22 STUDIES ON RESPmATION. IX 



by a rise above normal, while still other experiments gave only normal 

 respiration. 



The writer believes that these results are due to two factors acting 

 on the fungus. One is the specific chemical action of NaCl which 

 tends to stimulate, while the other, the osmotic pressure of the NaCl, 

 tends to decrease the respiration. As is well known the abstraction 

 of water from tissues lowers the rate of respiration. The fact that 

 sometimes one factor prevails, and sometimes the other is probably 

 due to physiological differences in the fungus. 



Experiments with 2m NaCl show a large initial decrease followed 

 by an increase of about 10 per cent. This is also found with 1m but 

 is not so pronounced. The explanation of this fact may be that at 

 first rapid withdrawal of water occurs, but as the salt penetrates and 

 osmotic pressure within the cell increases, water is taken up, causing 

 a rise in respiration. This supposition is further strengthened by 

 experiments with 1.25m CaCl2,* which showed a large initial decrease, 

 not followed by an increase in respiration, but by a slow steady de- 

 crease which might be expected if CaCl2 does not penetrate readily. 

 Osterhout^ in his experiments on Laminaria showed that NaCl in- 

 creases the permeabihty, while CaCl2 at first decreases it. 



Only one concentration of CaCl2 was used with dextrose, but 

 several more concentrations without dextrose were employed. The 

 concentration used with dextrose was 0.5m. This caused an increase 

 in the respiration, giving a curve with rounded apex as shown in Fig. 

 3, Curve B. Concentrations used without dextrose were 0.3125m, 

 0.625m, and 1.25m. The first two caused a rise, while the last one only 

 a decrease in respiration. 



At this point it may be of interest to note that the effect of the salt 

 seemed to be more pronounced when dextrose was absent than when 

 it was present. This was especially the case with CaCl2. Kosinski 

 found that Aspergillus niger does not store up raw food material, and 

 that as soon as it is taken out of a solution containing nutrient material 

 it is in a starving condition. ^° He states that when this happens 



« This concentration of CaCU has approximately the same osmotic pressure as 

 2m NaCl. 



'Osterhout, W. J. V., Science, 1911, xxxiv, 187; 1912, xxxv, 112. 

 ^° In the writer's experiments the rate of respiration began to decrease about 30 

 minutes after transfer from nutrient solution to distilled water. 



