The relation of soil aeration to water absorption by the roots of intact transpiring plants has been considered by a number of workers whose extensive writings have been the subject of brief reviews (2, 12, 19, 21). While a great variety of results and some conflicting data are reported, there is a general agreement that poor aeration decreases the rate of water absorption by plants and may produce wilting when transpiration is sufficiently rapid. In their reviews, Kramer (12) and Compton (2) suggest that inadequate aeration reduces water absorption as a result either of (1) a decreased permeability of the roots or (2) a decreased absorption surface as a result of the death of rootlets and of the cessation of root growth. Thus aeration may either directly influence the rate of water influx by affecting cellular activities, which control cell permeability, or indirectly affect water absorption as a result of aeration-induced secondary factors. Separation of the direct and indirect effects of aeration is difficult. The introduction of deficient aeration conditions will, among other changes, produce adjustments in the solute status and metabolic activity of the root cells, affect root growth, and result in the death of some, and ultimately all, of the root tissue. Though these secondary factors cannot be entirely avoided in studies using intact plants, their influence can be minimized by short-time experiments. The differences in root anatomy of water-culture and soil-grown roots (17) suggest the desirability of carrying out aeration studies with plants in soil whose moisture content is allowed to vary over the usual field range, i.e., approximately from field capacity to the permanent wilting percentage. However, the use of soil-grown plants in aeration experiments requires that careful attention be given to the effectiveness of aeration control obtained.