Describing a vascular plant that produces two types of spores, a smaller microspore and a larger megaspore. The microspore develops into a male gametophyte (microgametophyte) stage that produces sperm, while the megaspore develops into a female gametophyte (megagametophyte) that produces eggs. All seed plants exhibit heterospory, and their haploid microspores and megaspores are produced by microsporangia and megasporangia, respectively, inside the parent plant’s reproductive organs—cones in the case of gymnosperms and flowers in the case of angiosperms. Compare homosporous. See also alternation of generations.