Final answer:
The sporangia of ferns are found in clusters called sori on the underside of fronds, and the opening mechanism involves specialized cells called the annulus.
Step-by-step explanation:
Location of Sporangia on a Fern
The sporangia of ferns are generally located on the underside of their fronds. In most fern species, these sporangia are grouped into clusters known as sori, which appear as small bumps or 'fruit dots' on the frond's surface. The release of spores from the sporangium is a crucial part of the fern's life cycle, leading to the generation of gametophytes. The sporangia themselves contain spore mother cells that undergo meiosis to produce haploid spores.
When these spores are released into the environment and germinate, they form new haploid gametophytes, thus repeating the life cycle. Certain specialized cells, named the annulus, facilitate the opening of the sporangium to release spores by snapping back rapidly when the tension from drying surpasses the strength of the water columns holding the cells together.