6U 



just allowed normal germination in a period of 18 hours. In 

 the first column are listed the substances dealt with. The 

 second column presents the concentrations in which the spores 

 are killed in 18 hours and fail to germinate later, aft^r 

 transfer to distilled water. Here, as in many other instan- 

 ces , the critical concentrations must not be regarded as 

 definite in the sense of the more exact physical sciences; 

 the concentrations employed in the experimental series were 

 frequently rather widely separated, and were this not the 

 case, the variability of the organism in its resistance to 

 toxic substances would render quite useless any attempt to 

 define such critical points with very great accuracy. In all 

 such work as the present, dealing with large nximbers of or- 

 ganisms, the internal conditions of the cells must be as im- 

 portant in determining reactions as are the external ones, 

 and we are as yet unable either to control or measure the 

 former excepting in a very general way. 



In the third column are found the concentrations 

 at which the different salts inhibit germination for at 

 least 18 hours. 'Vhen spores from these cultures were removed 

 from $he toxic solution and placed in water for a day they 

 geminated. The fourth column gives the maximum concentrat- 

 ion in which germination occurred. In all cases this growth 

 was abnormal, showing swellings, swollen tubes and other 

 unusual structures, such as are illustrated in figs. 1-6-. 



