The lement concentrations of intracellular compartments of leaf cells of Egeria densa are estimated by X-ray microanalysis. Ultrathin frozen-dried sections are used in TEM mode. The concentrations of Na, Mg, P, Cl, K, and Ca are determined in the cell wall, cytoplasm and chloroplasts. The cell wall represents a Donnan free space with a negative fixed charge concentration of 360 mval/l water. The water fraction of the cytoplasm is between 85 and 90% and strikes the bounds of possibility of that method.