Paleobotany Calamites,Lyginopteris, Pentoxylon, Lepidodendron.pptx

Paleobotany
Calamites,Lepidodendron, Lyginopteris, Pentoxylon, Contribution of Birbal sahni

1. Paleobotany Calamites Lepidodendron Lyginopteris Pentoxylon Contribution of Birbal Sahni Ms. Ankita A. More -Ms. Ankita Avinash More GATE, SET

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3. Ms. Ankita A. More Calamites

4. Paleobotany is the scientific study of ancient plants, using plant fossils found in sedimentary rocks. Calamites Habit and Habitat :- Calamites possessed an arborescent (resembling a tree) habit . The genus appeared in the upper Carboniferous , flourished luxuriantly in the Devonian and then become extinct in the Early Triassic. The fossil remains are rather commonly found , though fragmentaty (consisting of small disconnected or incomplete parts ) forms. Ms. Ankita A. More

5. External Features of Calamites : The calamitean fossils range from pith casts , stems, twigs and leaves to strobili . In the strict sense , the generic name Calamites should be applied only to pith casts of stems and branches The stem is known as Calamities , leafy twigs are called Annularia , and fructification is known as Calamostachys . The plant body of Calamites was a tall tree growing to a height of 20-30 metres . The plant had an underground prostrate rhizome. The rhizome was differentiated into nodes and internodes and had a whorl of adventitious roots at each node. From the upper surface of the rhizome arose a number of aerial shoots. Ms. Ankita A. More

6. Some of these aerial shoots produced roots at some of the lower nodes, indicating that rhizome grew at some distance below the surface of the soil. Erect shoots were constricted at the point of their junction to the rhizome. The branching was conspicuous in the aerial shoots which had whorls of branches at the nodal region . The mode of branching is varied and it is used as a criterion in classifying the genus. Based on the branching pattern three sub-genera have been founded. In Stylocalamites the branches are few and scattered (e.g. C. suckowi ). In Calamitina , whorls of branches are present only at certain nodes, (e.g. C. undulatus ). In Eucalamities , branches are borne at every node (e.g. C. cerinatus and C. cruciatus ). Ms. Ankita A. More

7. The lateral branches of the aerial shoots in some cases persisted for a long time and were as thick as the main axis giving the familiar appearance of the present day Equisetum, but much larger in size. The surface of the stem had longitudinal ribs alternating with the grooves. But in some instances the ribs of the successive internodes were directly above instead of alternating with one another . The external surface of the stem of Calamites exhibited ribs and furrows , as are noted in Equisetum. Ms. Ankita A. More

8. Internal Structure of Calamites: Anatomically the stem of Calamites showed an epidermis, cortex and stele. In the young stems the cortex had an outer sclerotic zone and an inner thin welled parenchymatous zone. There were no Vallecular canals as in Equisetum. The stele was siphonostelic . In the central region there was a parenchymatous pith at the nodes, but represented by a central cavity at the internodes . The vascular bundles had collaterally arranged xylem and phloem. The xylem was endarch . The tracheids had scalariform thickenings in metaxylcm but annular and spiral thickenings in the protoxylem . In each vascular bundle there was a carinal canal formed by the dissolution of the protoxylem elements  Ms. Ankita A. More

9. Secondary growth in the stem took place by the activity of a cambium . The cylinder attained a thickness of 6 cm. or more due to the secondary growth. The secondary wood did not show the differentiation of annual rings . annual rings of tree Ms. Ankita A. More

10. These point out that the plant had an evergreen foliage and there was probably no seasonal variation in a year which is responsible for the annual ring formation. Secondary xylem had scalariform and pitted tracheids . Secondary growth also took place in the cortex producing periderm of several centimeters in thickness. Ms. Ankita A. More

11. 1. Leaves: The leaves of Calamites are given the name Annularia . The foliage was found mostly on the smallest twigs. They were whorled in arrangement. Each leaf was linear or lanceolate , had a single vein and ranged in length from 4 m to 5 mm. The leaves of Calamites, which were produced in whorls of 4 to 60 at each node of aerial branches were either free form one another or united along with lower margins. Ms. Ankita A. More

12. 2. Roots: Roots of Calamites are called Astromyelon . Internally they had a direct triarch xylem with centripetal protoxylem . A cambium was present in the root, but produced only a limited quantity of secondary wood. Ms. Ankita A. More

