25 



of the high osmotic pressure of the medium. To obtain evi- 

 dence on this point, the germination of the spores was 

 tested in various concentrations of cane sugar. A C.2m stock 

 solution of this was made up from granulated sugar which 

 had been pulverized and then desiccated; the different con- 

 centrations used in the cult;ires were prepared from this. 

 The spores germinated normally in 1.4m concentration or 

 below; considerable germination in the form of local swell- 

 ings (see fig. i ) was found in a 1.6m solution, and no 

 germination occurred in 1.8m concentration. The concentra- 

 tion of cane sugar which just inhibits germination lies 

 then betwesn 1.6 and 1.8 molecular. 



It will be observed that a 1.6m solution of sucrose 

 exerts about the same effect upon the germination of these 

 Gloeosporiura spores as do C.6m, C.5m and molecular solutions 

 of calci^lm, magnesium and potassium nitrates respectively. 

 Calculations-^^ of the osmotic pressures of these four 

 12. Morse, H. N., and Holland, W. W., The osmotic pressure 

 of cane sugar solutions at 25°. Am. Ghem. Journ. 41:1-19. 19Ca 

 The osmotic pressure of molecular cane sugar was measured dir- 

 ectly by these writers and the osmotic pressure of 1.6m cane 

 sugar as given above was calculated from their tables. It is 

 probably low as they found that the ratio of observed to cal- 

 culated osmotic pressure increased with the concentration. 

 For gas pressure formula by which the osmotic pressxire of the 

 thr« electrolytes was calculated see Landalt and Bernstein, R., 

 Physikalische Chemische Tabellen. 3rd auflage Berlin 'CS, p. 24. 



