Like ferns, gymnosperms have a well-developed alternation of fgnerations. Unlike ferns, however, gymnosperms are heterosporous, that is, they produce two kinds of spores.
Microspores occur in male cones and form male gametophytes.
Megaspores occur in femlae cones and form femal gametophytes. Gametophytes of gymnosperms are microscopic and completely dependent on the large, free-living sporophyte. The last of these, the Gnetophyta, id discussed only briefly here because the phylum consists of a few rare genera. Cones are reproductive structures of the sporophyte generation that consist of several scale like sporophylls arranged about a central axis. Sporophylls, also present in ferns and their allies, are modified leaves specialized for reproduction.