.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. BanerJee.R.D. & Sen,S.P.(1979) have evaluated 53 species of Bryophytes for their antimicrobial and antifungal activities. Spjut.R.W.et.ai. (1986) have studied Liverworts for assessing their action against tumouroua growth. Many tjrpes of flavonoids and terpenoids are isolated by many workers all over the world. This will definitely give direction to our understanding about potentiality of Liverworts as medicinal plants. The plant body of Liverworts is differentiated into thalloid, prostrate part attached to the ground and erect sex organs. All the forms are multicellular, and the life cycle involves gametophytic generation which dominate the inconspicuous sporophytic generation which is short lived, and totaly dependent on gametophyte. The means of propagation are - tubers, persistent apices and sexual reproduction. Gametophytic plant body is minute, few centimeter in length, and water and mineral solutions are absorbed through rhizoids. Sporogonium is differentiated into foot, seta, and capsule. Sporogennous tissue is endothecial (inner layer of embryo) in origin and spores germinate to produce gametophytic plants. Merlstematic tissue in the foot region of sporophyte is absent in Hepaticae, but it is present in Anthocerotae. The Class Hepaticae is characterised by dominance of radially symmetrical or dorsiventral chlorophyllous perennial gametophyte supporting the ephlmeral sporophyte. Depending on two or three cutting faces of apical cell, various ventral or lateral units like rhizoids, scales, amphigastria are given out by the gametophyte. Male and female gametangia - the antherldia and archegonia - are aggregated into androecia and gynoecia. A broad range of variation in symmetry of thallus, 8 exists in Hepaticae according to the availability of moisture in form of water film over the thallus or capilary water below the thallus, over a varying period of time, Hepaticae are devided into.* i) Mesomorphic forms like Monocleales, Sphaerocarpales, Calobryales, Metzgeriales, Jungermanniale and ii) Xeromorphic forms like Marchantiales. Marchantiales are well orgalsed in thallus structure having - a) Unistratose dorsal epidermis with air pores b) Chlorophyllous aerenchyma. c) Massive parenchymatous ventral tissue lined by ventral epidermis giving out scales and rhizoids. Growth of thallus :- It is effectd by a cuneate apical cell with four cutting faces. Branching may be lateral - due to dichotomy - or ventral. Apical inovations as seen in Plagiochasmai sps. result due to variable activity of apical cell. Epidermial air pores result due to varying degree of activity by epidermal cells and their wall thickenings. In Xeromorphic taxa like Plagiochasma and Asterella secondary air chambers are developed by thickening in the cell wall of primary chambers. This subsequently result to form air chambers in the chlorenchyma tissue on dorsal side of the thallus. Ventral scales in these xeromorphic forms contribute to the protection of ventral epidermis and thus the thallus, by covering the rolled thallus in dessicated condition. The significance of dimorphic rhizoids in these xeromorphic hepatics is still not known. Ganetangial systen :-

Form and organisation of gametangia show great variation in Marchantiales. Corsinia and Cornisist exhibit the linkage between Riccia type diffuse acropetal gametangial arrnagement and Mar chantia type aggregated gametangial arrangement. Asexual reproductioB :-

In general, specialised devices that allow asexual propagation occur more frequently in Jungermanniidae, than in Marchantiidae and within Jungermanniidae, they are absent in Calobryale. Gemmae are common to most of the members of Marchantiidae - both promitive and advance. In Lejeuniaceae, discoid gemmae to caducous leaf lobes - all variations of asexual reproductive devices are seen in increasing frequency from Ptycanthoidae to Tuyamaeloideae. In Jungermanniales and some Metzgeriales, following leaf derived asexual devices are seen - i) Entire leaf or tip of leaf is caducous smd for a short distance, it disperse the mother plant. ii) Catenate gemmae (1-5-celled) formed by dedifferentiation of leaf apices. iii) Discoid and lamelliform gemmae - Developed by dedifferentiation of marginal cells of leaves or lateral wings of stem. iv) Endogenous gemmae - Two-celled gemmae developed from epidermis. v) Caducous and fragmenting perianth. Stem derived asexual reproductive propagules : i) Cladia - Abbreviated axis with constricted base and a 10 collar arising basiscopically and i*ea-clily detaching from the stem. a) Paranchymatous gemmae and tubers. These are developed in few mesomorpohic taxa that are adapted to seasonaly arid conditions. Tubers are exclusively produced in Marchantiidae, b) Brood branches. In Pellia endiviifolia (Dicks.)Dum. thallus apices show abruptly grown rapid, repeated bifurcations to develop a crispate system of multiramose branches. These branches do not grow further but get detached easily. PevlO^S fagllltatlag SSSXm dispersal :- In most of the Marchantiales, distinct splash-platforms which are sessile, are developed on the thallus. Both anbheridium and archegonium develop superficially in the Hepaticae. Archegonium is individually protected by a perianth as in Marchantiales or grouped together to form a gynoecium. The gynoecium is protected by upgrowth of thallus, mucilage papillae or leaf derived structures such as perichaetial leaves. In addition to these devices, a tuft of capillary hairs or scales is developed surrounding the archegonia. This helps in water retention and thus facilitate fertilisation. In Jungermanniales, at the time of fertilisation, female bracts are differentiated from leaves (Ja»esonieJJa) or a juvenile perianth is developed. Those forms in which such perianth is not formed (Trichocoleaceae) a bulb- like mass full of scales which are dissected and ciliate is developed near archegonia. 11