13. 3. Strobili : The strobili associated with the Calamitean stem are given the name Calamostachys . In this, the strobilus had a central axis bearing whorls of sporangiophores . Alternating with the whorls of sporangiophores were whorls of sterile appendages called bracts. The sporangiophores had cruciately (cross shaped) branched apices. The tip of each branch recurved towards the strobilar axis and had a sporangium at the tip. The genus Calamostachys had both homosporous and heterosporous species. The strobili or cones of Calamites showed wide arrangements , the majority of them , however, belonging to either of the two genera, Calamostachys and Palaeostachya . The sporangiophores in the former genus stood out at right angles to the axis of the strobilus , while in the later case , they stood out at an angle of near about 45º. The sporangia may be either homosporous or heterosporous even in the different species of the same genus. Further in Calamostachys , the leaf bracts and sporangiophores appear in alternate whorl, while in Palaeostachya , the sporangiophores appear in the axils of the bracts. Ms. Ankita A. More

14. Ms. Ankita A. More Lepidodendron

15. Habit and Habitat :- The genus Lepidodendron with its 100 species (approximately ) appeared in the Late Devonian , flourished in the Carboniferous and then underwent degeneration most probably during the Late Permian . The plants were mostly tall trees. The plant body ( Sporophyte ): - The plant was large tree with a typical Stigmarian root system , a main trunk , which remained straight and unbranched for a considerable height and then showed a regular dichotomy in its branches. The stellar organization of the stem and branches of Lepidodendron was usually of a protostelic nature. The leaves named as the form genus Lepidophyllum , were circular to linear in shape and simple and they were borne spirally on the branches as well as in alternating whorls. The persistent leaf bases were pyramidal in outline and formed peculiar leaf cushions. Ms. Ankita A. More

16. On either side of the solitary median vascular strand of the leaf base there was a strand of parenchyma cells giving rise to the parichnos , each of which ultimately lost its identity in the mesophyll tissue. Lepidostrobus :- The name of the form genus of the cone or strobilus of Lepidodendron is Lepidostrobus which is an elliptical or cylindrical body which contained both microsporophyll, each bearing one microsporangium with numerous microspores and megasporophylls bear one mega sporangium containing lesser number of megaspores. The former lie towards the apex and the later towards the strobilus. Ms. Ankita A. More

17. Lepidodendron , extinct genus of tree-sized lycopsid plants lived during the Carboniferous Period (about 359 million to 299 million years ago). Lepidodendron and its relatives Lepidophloios , Bothrodendron , and Paralycopodites —were related to modern club mosses. They grew up to 40 metres (130 feet) in height and 2 metres (about 7 feet) in diameter. During their juvenile stages, these plants grew as unbranched trunks with a stock of long, thin leaves that sprouted near the growing tip. They branched at later stages, either in even dichotomies at the growing tip or in lateral branches that were later shed. After branching, the leaves became shorter and awl-shaped. As the plant grew, it shed leaves from older parts of the stem that left diamond-shaped leaf bases. Ms. Ankita A. More

18. The Lepidodendrales were the most elaborate and diversified of all the lycopsids , and dominated the Carboniferous , but with the drying of the climate during the latest Carboniferous and early Permian they went into a steep decline. By the middle Permian, they were all gone. Inefficient movement of water and nutrients through the stems of these tall plants, resulting from a lack of secondary xylem is cited as one of the reasons for their extinction. Ms. Ankita A. More

19. Stems were characterized by a slender central strand of wood and a thick bark. Since Stigmaria —the underground parts of the plant—resembled stems, they are not considered true roots. The shape of leaf bases and the arrangement of their vascular strands distinguish the different genera within the group of arborescent lycopsids . Ms. Ankita A. More

20. The Stigmaria had spirally arranged roots coming from them. Attached to the Stigmaria of Lepidodendron was a long pole-like trunk which had no branches for most of its length. T he trunk terminated in a crown of simple branches which were covered with spirally arranged grass-like leaves, called Lepidophyllum . At the end of the branches were reproductive cones, called Lepidostrobus , which contained spores. These different names (called "form genera") have been applied to different parts of Lepidodendron because they were originally discovered and scientifically described as separate parts. It was only later when more complete specimens were found that it was realized that the separately described parts in fact belonged to the same plant. In some cases the form genus turns out to belong to different families when the complete plant is considered. For example Stigmaria may belong to genera assigned to Lepidodendraceae , Sigillariaceae , or Lepidocarpaceae Ms. Ankita A. More

