On Water Exosmosis in Chaetomorpha Linum (Müll.) Kütz.

1. Chaetomorpha Linum (Mull.) Kiitz. was cultured in artificial seawater in the laboratory. 2. Cellulose, the main wall-substance, was isolated macrochemically by means of the method of Naylor and Russell-Wells (1934). 3. The potential milieu was investigated for ten successive concentrations of the triple-salt combinations of NaCl, CaCl2 and MgCl2 and plotted in triangular diagrams after macroscopic and after microscopic observation of the alga. A striking correspondence is found between these two sets of triangular diagrams. 4. The potential milieu appeared highly dependent upon total concentration. 5. A range of good conditions was found in the Ca-Mg combinations, although these salt-combinations do not occur in natural waters. 6. The seawater-point lay well out of the centre of the potential milieu. 7. Plasmolysis-phenomena were studied in saccharose-seawater solutions. 8. The wall in intact cells is much thinner than in cells with incipient or proceeding plasmolysis. 9. From a survey of the methods used in measuring changes in water-contents it appears that in the case of Chaetomorpha these methods are not applicable. 10. Two new methods especially adapted to the filamentous shape of Chaetomorpha are described; a. the refractometric method. b. the dilatometric method. 11. By means of the refractometric method the water-quantities passing through the wall into the surrounding liquid were determined. Four series of measurements were carried out, two at 15° C, one at ± 20° C. and one at 26° C. 12. With the dilatometric method the volume of the filament was measured directly after plasmolysis. 13. The swelling of the membrane was measured in intact cells as well as in pricked ones (“relaxed membranes”), in a range of saccharose-seawater solutions. 14. It was possible to calculate the volume of the filament after plasmolysis from the data obtained by means of the refractometric method and by microscopic measurement. 15- It proved to be impossible to explain quantitatively the differences between the calculated values and those obtained bij means of the dilatometric method. 16. By means of the refractometric and the dilatometric methods and microscopic measurements some data were obtained for the plasmolysis-phenomena in diluted and concentrated seawater.