36 



PHYSIOLOGY OF THE FUNGI 



In physiological studies dealing with high concentrations of nutrients, 

 it is important to distinguish between osmosis and osmotic pressure. 

 Osmosis is the transfer of water through a membrane permeable to water 



160 



120 



^80 



E 



40 



10 



20 



Degrees centigrade 



30 



40 



10 20 30 



Temperature in degrees centigrade 



Fig. 5. A, the effect of temperature on the dry weight of mycelium produced by 

 Glomerella cingulata after 5 days in 25 ml. of liquid glucose-asparagine medium. 

 (Drawn from the data of I. G. Bennett, 1951.) B, the effect of temperature on the 

 rate of linear growth of Neurospora crassa. (Courtesy of Ryan, Beadle, and Tatum, 

 Am. Jour. Botany 30 : 785, 1943.) 



but not to the solute molecules. In simple systems water passes from a 

 dilute to a more concentrated solution. Osmotic pressure is the force 

 necessary to restrain the movement of water from a dilute to a concen- 

 trated solution through a semipermeable membrane. The osmotic pres- 

 sure which a solution is capable of developing is a function of the number 



