Dormancy lasted about 6 months in seeds ofZizania aquaticaafterripened at 1–3 °C. Embryos lost dormancy fastest when afterripened under low oxygen tensions. Pricking the water-impermeable seed coat removed some dormancy. Low constant temperatures favored maximum rates of germination, as did alternating high and low, but constant high temperatures decreased rates. Changes in pH between 6.0 and 8.7, and a wide range of concentrations of gibberellic acid had no significant effects on germination. Air-drying of seeds for 90 days caused almost complete loss of viability; a detectable decrease occurred within 14 days. Under certain conditions, freezing caryopses also caused loss of viability. These results are discussed in relation to the habitat of wild rice.