21. Roots Lepidodendron and similar great trees grew in the hot humid swampland of the Carboniferous period. It possessed branching rooting organs, called Stigmaria , by which it was anchored in shallow soil. In all the members of Lepidodendrales , the root-bearing underground axes are called rhizomorph and the detached rhizomorph and their roots are called Sigmaria which are mostly found as siliceous casts or molds . Stigmaria ficoides , the commonest species of Stigmaria , was a large trunk base that divided dichotomously into four large massive descending axes Ms. Ankita A. More

22. Stem The stem form-genus is called Lepidodendron which has been reported mostly as casts or compressions. In most species, the trunks attained a height up to 98-115 ft (30-35 m), because the first branching at a distal end appeared up to 30-35 m in height. At the base, the trunks are known to be 3.3 ft (1 m) in diameter. Numerous leaf cushions arrange spirally on the stem surface. The leaf cushions-are rhomboidal in shape and broader in their vertical dimension than their transverse length. A leaf scar is situated just above the middle line of the cushion. The leaf scar comprised of a vascular bundle scar at the centre. Ms. Ankita A. More

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26. Many of the larger lepidodendrid trees had monosporangiate cones, with highly specialized megasporangia that mimic the seed habit. A good example is Lepidocarpon . In Lepidocarpon cones, there is a single megaspore present that remains within the megasporangium , and the megasporangium remains tucked inside a leafy sporophyll that encloses it. The entire cone breaks up and these units thus serve as propagules . Because plants bearing this type of cone were living in a wet coal swamp, some paleobotanists have suggested that this dispersal unit acted as a small boat capable of aquatic dispersal. Ms. Ankita A. More

27. Lepidodendron ( Knorria ) Lepidodendron is the name (= form-genus) for impressions of the outer bark of large arborescent lycophytes.Lepidodendron is also the name that paleobotanists use to refer to the biological genus for entire plant, including all of its individual parts. Lepidodendron grew to over 100 feet (30 meters) tall and preferred the wetter, but not wettest areas in swamps. Lepidodendron is recognized by the diamond-shaped pattern of leaf scars that spiral around the trunk of the tree; each scar being generally taller than wide.During the life of the tree, the outer bark of Lepidodendron trees would be shed revealing the layer beneath. This inner bark layer displayed a different pattern and is given a separate and distinct name, called Knorria , when found in the fossil record. Ms. Ankita A. More

28. Reproduction Lepidodendron and its relatives reproduced by spores, with megaspores giving rise to the female (egg-producing) gametophyte and microspores giving rise to the male (sperm-producing) gametophyte. Lepidophloios wrapped its megasporangium in a layer of tissue much like that of the seed plants. This feature, however, was independently derived in the lycopsid lineage. In some genera, spore-bearing cones were produced at the tips of branches, suggesting that the plants could reproduce only once in their lifetime. Lepidodendron and its relatives lived in the extensive peat forming swamps and became extinct when these swamps disappeared Ms. Ankita A. More

29. Reproductive Structure Lepidodendron formed bisporangiate cones called Flemingites that were borne terminally. The sporophylls were helically attached to the central cone axis. The microsporophylls bearing microsporangia were usually borne in the apical portion, while megasporophylls bearing megasporangia occupied the basal portion of the cones. Morphologically, both the sporophylls were identical, except for their spore content. The microspores were small, about 25 mm in diameter, with smooth or granular exine . The cones containing only microspores are assigned to the form genus Lepidostrobus , possibly a monsporangiate cone of Lepidodendron Ms. Ankita A. More

30. Megaspores were spherical, slightly elongated, showing trilete aperture with echinate ( spinous ) exine . Ms. Ankita A. More

31. Lepidocarpon : a False Seed The female gametophyte of Lepidodendron is called Lepidocarpon . Like a spermatophyte (especially gymnosperm), the megagametophyte ( Lepidocarpon ) is retained within the megasporangiun and the sides of the pedicel were extended to lorm lateral laminae , called integuments —which completely enveloped the sporangium. Seed characteristics of Lepidocarpon (similarity with an ovule of gymnosperm): 1. Formation of a single functional megaspore in the megasporangium . 2. Retention of functional megaspore in the megasporangium . 3. Formation of endosporic megagametophyte within megasporangium . 4. Formation of an integument that delimited a microphyle . All of the above characteristics show that Lepidocarpon apparently possessed the attributes of a seed habit. However, it did not reach the level of a seed (ovule), because the basic characteristics of a seed (ovule) are totally absent in Lepidocarpon . Ms. Ankita A. More

