The occurrence of plants producing 2n pollen was ascertained in nine diploid (2n=2x=14) subspecies of the polyploid grass complex Dactylis glomerata by determining the ploidy level of the progeny in 100 tetraploid (4X) × diploid (2X) crosses. The possibility of using pollen size to screen for plants which produce large quantities of 2n pollen was tested by comparing the frequency distributions of pollen diameter in plants which did and did not produce 4X progeny in an interploidy cross. The ploidy level of the progeny was determined by chromosome counts or nuclear DNA quantification using flow cytometry