Answer:
Sporangium (plural- sporangia)
Step-by-step explanation:
ALTERNATION OF GENERATIONS between haploid state and diploid state is a vivid phenomenon in the reproductive life cycle of ferns. Both generations grow independently of one another. The sporophytic phase, which is the visible fern plant, produces a structure found on the underside of the Fern's leaves or fronds called SPORANGIA. They are usually in a group or cluster called SORI. These sporangia produces haploid spores by meiosis. The spores are released and they germinate into a gametophyte.
The gametophyte produces haploid sperms (from antheridium) and haploid eggs (from archegonium) which fuses in a process called fertilization to produce a diploid zygote. The zygote undergoes mitotic growth to develop into embryo which subsequently becomes the sporophyte (fern plant). The cycle repeats continuously when the sporophyte produces spores on its SPORANGIA again.