Distinguishing characters of Pteridophytes
1. The life cycle shows distinct heteromorphic alternation of generation.
2. Plant body of Sporophyte is dominant phase.
3. Sporophyte is differentiated into true root, stem and leaves.
4. Vascular tissue i.e xylem and phloem are present. Xylem lacks vessels but tracheids are present. In phloem sieve tubes and companion cells are absent.
5. Asexual reproduction takes place by spores.
6. Most pteridophytes are homosporous i.e they produce one type of spores.
A few show heterospory i.e they produce two types of spores microspores and megaspores.
7. Spores are produced from spore mother cells after meiosis in multi-cellular sporangia.
8. Sporangia bearing leaves are called sporophylls.
9. Spores on germination develop into gametophyte which is haploid, multicellular, green and an independent structure.
10. The gametophyte develops multicellular sex organs. The male sex organ is called antheridium and the female sex organ is called archegonium
11. Sex organs have a sterile jacket.
12. Antherozoids are spirally coiled and multiflagellate.
13. Fertilization takes place inside archegonium.
14. Opening of sex organs and transfer of male gametes to archegonium for fertilization are dependent on water.
15. Fertilized egg i.e zygote develops into embryo.
Ferns represent a more specialized group of higher pteridophytes with larger leaves (megaphyllous). They are world wide in distribution and grow luxuriantly in forests, mountains, valleys etc. Some common examples of ferns are Nephrolepis, Ophioglossum, Osmunda, Pteris, Adiantum, Marsilea, Azolla, Salvinia etc.