Intracellular Acidity in Valonia

The very large cells of the marine green alga Valonia macrophysa permit one to obtain several cubic centimeters of fluid from the central vacuole of a single cell (cf. Wodehouse, 1917), without involving appreciable alteration in the composition of the cell-sap through protoplasmic 'injury during the process of extraction (cf. Chambers, 1917). Estimations have been made of the acidity of this cell-sap. These measurements, although perhaps revealing no essentially new points of theoretic interest, are nevertheless valuable, since they bear so directly upon some questions regarding the reaction of the cell interior. The cell-sap of Valonia is much more acid than the sea water in which the plant is living. The reaction of the sap from fifty cells as obtained immediately after their removal from the sea was found to vary in individual cases from pH 5.0 to 6.7, the mode being at 6.0, the average 5.9. In thus possessing an acid internal medium the Valonia cells resemble those of some flowering plants containing natural indicators (Haas, 1916). Valonia grows in great masses at a depth of several feet beneath low-water level in certain mangrove "creeks," and also, less abundantly, among other seaweeds, on the reefs. The alkalinity of the sea water in the tidal creeks depends upon the state of the tide: at flood-tide, for example, in Fairyland Creek, the water most distant from the mouth of the creek was at pH = 8.2, while that half way toward the mouth of the creek was at 8.1, and in the adjacent regions of Great Sound, 8.07; at low-tide next morning, the alkalinity at the head of the creek was pH = 8.3. A similar rhythmic altera581