Meiotic studies ofHyparrhenia hirta(L.) Stapf revealed aneuploidy with 2n=36, 54 and 56 chromosomes. The plants with 2n=54 chromosomes had much wider distribution than the other two types of plants. Diakinesis and metaphase I revealed a very high multivalent ratio. It is argued that the formation of multivalents is mainly due to the loss of chromosomes carrying genes which suppress multivalent formation. Furthermore, scarcity of autopolyploidy in nature is attributed to the gene-controlled pairing of chromosomes blurring the difference between auto-, allo-, and segmental allopolyploidy. Some of the multivalent associations might be partly due to translocation and other kinds of chromosomal rearrangements.