Seed samples of 32 species (obligate and facultative sexuals and apomicts of monocots and dicots) were investigated by flow cytometry to reveal the pathway of reproduction. Ten different pathways of seed formation could be reconstructed considering whether the female and/or male gametes were reduced or unreduced, the embryos arose via the zygotic or parthenogenetic route and the endosperm via the pseudogamous or autonomous route. The screen is suited to select sporophytic or gametophytic mutants in sexual species, to identify pure sexual or obligate apomictic genotypes from facultative apomictic species, and to analyze the inheritance of the individual reproductive processes. Corresponding unique results are presented for Arabidopsis, Arabis, Hypericum and Poa. The screen of mature seeds by flow cytometry yielded more information about the reproductive behavior of individual plants than any other available test, and is very useful both in basic research and plant breeding.