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



bacterised peat ; Series V, Detmer's solution, with the addition of the 

 phosphotungstic acid fraction of bacterised peat. No experiments were made 

 with the silver fraction on account of the lack of available material at the 

 commencement of the experiment. 



Detmer's solution was the standard solution consisting of potassium 

 nitrate, 7 grm. ; dipotassium phosphate, T5 grm. ; magnesium sulphate, 

 1*5 grm. ; sodium chloride, To grm. ; calcium sulphate in excess (5 grm. were 

 nsed) ; ferric chloride solution, a few drops ; and distilled water, 3000 c.c. 

 This solution contained nitrogen, phosphorus, and potash, estimated as NH 3 , 

 P 2 5 , and K 2 0, in the proportion of 393, 204, and 1220 parts per million 

 respectively, the total concentration of salts being about 5500 parts per 

 million. 



The water extract of bacterised peat was prepared by leaching out, by 

 means of boiling distilled water, all soluble matter from a weighed quantity 

 of bacterised peat, and making up the liquid to a known volume. An aliquot 

 portion of this solution, containing the extract from \ grm. bacterised peat, 

 estimated on the dry weight, was added to each of the dishes containing 

 Detmer's solution in Series II. 



The water extract of bacterised peat, freed from humic acid, was prepared 

 by precipitating the humic acid from a water extract prepared as above, 

 by the requisite amount of a very dilute solution of calcium chloride, and 

 removing the calcium humate by filtration. An aliquot portion of this 

 liquid, representing the extract from \ grm. peat, was added to each of the 

 dishes in Series III. 



The alcoholic extract and the phosphotungstic fraction were obtained by 

 the methods described in the previous communication. The alcoholic extract 

 from 1 grm. of bacterised peat was added to each of the dishes in Series IV, 

 and the phosphotungstic fraction from 2| grm. to each dish in Series V. 



In order to ensure the use of uniform culture solutions, stock solutions 

 of all the required substances, sufficient to last throughout the whole of the 

 experiment, were prepared at the outset. The Detmer's culture solution was 

 prepared in a concentration of 100 times the strength required, and the 

 various organic extracts were prepared in concentrated solutions, to which a 

 little chloroform water was added to prevent bacterial action. The chloro- 

 form was removed by gentle evaporation on the water-bath each time the 

 liquids were required for use. 



The proportions of total substances added in the various series to the 

 5500 parts per million of mineral salts in the Detmer's solution are shown in 

 the Table below. 



