Q.Discuss the salient features of Pteridophyta with reference to their vascular tissue, dominant generation, leaf types and economic importance, and explain why they are regarded as the first true land plants.

Evolutionary significance. Pteridophytes were, evolutionarily, the first plant group to combine true vascular tissue with a genuinely differentiated root, stem and leaves, making them the first successful truly terrestrial vascular plants. Before this group, no plants possessed both features together.

Vascular tissue. Their xylem consists only of tracheids, and their phloem consists only of sieve cells -- more primitive than the conducting tissues of seed plants. Because pteridophytes lack cambium, they show no secondary growth, so their stems do not thicken with age.

Dominant generation. The sporophyte is diploid, autotrophic and fully independent -- what we recognise as 'the fern plant' -- differentiated into a stem (rhizome or aerial), true adventitious roots, and leaves. This is a sharp contrast with Bryophyta, where the gametophyte, not the sporophyte, is dominant.

Leaf types. Leaves may be small and simple with a single unbranched vein (microphylls, e.g. Selaginella) or large, often pinnately compound, with branched veins (macrophylls or fronds, e.g. Nephrolepis, Dryopteris). Fertile fronds carry sori -- clusters of spore-producing sporangia -- typically on their undersurface.

The gametophyte and fertilisation. The gametophyte is a separate, small, short-lived, independent, non-vascular structure (a flat prothallus in ferns), bearing antheridia and archegonia. As in bryophytes, motile antherozoids must swim through a film of water to reach the egg, so pteridophyte reproduction, though the sporophyte body is fully land-adapted, still depends on moisture. …

Structure the answer around: vascular tissue detail, which generation dominates and its organs, leaf-type distinction, gametophyte/fertilisation, classification, then economic import …

• Saying pteridophytes reproduce by seeds -- they still reproduce by spores; only the vascular tissue and body organisation are advanced, not the reproductive unit. …