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

(N/A) $\rightarrow$ The life cycle of a fern (e.g.,$Dryopteris$) exhibits a clear alternation of generations. The haploid gametophytic stage $(n)$ alternates with the diploid sporophytic stage $(2n)$.
$\rightarrow$ Prothallus: The prothallus of a fern is a small,multicellular,free-living,photosynthetic,thalloid,and haploid structure. It is produced from haploid spores that are formed via meiosis in the sporangia of the sporophyte. Upon germination,the spore develops into a filamentous structure,which eventually grows into a heart-shaped,green,autotrophic gametophyte (prothallus) bearing rhizoids for anchorage and absorption.