The plants that produce separate male and female cones and develop microspores and megaspores into gametophytes are gymnosperms.

Here's a breakdown:

* Gymnosperms are a group of seed-bearing plants that include conifers (pines, firs, spruces), cycads, ginkgoes, and gnetophytes.

* Cones are the reproductive structures of gymnosperms.

* Male cones (also called pollen cones) are smaller and produce microspores, which develop into male gametophytes (pollen grains).

* Female cones (also called seed cones) are larger and produce megaspores, which develop into female gametophytes (ovules).

The process of fertilization in gymnosperms involves the pollen grain being carried by wind to the female cone, where it germinates and releases sperm. The sperm then fertilizes the egg inside the ovule, leading to the development of a seed.