Q.How are the male and female gametophytes of pteridophytes and gymnosperms different from each other?

The gametophytes of pteridophytes and gymnosperms differ mainly in whether they are free-living.

• In pteridophytes, the gametophyte (prothallus) that develops from a spore is an independent, free-living, photosynthetic structure exposed to the environment, needing cool, damp conditions and water for fertilisation.
• In gymnosperms, neither the male gametophyte (the pollen grain) nor the female gametophyte ever becomes free-living; both stay enclosed within the sporangia, which themselves remain attached to the parent sporophyte. …

In pteridophytes, the spore released from the sporophyte's sporangium germinates into a gametophyte, the prothallus, that leads an entirely independent existence away from the parent plant. This prothallus is small, thalloid and photosynthetic, and it bears its own antheridia and archegonia; it must find cool, damp, shady conditions to survive, and fertilisation still depends on a film of water through which the motile antherozoids swim to the egg.

Gymnosperms show a very different arrangement. Their microspores, formed inside the microsporangia of male cones, develop into an extremely reduced male gametophyte -- just a few cells -- while still inside the microsporangium; this reduced male gametophyte is the pollen grain. Likewise, the megaspore that survives after meiosis develops into a multicellular female gametophyte, bearing archegonia, but this too stays enclosed within the megasporangium, which is itself part of the ovule attached to the megasporophyll. …