Growth o/Lemna minor in Mineral Culture Solutions. 493 



the successive ordmates. Upon joining up these points, two steadily rising 

 -curves are obtained for the numbers and weights, corresponding to an 

 ascending order of complexity in the fractions supplied. 



Detmer's Detmer Detmer Detmer Detmer 

 solution phosphotungstic Alcoholic Vkterextract Water 

 fraction extract free from extract 

 numic acid 



Fig. 4. 



It is of interest here to compare the effect of auximones in the 1915 

 experiments with that shown above. The only comparable figures are those 

 obtained with the phosphotungstic fraction for the first seven weeks of each 

 experiment, since no figures are available for the 8th week. The figures 

 for this period of the experiments shown in Table III give a percentage 

 increase in number over the control plants of 77"4, while the preceding year's 

 figures show an increase of 64 - 5 per cent, for the corresponding period. 

 Allowing for the variation in conditions of weather and environment it is 

 thus evident that there is a close agreement between the results obtained 

 during the two seasons. 



Experiments with Conductivity Water. 

 In view of the well-known fact that ordinary distilled water such as is 

 commonly used in the laboratory contains traces of toxic substances, it was 



