C. Pteridophyta
(Pteron : feather, phyton : plant)
Evolutionarily, Pteridophytes are the first vascular and true land plants. Hence considered as the first successful terrestrial plants with true roots, stem and leaves.
These plants have a primitive conducting system and they are the only Cryptogams with vascular tissues.
The late Paleozoic era is regarded as the age of Pteridophytes.
The group has about 400 genera and 11,000 species.
The plants consist of pinnate (feather like) leaves.
Leaves may be small called microphylls (e.g. Selaginella) or large called macrophylls (e.g. Nephrolepis /fern).
Pteridophytes grow in moist and shady places.
Pteridophytes show sporophytic and gametophytic stages in life cycle, e.g. Ferns, Horsetail.
Some are aquatic (Azolla, Marsilea), xerophytic (Equisetum) and epiphytic (Lycopodium).
Pteriodphytes show heteromorphic alternation of generations in which the sporophyte is diploid, dominant, autotrophic and independent.
It is differentiated into root, stem and leaves.
The primary root is short lived and soon replaced by adventitious roots while the stem may be aerial or underground.
Leaves may be scaly (Equisetum) simple and sessile (Lycopodium) or large and pinnately compound (Nephrolepis / Ferns).
In these members, Xylem consists of only tracheids and Phloem consists of only sieve cells.
Secondary growth is not seen in Pteridophytes due to absence of cambium.
Pteridophytes are classified as -
Psilopsida-(Psilotum),
Lycopsida - (Selaginella and Lycopodium),
Sphenopsida - (Equiesetum) and
Pteropsida - (Dryopteris, Pteris and Adiantum)
Economic importance -
Pteridophytes are used for medicinal purpose and as soil binders.
Many varieties are grown as ornamental plants.
1. Distinguish between Bryophyta and Pteridophyta.
2. Why Bryophyta are called amphibians of Plant Kingdom?
3. Pteridophytes are also known as vascular Cryptogams - Justify.
4. Give one example of aquatic and xerophytic Pteridophytes.
