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The Pteridophyta, commonly called vascular cryptogams, are represented by more than about 10,000 species, and are characterized by the following peculiarities:
1. Members of this group are most primitive living vascular plants such as Selaginella, Lycopodium, Equisetum etc., and also fossil vascular plants such as Rhynia, Horneophyton, Asteroxylon, etc.
2. Most of the plants prefer to grow in cool and shady places while some are xerophytic, e.g., Selaginella rupestris, and many occur in aquatic conditions like Marsilea, Salvinia, Azolla, etc.
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3. Plant body is sporophytic and differentiated into roots, stem and leaves. In some plants an intermediate stage between root and stem, i.e., rhizophore, is present as in Selaginella.
4. Young sporophyte is partially or completely dependent on gametophyte for some time, but at maturity it becomes independent.
5. The fibro-vascular cylinder, consisting of xylem, phloem, etc., is present in the stem of these plants.
6. In lower members, the stele is protostele, as in Lycopodium, Selaginella, etc., but it is siphonostele in Marsilea (amphiphloic), Equisetum (ectophloic), and dictyostele as in Pteris, Aspidium, Polypodium, Dryopteris, etc.
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7. Vascular supply to the leaves takes place by leaf traces through leaf gaps of the vascular cylinder of stem.
8. Leaves may be simple, small and sessile, as in microphyllous types such as Selaginella, Lycopodium, etc., or very large, petiolate and megaphyllous types as in the members of Filicinae.
9. Plants reproduce by the spores formed in sporangia. Sporangia develop either on the ventral surface or in the axil of leaves.
10. Plants may be homosporous, i.e., all the spores are of one type as in Equisetum, or heterosporous, i.e., two types of spores are present (microspores and megaspores) as in Selaginella.
