All seed plants see concept 30.1 (page 635) view available hint(s) all seed plants see concept 30.1 (page 635) are nonvascular produce antheridia and aronia on the same gametophyte exhibit a dominant gametophyte generation produce flowers are heterosporous

Are heterosporous

This is the production of spores by plants that are in various sizes and sexes. The smaller spore is the male known as microspore and the large one is the female or the megaspores. Heterospory  evolved during a period from isospory independently in some plants such as the clubmosses, arborescent horsetails and some gymnosperms. This occured as a process of the evolution in the time of the sex differentiation in plants.

The answer to your question is vagina