The Effects of Osmotic and Nutritional Variation 295 



tio 



20 30 AO 50 



OSMOTIC PRESSURE IN ATMOSPHERES 



%. SALINITY 



'\60 



|102 



Ftg. 5. Growth of Z. ewf/o at different temperatures on subsistence medium 

 plus sea water. No growth at 37 C. Compare with Figure 1. 



fact that it first appeared on media of various sea water con- 

 centrations. Glucose, glycerol, and erythritol all demonstrate it. 

 The osmotic gradient need not be produced by a metabolically 

 active substance, inasmuch as glycerol is effective as well as glu- 

 cose. The growth pattern is not dependent on the nutrient level, 

 though the organism must have enough to live on. Raising or 

 lowering the level of glucose, nitrogen source or calcium concen- 

 tration in the medium did not, in itself, alter the pattern. 



Substances which could bring out the Phoma pattern had 

 only one feature in common: they all produced osmotic gradients. 

 If the curves for every substance tested are plotted for one 

 temperature, the growth peak appears repeatedly in the same 

 range of osmotic values. For example, at 25 C, the fastest growth 

 for all substances occurred when the osmotic value of the medium 

 lay between about 10 and 25 Atm. At 30 C, the peaks all lay 

 between 30 and 40 Atm except in the case of glycerol which 



