Relation of water loss to moisture content of hydrophytes in a natural pond

Hydrophytes growing in natural ponds on the Coteau du Missouri in North Dakota have been studied. Previous studies in the same region showed how transpiration by hydrophytes could be separated from the total water loss from a natural pond, during the period that vegetation was growing in height, on the basis of a correlation between the height of vegetation and a mass‐transfer coefficient. It is shown that a similar separation can be made during the period of declining activity of the vegetation. A significant correlation was found between the ratio of moisture content of vegetation to its oven‐dry weight and the mass‐transfer coefficient. Weekly photographs on Ektachrome Infrared Aero film helped to confirm some of the phenomena observed.