The Effects of Osmotic and Nutritional Variation 289 



tion that the osmotic values of their sokitions are the same as 

 those of equimolar gkicose solutions. 



Osmotic value changes clue to temperature changes would 

 never have exceeded 5 per cent over the range of temperatures 

 used. Because of this, plus the fact that the measurement of 

 colony diameters suffers as great or greater error, temperature 

 corrections have not been included. Even with temperature ad- 

 justment, however, no great differences in the curves result. 



Because calcium is a normal constituent of sea water, and 

 because its presence is known to affect plasma membranes, its 

 concentration was considered as a possible factor in the Phoma 

 pattern. A basic medium containing the calcium in the 0.1 per 

 cent yeast extract or present as contamination was prepared with 

 solutions to which were added 0, 25, 50, 100, 250, 500 and 1000 

 parts per million of calcium, solidified with specially purified 

 Oxoid lonagar and poured into plastic petri dishes. Cultures were 

 incubated at 25 C ond 30 C. 



Various concentrations of yeast extract, peptone, and casa- 

 mino acids were incoi-porated into media in order to determine 

 whether certain nutrient factors might affect the Phojna pattern. 

 To the basic medium, solidified with 0.85 per cent Oxoid lon- 

 agar, we added Difco yeast extract in concentrations of per 

 cent, 0.1 per cent, 0.2 per cent, 0.4 per cent, 1.6 per cent, 3.2 

 per cent, and 5.0 per cent. Peptone and Difco casamino acids 

 were each made up in the same way in concentrations of per 

 cent, 0.05 per cent, 0.1 per cent, 0.2 per cent, 0.4 per cent, 0.8 

 per cent, and 1.6 per cent. These three runs were incubated 

 at only two temperatures, 25 C and 30 C, because these temper- 

 atures were known from previous experiments to be instructive. 



A subsistence nutrient medium was worked out to study 

 the effect of limited food supplv on the Phoma pattern and was 

 arrived at by measuring the growth of the fungus on a number 

 of media which contained salts and agar in the usual amounts, 

 and all possible combinations of the following percentages of 

 yeast extract and of glucose: Yeast Extract: per cent, 0.0125 

 per cent, 0.025 per cent, 0.05 per cent; Glucose: per cent, 0.0125 

 per cent, 0.025 per cent, 0.05 per cent, 0.1 per cent, 0.25 per cent. 

 Since 25 C is generally the optimum temperature for growth of 



