First cell of the gametophyte generation in certain pterophytes as well as .

Megaspores along with microspores are associated with plants that can be described as heterosporous, with in fact the different spore type giving rise to the that "hetero" spore designation.

Ultimately an is the product of megaspore germination and subsequent mitosis.

The megaspore is produced within a type of sporangia referred to as .

Contrast homosporous plants which lack such a distinction and, indeed, often lack as well.