1. In highly hypertonic solutions of sea water the rate of respiration of Laminaria agardhii is rapidly reduced.
2. In highly hypotonic solutions the rate of respiration of Laminaria agardhii is reduced somewhat less rapidly than in the case of hypertonic solutions.
3. Hypertonic solutions of NaCl, CaCl2, and of mixtures of NaCl, and CaCl2 in the proportion of 50:1, all caused a decrease in the rate of respiration of wheat seedlings.