FrotectiPn Ol developing sporophyte j^ i) Unistratose cylindrical perianth - like structures around gyoecium ii) Pseudoperianth around individual archegonia. ill) Stem derived or receptacle derived structures like stem perigynia, marsupia, coelocaules and calyptral perigynia iv) Upgrowth of surrounding thallus. Perianth may develop from differently located potential meristematic tissuj? below the fertilised archegonia.

Fossil Record :- Late Silurean ^ Devonian^Carboniferous Hepaticae. 1) Sporogotiites Halle. Andrews (1960) found masses of these unbranched radial erect sporophytes. Its affinities to Hepaticae is doubtful since its spores (20-25/im) are not associated with elaters. ii) Pallavicinites Schuster with Pallavicinites dBvonicus (Hueb.)Schust. of lowermost Upper Devonian. This is a terete gametophytic axis formed of elongated cells with cortex and rhizoids, HepaticitBs devoTticus described by Hueber (1961) belongs to Metzgeriales and is comparable to Pallavicinia and Synphyogyna. iii) Trmubites Schust. (1966) with Treubitss kidstoni (Walt) Schust. (Hepatzcites kidstoni) of lower Carboniferous, iv) BJasiites Schust. with Blasiites lobatus (Walt)Schu3t. of LDwer Carboniferous. It has two rows of flat, coarse, lateral scallops arising from a compressed thin frond. 12 v) Metzger iothallus Schust. with Hetzger iothallus metzgerioides (Walt.)Schust.of lower Carboniferous similar to Riccardia, H^SQZQiQ H^Paticae and Anthocerotae A) Triassic-Jurassic Hepaticae : SchizolepideJla gracilis (Halle 1913) is firt recorded Jungermannidae. Marchantiales from Jurassic are represented by Porosus Lundblad (1954) and Ricciosporites tuberculatus Lundblad (1959). Naiadita Buckm.(Harris 1939) was growing in large colonies, reminiscent of modern Riella. But Kra3silovCi*^^> favours a Calobryalean affinity to Naiadita. Krassilov (1970) described a rather advanced member of Jungermanniales as Cheirorhiza brittae which shows branching, bifid leaves, reduced undeyleaves and scattered rhizoids. He has also described a Jurassic genus LaticauJina referred to Jungermannniales.

Crgtacgc>us Hepatigae and Anthocerotae. Jar2enCl979)has reported spores of Phaeoceros Prosk. But Anthocerotalean sporophyte is represented only by Paleocene (Chitale & Yawale 1980), Early Cretaceous Harchantities hallei Lundblad (1955) and Str iatothallus adanicanicus Krassilov (1973). Late Cretaceous Marcbantites jimboi Krysht.(Krassilov 1979). HBpaticites discoides Douglas (1973) and Hotothylacites filiforuis Nemej and Pacltova. Cretaceous fossils other than Marchantiales are as follows:- 3unger9auuitBs cretaceous Berry (1919) and Jungermannites noterocladioides Scott (1980). Diettetia uontanensis Brown Robison (1974) is characterised by the branching pattern and complicate bifid leaves of Jungermaniales type combined with 13 a wholly anomalous cell type. Tertiary s^n^ Quaternary fossils. Quaternary includes last 1.6 million years having two divisions - Pleistocene and Holocene. The term subfossil is used for Quaternary fossils because they are relatively young, or the tisues are usually not premineralised or coalified. Coenozoic fossils:- Tertiary - Riccardiat palmata - amber deposit from Quaternary reported by Dickson (1973). Grolle - (1980a, b, 1981a, b)

reported Cephaloziella diuorpha (Casp.)Grolle. and Bazzania polyodus (Casp.)Grolle. These are the oldest known fossil representatives of Cephaloziellaceae and Radulaceae. frullania acutata Casp., Lejeunea latiloba Casp. and Radula sphaerocar poides are seen in amber fragment. Most of the fossils from Neogene epoch are mosses and reported from Poland and U.S.S.R.