The evolution of seed habit is a significant step in plant evolution, characterized by the production of two types of spores (heterospory) and the retention of the female gametophyte within the parent plant.

Heterospory: Selaginella is a heterosporous pteridophyte, meaning it produces two types of spores: microspores (which develop into male gametophytes) and megaspores (which develop into female gametophytes).

Retention of Gametophyte: In Selaginella, the megaspore remains within the megasporangium on the parent sporophyte for a period of time, where it germinates into the female gametophyte.

Embryo Development: The zygote develops into a young embryo while still inside the female gametophyte, which is still attached to the parent plant. This phenomenon is considered the precursor to seed habit found in higher plants like gymnosperms and angiosperms.

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