The purpose of this study was to determine if and how the two genetically distinct forms, marsh and dune, of Sporobolus virginicus, tolerate anaerobic substrates. The treatments in the hydroponic study, conducted in the greenhouse for approximately 6 months, involved growing the marsh and dune forms in aerobic, anaerobic, and alternating aeration treatments. Plants were examined for morphological and physiological responses to the aeration treatments. In response to the continuous anaerobic treatment, the dune form of S. virginicus exhibited increased stolon biomass, but no difference of total biomass or rhizome aerenchyma when compared with the aerobic treatment. In response to alternating aeration, rhizome aerenchyma increased, total biomass decreased, and stolon biomass remained constant. Below ground transport of oxygen enabled the root tissue in all of the aeration treatments to maintain aerobic respiration. Marsh form roots did not appear to be respiring anaerobically or producing ethanol or additional malate at the time of harvest; however, root respiration was higher in the anaerobic and alternating treatments. (Copyright (c) Amer. J. Bot. 71(10): 1424-1431. 1984.)