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General characteristic features of Pteridophytes:
• Plant body is sporophyte (2n) and it is the dominant phase. It is differentiated into root, stem and leaves.
• Roots are adventitious.
• Stem shows monopodial or dichotomous branching.
• Leaves may be microphyllous or megaphyllous.
• Stele is protostele but in some forms siphonostele is present (Marsilea)
• Tracheids are the major water conducting elements but in Selaginella vessels are found.
• Sporangia, spore bearing bag like structures are borne on special leaves called sporophyll. The sporophylls gets organized to form cone or strobilus. Example: Selaginella, Equisetum .
• They may be homosporous (produce one type of spores-Lycopodium) or Heterosporous (produce two types of spores-Selaginella). Heterospory is the origin for seed habit.
• Development of sporangia may be eusporangiate (development of sporangium from group of initials) or leptosporangiate (development of sporangium from single initial).
• Spore mother cells undergo meiosis and produce spores (n).
• Spore germinates to produce haploid, multicellular green, cordate shaped independent gametophytes called prothallus.
• Fragmentation, Resting buds, root tubers and adventitious buds help in Vegetative reproduction.
• Sexual reproduction is Oogamous. Sex organs, namely antheridium and archegonium are produced on the prothallus.
• Antheridium produces spirally coiled and multiflagellate antherozoids.
• Archegonium is flask shaped with broad venter and elongated narrow neck. The venter possesses egg or ovum and neck contain neck canal cells.
• Water is essential for fertilization.
After fertilization a diploid zygote is formed and undergoes mitotic division to form embryo.
• Pteridophytes show apogamy and apospory.
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