488 Prof. W. B. Bottomley. Effects of Auximones on 



The total number of plants each week, and their dry weight for the 3rd and 

 succeeding weeks, are shown in the Table on pp. 48(3-7, the numbers repre- 

 senting, after the 2nd week, not those which were actually in the dishes, but 

 the numbers which would have resulted from the multiplication of the 

 original 20 had the dishes used been sufficiently large to obviate the need 

 for halving and quartering. The dry weights also correspond to the weights 

 of the complete sets whose numbers are given, and not to the fractions of the 

 whole sets which were weighed each week. By the end of the 6th week, the 

 labour involved in counting, halving, and estimating the dry weight of the 

 plants in the 50 dishes had become so great that it was impossible to 

 continue the whole of the work further. The experiment was carried on, 

 however, for another two weeks, with the object of recording only the 

 numbers of the plants in the various series. 



It is evident from the above figures that all the additions to Detmer's 

 solution have a beneficial effect on the growth of the Lemna minor in water 

 culture, and that there is a progressive beneficial effect both in number and 

 weight as the amount of added substances is increased. The most striking 

 results are shown in Series II with the complete extract of bacterised peat, 

 which in six weeks increased the numbers by 20 times (6723 : 326), and 

 the weights by 62 times (1103 : 17'6), those in Detmer's solution. As the 

 additions made consisted chiefly of organic substances, the conclusion appears 

 to be justified that it is the presence of organic matter which is responsible 

 for the results obtained, for it is difficult to understand how such increases 

 could have been brought about by the addition of inorganic nutrients only, 

 since the maximum proportions of nitrogen, phosphorus and potash added in 

 Series II amounted to only 4 - 8, l - 8 and 004 per cent, respectively of those 

 already present in Detmer's solution. 



The numbers obtained during the first six weeks are shown graphically 

 below, together with a diagrammatic representation of the maximum per- 

 centage addition of nitrogen, phosphorus and potash to the quantities 

 present in Detmer's solution. « 



A photograph of the whole set of 50 dishes, taken during the 6th week, 

 is shown on Plate 21. 



A comparison between the relative numbers and weights of plants in all 

 the series is more readily obtained by putting the average number and weight 

 of plants in Series I at 100 for each week, and ascertaining the corresponding 

 figures, which show the percentage of increase, for the other series. These 

 are shown in the Table below. 