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33. C ontribution of birbal sahni , birbal sahni institute of paleobotany lucknow Ms. Ankita A. More

34. A very distinguished scientist who laid the foundation for the study of Botany in India is Prof. Birbal Sahni who had special interest in Paleobotany . He was born in the year 1891 and his hometown was Bhera in the state of Punjab. His father was Prof. Ruchi Ram Sahni who specialized in Chemistry . After graduating from Lahore in 1911, he continued his studies at the University of Cambridge. Ms. Ankita A. More

35. Early Life and career After his studies at Cambridge,  in 1914 he started his research in Botany under Prof. A. C. Steward. He  was given the responsibility of revising the “Textbook of Botany”  by Lawson which showed his profound knowledge of Indian plants. In 1919 he was awarded the Doctor of Science  by the University of London for his studies on Paleobotany . On returning to India in  the same year he  was in-charge of Botany Departments at the Banaras and Punjab Univerisites . In 1921, he was given charge of the Department of Botany at Lucknow University as its first professor  and later became Dean of sciences in 1933. Ms. Ankita A. More

36. He held both these posts until his death. When  the  Geology Department was started in 1943,  he became the professor of Geology as he had also studied Geology  . Highlights of career Prof. Birbal Sahni was the first  Indian Scientist to receive the  Doctor of Science Degree. He was the Honorary Professor of Botany at the Banaras Hindu University. He was elected Vice- President of Paleobotany section  in the 5 th  and 6 th   International Botanical Congress. He officiated as the President of the National Academy of Sciences for two spells -1937 to 1939 and 1943 to 1944. Ms. Ankita A. More

37. He was President of Botany Section at the Indian science Congress in 1921 and 1938 and held the position of General President at the Science Congress held in 1940 . He was also elected the President of the International Botanical Congress to be held at Stockholm in 1950 but he suddenly passed away in 1949  before  the event could take place/ He was designated by the Government of India to visit Research Laboratories in Europe, The United Kingdom and The United States of America to observe and set up research laboratories in India after Independence in 1947. He was awarded Fellowship of most of the learned Societies in India. Ms. Ankita A. More

38. Awards and Honours He received the Barclay Medal by the Royal Asiatic Society of Bengal for outstanding researches in Biological sciences. He also received the Sir C. R. Reddy National prize for Natural Sciences  in 1947. He was awarded the Honorary Doctorates by the Universities of Patna and Allahabad. He received the Nelson Wright Medal of the Numismatic Society of  India in 1945 for his article on the art of casting coins in Ancient India. Ms. Ankita A. More

39. Important Contributions of  Prof. Birbal Sahni Though a Paleobotanist , most of his work was concerned with living plants Between 1915 and 1936 he did a lot of work on morphology and Phylogeny of Pteridophytes and Gymnosperms like  Nephrolepis , Tmesipteris , Taxus , Cephalotaxus  and  Ginkgo . He contributed important landmark articles like “Observations on the branching in Filicales ” (1917) and “The Ontogeny of Vascular Plants and Theory of Recapitulation” (1925 )/ He studied the age of the Saline series of Punjab Salt Range and Deccan traps  -his conclusion that they are of tertiary age is still accepted. He published his researches on the Zygopteridaceae in 1918. He collaborated with Prof. Seward and revised the Indian Gondwana plants and gave important data on Indian fossil conifers. Ms. Ankita A. More

40. Between 1918 and 1949 he published articles on every aspect of Paleobotany He described many fossil materials from India. He started and edited the Research Bulletin called “ Paleobotany in India ”. He contributed his observations that solved the problems related to Paleographics and Geology of Permo -Carboniferous life provinces. He contributed his ideas to explain Wegner’s theory of Continental drift and Himalayan Uplift. The fossiliferous areas that interested Prof. Sahni were the RajMahal Hills of Bihar, The deccan series and the Salt range of Punjab. Ms. Ankita A. More

41. He described a number of fossil forms including Homoxylon rajmahalense , Rajmahalia paradoxa and Williamsonia sewardiana . His notable contribution was the institution of a new group of extinct plants –the Pentoxyleae . He was instrumental in setting up the Institute of Paleobotany   at Lucknow    which is called the Birbal Sahni Institute of Paleobotany . Ms. Ankita A. More

