242 



Prof. W. B. Bottomley. 



entirely precipitated by pliosphotungstic acid from an aqueous solution of the 

 dry residue from the alcoholic extract of rice polishings, and Hopkins* also 

 states that he obtained the best results upon growing rats with the fraction 

 from the crude phosphotungstic acid precipitate of protein-free milk. Conse- 

 quently an experiment was made to determine how far the phosphotungstic 

 acid fraction of the bacterised peat extract was effective in stimulating plant 

 growth. The bacterised peat was extracted with absolute alcohol as described 

 above, and the alcohol evaporated off in vacuo. The residue was taken up in 

 water, filtered, and to the filtrate sulphuric acid was added, until the concen- 

 tration of the latter reached 5 per cent. A slight precipitate of humic acid 

 was filtered off, -and to the filtrate an excess of 30-per-cent. solution of 

 phosphotungstic acid was added. The whole was then left to stand overnight, 

 when the liquid was decanted off through a filter, the precipitate repeatedly 

 washed with a 5-per-cent. solution of sulphuric acid, and finally decomposed 

 with an excess of baryta. The liquid was filtered off from the precipitate of 

 barium phosphotungstate, and the filtrate, freed from the last traces of baryta 

 by means of a very dilute solution of sulphuric acid, was evaporated to 

 dryness in vacuo. From 7 kgrm. of bacterised peat the amount of dry 

 substance obtained from the phosphotungstic acid fraction amounted to 

 12-0096 grm., and since this was made up for experimental purposes into a 

 solution containing the fraction from 10 grm. of peat per litre, the proportion 

 of the dry phosphotungstic acid fraction in the final solution employed 

 consisted of 17 parts per million. This fraction was tested upon wheat- 

 seedlings in conjunction with Detmer's complete food solution. Ten seeds 

 were germinated in clean sand in each of nine pots, which were arranged in 

 three series of three pots each. Series I was treated with a complete food 

 solution, Series II with complete food plus alcoholic extract from 10 grm. of 

 peat per litre of solution, and Series III with complete food plus phospho- 

 tungstic fraction from 10 grm. of peat per litre of solution. The food solution 

 employed contained nitrogen, phosphorus and potash, estimated as NH 3 , 

 P 2 5 , and K 2 in the proportion of 400, 200, and 1220 parts per million 

 respectively, so that in addition Series III had 17 parts per million of 

 dry substance obtained from the phosphotungstic fraction. Each pot was 

 treated with 100 c.c. of its solution one week after sowing the seed, and the 

 treatment repeated once weekly for five weeks, at the end of which period 

 the plants were uprooted, washed, dried, and weighed. The results were as 

 follows : — 



* Hopkins, ' Brit. Med. Journ.,' vol. 2, p. 463 (1913). 



