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Uploaded byNistarini College, Purulia (W.B) India
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Pteridohyte - A General Account

The document discusses pteridophytes, a group of non-flowering vascular plants that reproduce through spores and exhibit an alternation of generations between a dominant sporophyte and a rudimentary gametophyte phase. It outlines their major characteristics, habitats, and classification into various classes and orders based on traditional taxonomic systems. Additionally, it highlights the importance of pteridophytes in the evolutionary history of plants, with over 13,000 species known globally.

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WELCOME TO THE WORLD OF PTERIDOPHYTE N.SANNIGRAHI, ASSOCIATE PROFESSOR, NISTARINI COLLEGE, PURULIA (W.B) 723101, INDIA
PTERIDOPHYTES----------????? • A group of vascular cryptogams, non-flowering , dispersed spores experienced alternation of generation having dominant saprophytic phase and rudimentary gametophyte phase, mostly distributed in the marshy areas, appeared in the time of the Silurian period & diversified in the lower Devonian period of geological era after the colonization of the land of gametophyte directly from algae or from bryophytes as per another school of thought, more than 13000 species across the globe of which a major shares extinct in nature during the passage of evolution.
CHARACTERS OF PTERIDOPHYTES • Primitive land vascular plants both living( Lycopodium, Selaginella, Equisetum etc.) and fossils( Rhynia, Asteroxylon, Zosterophyllum etc.) • Grow in cool and shady habitat though few are xerophytic ( S.rupestris) & many are aquatic( Azolla, Salvinia, Marsilea) • Adult plant body is sporophyte differentiated into roots, leaves & stem. Rhizoids( Psilotum) & rhizophores( Selaginella) are also reported • Mature sporophyte are independent, though at the early stage of development partially of completely dependent o gametophytes • Vascular systems with xylem & phloem, stele may be protostele( Ectophloic, endophloc & amphiphloic) or Siphonostele( Solenostele & Dictyostele) present.
Characters---- • Leaves may be simple, minute and sessile( Lycopodium) or petiolate and megaphilous as in the members of Filicinae. • Reproduction through spores borne in sporangia develop either in the ventral surface or in axil leaves( sporophylls) either eusporangiate(group of superficial cells, Selaginella) or leptosporangiate manner(intial single cell, Marsilea) • Plants may be homosporous or heterosporous(Microspores & Megaspores) • Gametophyte body is prothallus developed from haploid(n) spores
Characters----------- • Prothallus is multicellular, independent autotrophic bear both sex organs-antheridia & archegonia • Water needed in fertilization to form 2n zygote • Zygote gives the saprophytic plant body • Alternation of generation is the essential part of life cycle. Most of the part of the life cycle is diploid as the saprophytic part is predominant but the gametophyte part represented by the prothallus is an important part represented by haploid state .
Alternation of generations
CLASSIFICATION • On the basis of presence or absence of seeds, taxonomists placed the vascular plants –Pteridophyta & spermatophyta.According to traditional system of classification, the pteridophytes are divided into the following classes followed by lower hierarchical taxa like orders, families , genus, species etc. • Division Pteridophyta • i. Class- Psilophytineae • Order- Psilotales,e.g Psilotum • Order- Psilophytales e.g Rhynia • 2.Class-Lycopodineae
Classification • Order- Lycopodiales eg Lycopodium • Order- Isoetales e.g Isoetes • Order- Lepidodendrales e.g Lepidodendron • 3.class Equisetineae • Order- Equisetales represented by Equisetum • Order- Sphenophyllales represented by Sphenopmyllum • 4.Class – Fillicineae • Order- Filicales e.g Dryopteris • Order Marattiales represented by Marattia • Order Ophioglossales represented by Ophioglossum & Botrychium
Classification • Order- Osmundales represented by Osmunda • Order-Fossil orders This is the traditional system of classification which is being generally introduced for the easy identification of the pteriophytes. Besides, there are number of systems that have been proposed from time to time in this regard as far as the classification is concerned. The most popular systems in this regard are ICBN Recommendations where the name of the division end with suffix phyta, subdivision by phytina, class by opsida. Smith (1955) divided Pteridophyta under 4 divisions- Psilophyta, Lepidophyta, Calamophyta & pterophyta. The wide accepted system of classification is as follows.
Classification by Smith et.al
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