and Chopra (1932) and Chopra (1938, 1943) have done floristic work on Bryophytes in India. Information is also available on restricted local regions like Muree hills (Hameed, 1942); Assam (Kachroo,1951,1952; Robinson,1964); Pachmarhi (Pande and Srivastava 1952); Gujarat (Mahabale and Chavan, 1954); Mount Abu (Bapna and Vyas, 1962); Eastern Himalayas (Hattori, 1966); and Nainital, Western Himalayas (Bir and Chopra, 1972); Part of Deccan Plateau (Joshi & Biradar. 1984). The importance of study of Hepatic vegetation was stressed by Pamde and Srivastava (1952) in their *Priliminary survey of the Hepatic vegetation of Pachmarhi.' Pande (1958) in his presidential address delivered at the Annual Meetings of the Indian Botanical Society, Madras, Jan.1958, stressed the importance of these studies as " I earnestly feel that to achieve any success in this direction, we need whole hearted co-operation and full sympathies of all interested in these plants. I feel that the most'urgent need is to prepare regional floras, floras of various States and finally a complete flora of the Country. The elaborate data thus accumulated will not only be of immense help in preparing a complete account of Hepatic vegetation but will be equally helpful in studying the remarkable distribution patterns and common elements of our flora with other Countries and perhaps will be helpfull in elucidating some of the interesting distribution paterns connected with other groups of plants as well." Bryophytes are used by Physiologists as an experimental material for their convenient size, large cells, and relative absense of intercellular spaces and stomatae in the gametophytic tissue. Their high regenerative potentiality and the ease with which parts or whole plants can be reared, renders them an excellent material for studying various morphogenetic phenomena. Fullford (1954) and Filler et,al. (1955) and pure cultures of Hepatics by Grace Iverson (1969) indicate clearly how variable these plants are. The expression of genes can be studied in both, gametophytic and sporophytic generation of Liverworts as well as Mosses. Early discovery of sex chromosomes in Hepatics is reported by Allen (1917). Bryophytes are characterised by their distinct gametophytic and inconspicuous sporophytic generation where the latter is totaly dependent on gametophyte. Church (1919) and Evans (1939) supported the theoiry that "Primitive gametophyte was an erect leafy shoot, radially symmetrical". Kashyap (1919) held the same view and quoted numerous examples in its support. The conservatism of reproductive structures is well known throughout the plant kingdom and retention of ancestral radial foliar habit by the sexual branches of these otherwise dorsiventral leafless forms can be best explained as due to reduction. Main points in this reduction series can be arranged as follows: i) Loss of assimilatory filaments in the air chambers, ii) Simplification of pores, and iii) Gradual shifting of terminal stalk of special, erect branches bearing sex organs to the dorsal position by the continued growth of thallus and gradual elimination of the stalk. Cavers (1910) and Campbell (1891-1940) supported another theory of evolution of Bryophtes. According to them, "The primitive gametophyte was a simple, dorsiventral, prostrate thallus which was simple in external form, as well as in hisotlogical structure. Number of botanists hold the view that antheridia and archegonia of Liverworts are homologous organs and might have evolved from multicellular sporangia of algae, like those seen in present day Phaeophyceae. Davis (1903) put forward a scheme to give theoretical explaination of evolution of sex organs. First stage : Multilocular gametangia having all cells fertile and producing small and large gametes, discharged from apex of gametangium. Second stage : Sterile superficial layer was developed on the gametangia because of the adoption of terrestrial habit by the ancestral alsal form. Both the gametes in this type also were motile. Third stage : Different gametangia were produced for male and female gametes. In addition to that, only few gametes remained fertile at the base of gametangium. In male garnetangium however, all cells except jacket layer remained fertile. Forth stage : All the cells except lowermost one, became sterile in the female gametangiiam to form a structrue similar to arhegonium. In the male gametangium, number of male gametes increased and led to formation of a structure similar to antheridium in Bryophytes. Davis has mentioned Scbizomer is leibleinii 4 Draparnaldia as showing a tendency to development of such gametangia. Present views about phylogeny of Liverworts : (1) The Liverworts are a 'dead end' in the evolution like other groups such as Musci, Sporogonitales, Anthocerotales. (2) SphAerocarpus is one of the degenerate Liverworts with ephimeral gametophytes, which is an absolute erid point in evolution. It led to no other living organism and except for GBothallus, has no extant relatives. (3) Both, Marchantiales and Jungermanniales consists of a series of extant families whose interrelationships are obscure and whose affinities and directions of evolution are still debatable. (4) Metzgeriales existed by the Devonian while there is no credible evidence that the Marchantiidae (including Sphaerocarpales) evolved prior to the development of arid world climate starting with the early Nesozoic. There are no discernible contact points between Sphaerocarpales and Jungermaniidae. Probably the Hepaticae and Mosses evolved jointly from a common ancestral stalk of green algal organisms with isomorphic alternation. There is almost universal belief that Bryophytes evolved from algae, probably belonging to chlorophyceae. This algal ancestor migrated to land and became oogamous. Simultaneously altematin of generations evolved. There is no conclusive evidence whether alternation of generations was set first or whether migration to land happened first. It is known that alternation of generations has arisen independently in diastantly related taxa of chlorophyceae. Hofmeister (1851) for the first time, showed that alternation of generations exists among plants producing antheridia and archegonia. He described the pattern of regular cyclic occurrence of gametophytic and sporopphytic generations in the Bryophytes. Celakovsky (1874) introduced the terms - antithetic and homologus, i) Ant^ithetic alternation of two generations phylogenetically distinct, i.e. where a new stage (sporophyte) has been interpolated between pre-existing generations (gametophytes). ii) Homologous alternation of two or more generations phylogenetically similar to each other but differing in presense or absense of sexual organs. Considering both sporophytic and gametophytic generations, Sphaerocarpales appear to be most primitive living bryophytes while Calobryales and Jungermanniales seem to be advanced orders. There are two distinct schools of thought as to which forms are primitive and which forms are advanced. In the absense of significantly large number of fossil forms of intermediate types from various periods, it remains highly debatable question even today. Liverworts are the tiny delicate fleshy green plants which exist and flourish during rainy season. They are quite sensitive to dry conditions of atmosphere and soil. Intense light is also not tolerable by these plants. Obviously these plants grow under the protection of other plants or cave like crevices in rocks and hills. Certain degree of gradient approximately 30*^ is essential. This is for the want of constant flow of water. This water current is essential for effective fertilisation and consequent spore formation. This selective behaviour of Liverworts goes to such an extent that in some cases the plants strictly occupy erect surfaces like brick walls, vertical hill slopes and tree trunks. The term Liverwort has got a medieval connection of •Doctrine of Symbols and Curing'. In those days, it was believed that plants which produce heart-shaped leaves, are containinag those compounds which stregthen human heart. Same was true for kidney-shaped beans and blood red coloured seeds and tubers. From those days, the plants which showed typical folded or lobed flat body are called as Liverworts. But it is not proved till date, that Liverworts are either strengthening the liver function or curing liver diseases. Today however, a medicine 'Marchantine' has really appeared in market which is useful for various skin diseases, especially Dermatitis.

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