108 Bacterial Test for Plant Food Accessories (Auximones). 



extract from 50 grm. of fresh manure. It would thus appear that the 

 quantity of auxitnone present increases with the progressive decomposition of 

 the organic matter of the manure ; although the relatively small amount even 

 in the two-year-old rotted manure is apparent, when it is stated that a better 

 formation of scum was obtained with the fraction from -i- grm. of bacterised 

 peat than with 10 grm. of the manure. 



An unexpected source of plant auximones has been discovered in the root 

 nodules of leguminous plants. A quantity of root nodules from bean plants 

 were collected, and the phosphotungstic fraction obtained from them in the 

 usual way. The roots which bore the nodules were also extracted separately. 

 On investigation it was found that a very thin film was obtained when 

 nitrifying solutions containing the phosphotungstic fractions of ^ grm. of 

 roots and nodules respectively were inoculated with the scum-forming 

 organism. Liquids containing grm. gave a fair growth, and those 

 containing jLj- grm. a good growth, the extract from nodules giving a slightly 

 better growth than that from the roots in each case. A similar fraction was 

 obtained of the roots of beans which had been grown in sterilised sand and 

 which had formed no nodules, and no growth at all could be obtained upon 

 nitrifying solutions to which had been added the extract from grm. of 

 such roots. 



Some further interesting, points may be noted in connection with this 

 research. The organisms which form the scum require no organic carbon for 

 their growth, and are similar to the nitrifying organisms and sulphur and 

 iron bacteria in that they can assimilate atmospheric carbon dioxide by the 

 process of chemosynthesis. Further they cannot live on nitrates, but must 

 obtain their nitrogen from an ammonium salt. 



The plant auximones so far investigated differ in one important respect 

 from those concerned with animal nutrition in that they are not destroyed by 

 heating. A phosphotungstic extract from bacterised peat gave a thick scum 

 after being heated in an autoclave at 134° C. for half an hour. 



Hitherto lack of knowledge of the nature of plant auximones has retarded 

 research, but it is hoped that, just as the investigation of "deficiency" 

 diseases was promoted by Eykman's* production of polyneuritis in birds, and 

 the inducement of scurvy in guinea-pigs by Furstf, the discovery of a 

 bacterial test will facilitate an examination of the occurrence, nature, and 

 composition of plant auximones. 



* Eykman, ' Virehow's Arch.,' vol. 148, p. 523 (1897). 



t Fiirst, ' Verh. des 6 Nord. Kongress f. Inn. Med.,' p. 342 (1909). 



