Comment of the life cycle and nature of a fern prothallus.

Explanation

The life cycle of tern (Dryopteris ) clearly shwos the alternation of generation. The gametophytic stage (n) alternates with the sporophytic stage (2n) figure given shows its complete life cycle

Prothallus The prothalus of the fern is multicelluar, free living. thallodi, haploid and autotrophic structure. It develops form the spores produced by sporophyll after reduction division.
These spore germinate with a germtube with an apical cell and forms a filament of 3-6 cells and one or two rhizoids at the base which later develops into gametophytic plant.