OSMOTIC CONCENTRATION OF SAP. 2O3 



in the winter of 1915 and in the Everglades region of southern 

 Florida in the winter of 1916. 



The specific problem attacked is that of the osmotic concen- 

 tration of the tissue fluids. 



It is quite natural that zoologists should have led in the inves- 

 tigation of the relationship between the concentration of the 

 tissue fluids and of that of the medium surrounding the organism. 

 They have had at their disposal a wealth of forms exhibiting the 

 widest possible range of organization, living in a medium which 

 while showing a considerable range in concentration is neverthe- 

 less relatively constant over large areas, and opposes no ob- 

 stacles to the easy extraction of samples of fluids (blood) for 

 comparison with the medium. Among those who have contri- 

 buted to the literature of this field may be mentioned Botazzi, 

 Fredericq, Garry, Macallum, Green, Dakin, Mosso, Dekhuyzen, 

 Scott, and others. The subject is discussed by R. Hober in his 

 "Physikalische Chemie der Zelle und der Gewebe." Just as 

 these pages were being prepared for the printer a summary by 

 Scott ('16) of the data available for the depression of the freezing 

 point of the blood of representatives of the various phyla of the 

 animal kingdom, with the values obtained for the water in which 

 the individuals were taken, appeared. 



The problem of the osmotic concentration of the cell sap of 

 the plant organism in relation to its medium has been rather 

 extensively studied by a number of workers on the algae and fungi. 

 In recent years a number of investigations have also been carried 

 out on the higher plants, both in the laboratory and in the field. 

 These botanical studies need not be reviewed here. 



It is perhaps clear that a study of arborescent plants growing 

 in the saline substratum of the tropical coast has certain points 

 of interest over that of the investigation of algae or other sub- 

 merged organisms. Not only is there the factor of the osmotic 

 pull necessary in water ascent but there is the possibility of the 

 increase in osmotic concentration of the foliar tissue fluids by 

 the retention in solution (and hence in an osmotically active 

 condition) of the salts absorbed from the concentrated substratum 

 and left in the leaf tissue by the rapid transpiration incident to 

 tropical temperature, insolation and air movements. 



