Fern spore germinates into prothallus.
Explanation:
Ferns are members of phylum pteridophyta, the vascular cryptogams.
These are first land plants which are known to have a distinct conducting system of xylem and phloem.
They reproduce by forming spores that germinates into a heart shaped gametophyte.
The gametophyte of the fern is called prothallus.
The heart shaped gametophyte has root like structure called rhizoids.
These rhizoids anchor the gametophyte to the substratum.
