The Effects of Osmotic and Nutritional Variation 293 



70 



60- 



50- 



40 



I 30 

 < 



> 



O 20 



_j 



o 



10 



25' - SEA WATER 



IP 



OSMOTIC PRESSURE IN ATMOSPHERES 

 20 30 40 50 60 



tie 



to.l7 



¥r^ 



'25 



'34 

 '^0.95 



T. 



i; 



'55%= SALINITY '80 '102 



^1.38 I74 MOLARITV- GLUCOSE 



Fig. 3. Growth of Z. ewf/a at 25 and 30 C on basic medium plus glucose 

 compared with that on basic medium plus sea water, with osmotic pres- 

 sures of the two made equal. 



of 0.5 per cent, colonies grew at the same rate, regardless of the 

 amount of yeast extract available. At 30 C, however, little or 

 no growth occurred on media which contained more than 0.1 

 per cent yeast extract. This was not a pH effect, inasmuch as 

 the pH of all media remained between 5 and 6. 



Total growth on a subsistence medium naturally was less 

 than on a richer nutrient, and the optiminn temperature for 

 growth, regardless of solute content, was reduced to about 20 

 C. Aside from these effects, however, the relation between 

 increasing temperature and increasing salinity optima on sub- 



