68 LON A. HAWKINS 



respectively. Calculations 16 of the osmotic pressures of these four solu- 

 tions give 51.36, 29.13, 26.00 and 39.31 atmospheres, respectively, from 

 which numbers it becomes obvious that the osmotic concentration of the 

 sugar solution was much greater than that of the other three. It is there- 

 fore suggested that, unless the wall and protoplasm of the spores here 

 employed be readily permeable to cane sugar (which seems highly improb- 

 able), the inhibiting effects observed with the salt solutions are not to be 

 related primarily to their osmotic properties. 



The relatively high osmotic pressure existing within the spores here 

 dealt with, as indicated by the data just given, renders it unnecessary to 

 consider osmotic pressure as a factor in bringing about the modifications 

 and inhibitions of germination which are next to be considered ; the con- 

 centrations of the various salt solutions employed were always far too 

 low to produce any removal of water from the cells. Similarly, the 

 toxicity of calcium, magnesium and potassium nitrates is so very slight 

 as not to require any consideration in connection with the combinations of 

 these salts with those of the heavy metals ; in these combinations the 

 salts of the lighter metals have not here been used in concentrations higher 

 than o.im. 



The influence of the nitrates of calcium, magnesium and potassium upon 

 the toxicity of salts of the heavy metals will now receive attention. 



Copper. 



As was to be expected, the effect of Cu(NO 3 ) 2 upon the germination of 

 these spores was found to be widely different from that of Ca(NO 3 ) 2 . No 

 germination was ever found in concentrations of the copper salt alone 

 higher than 0.00006111, and it was only in an occasional culture that one 

 or two spores were observed producing local swellings with that concen- 

 tration. Local swellings of the spore walls and swollen tubes were fre- 

 quently found with 0.00004111 and with o.oooo26m concentration, the next 

 lower one which was here used; with 0.00002111 solution of Cu(NO 3 ) 2 

 germination was about as in distilled water. 



Copper nitrate was combined with Ca(NO 3 ) 2 , at several concentrations 

 of the copper salt well above that at which the latter was non-toxic when 

 used alone. In a series of combinations of o.oooim Cu(NO 3 ) 2 with dif- 



18 Morse, H. N., and Holland, W. W., The osmotic pressure of cane sugar solutions at 25. Amer. 

 Chem. Jour. 41: I-IQ. IQOQ. The osmotic pressure of molecular cane sutfar was measured directly by 

 these writers and the osmotic pressure of 1.6 m. cane sugar as given above has been calculated from their 

 tables. The result is probably low, for they found that the ratio of observed to calculated osmotic pres- 

 sure increases with the concentration. For the gas pressure formula, by which the osmotic pressure 

 of the two electrolytes is calculated, see Landolt, H., Bornstein, R., and Meyerhoffer, W., Physikalische- 

 chemische Tabellen, 3te Aufllaije. Berlin. 1005; page 24. 