42. Lyginopteris Ms. Ankita A. More

43. Morphological Features The stem Lyginopteris was slender and covered with large scaly leaves. Near the base of the plant adventitious roots developed. The plant seems to have been a climber. Lyginopteris oldhamia also known as Calymatotheca hoeninghausi was described in detail by Williamson, Scott, Brongniart , Binney , Potonie , and Oliver and Scott. It was found abundantly in the horizon of Lancashire and Yorkshire [England]. Ms. Ankita A. More

44. Anatomical Features The Primary structure was an ectophloic siphonostele with large pith round a number of primary mesarch bundles. Older plants showed normal secondary growth. In some specimens, however, the xylem portion of primary vascular bundles was in a continuous ring. In some there was an abnormal type of secondary growth. This abnormality was of two forms, either there was an inner ring of secondary phloem developed or it was that the cambium appeared in strips found separately in vascular bundles giving rise to a polystelic appearance. Ms. Ankita A. More

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48. Reproductive Structure of Lyginopteris : Some of these Palaeozoic leaves bore microsporangia on them. The fertile pinnules were more or less peltate in form and on their underside they bore usually six sporangia. These sporangia are usually bilocular . Such a type has been described as Crossotheca type. The microspores seem to have formed a male prothallus . The male spores seem to have been of like those of present-day cycads. Ms. Ankita A. More

49. Seed of Lyginopteris The best known seed has been described under the name Lagenostoma . These seeds were small in size, only about 1/4 but they were highly organized. It was barrel shaped and whole seed enclosed in cupule . This cupule opened out when seed was mature. Each seed was borne at the tip of stalk. The cupule rised from the base of the seed but not fused with it. The cupule was in three main lobes. These lobes were divided in the upper parts of the seeds. The seed or ovule was orthrotropus and of cycadian type. It was radially symmetrical. The cupule was separated from the seed along its entire length. The seed itself has an integument which surrounded the nucellus . The integument and nucellus were fused except at the top. The integument formed nine projections. In each of these projections there was a vascular bundle present. Ms. Ankita A. More

50. In some the megaspore membrane is very well seen. In the centre of the seed there was a tissue but so far neither any archegonium nor any embryo has been found in these Palaeozoic seeds. The seeds were borne at the tips of the stalks. They were not organized to form cover. In addition to this Lagenostoma there are many other Palaeozoic seeds which have been described some simpler other more complex than Lagenostoma . A peculiar feature of all Palaeozoic seeds which so for has not been explained is the absence of any embryo in them. Pollen grains have been found in pollen chambers. Some of them had even showed their germ tube, but so far no seed is discovered in which embryo was developed. It is possible that all the seeds described might have not preserved or they preserved before embryo formation. Ms. Ankita A. More

51. Ms. Ankita A. More Pentoxylon

52. Ms. Ankita A. More Pentoxylon The pentoxylales are a group of seed plants that lived during middle to late Mesozoic period . Stems, leaves and male and female reproductive organs of this group have been described under following names: Stems : Pentoxylon and Nipanioxylon Leaves : Nipaniophyllum Pollen-bearing organs : Sahnia Seed-bearing organs : Carnoconites . They had long narrow leaves and wood in a characteristic five wedge pattern ( penta – xylon ) around the primary xylem..

53. Ms. Ankita A. More Habit The plant was probably a shrub or very small trees. The stem was dimorphic. Long and short shoots were covered with spirally arranged scale, foliage bases and terminally located reproductive organs. Leaves were thick, simple, lanceolate , had diploxylic leaf trace. The anatomy of stem revealed five to six steles which were closely aggregated.

54. Ms. Ankita A. More The stems of Pentoxylon sahnii attained a diameter from 3mm to 2 cm. Each stele had its own cambium. The cambium was uniformly active in the young stems, but at maturity more secondary tissue developed towards the centre, and thus the secondary wood appeared eccentric. Primary phloem and primary xylem were present towards outer and inner sides of the cambium, respectively.

55. Ms. Ankita A. More The wood was pycnoxylic (It is compact and strong wood. It has a large number of xylem tracheids , a small amount of pith, and cortex, and very little parenchyma) made of compact tracheids . Ovules were sessile. Female reproductive organs were like stalked mulberry, consisting of about 20 sessile seeds attached to central receptacle and surrounded by stony layer and then fleshy outer layer of integument uniting them. Male reproductive organs or microsporophyll’s form whorl of branched micro- sporangiophores . The micro- sporangiophores were fused basally into a disc-like structure.