67 



added to the nutritive solution in a dilution of 0.35 in 1,000,000. 

 Bottomley's results were soon confirmed by others (175). The sub- 

 stances influencing plant growth were called "auximones" by Bot- 

 tomley, who also described a method for their detection (176). This 

 method possesses certain advantages as against the use of higher 

 plants, and consists in an extraction of fermented peat, and precipita- 

 tion of the resulting extract with phosphotungstic acid. If this 

 extract is added to a culture of nitrifying bacteria and the whole 

 placed in an incubator at 26C., a scum is formed on the surface 

 after 24 to 36 hours, and no nitrates are found in the solution. On 

 the contrary, without the addition of vitamine, the scum does not 

 appear and the nitrification proceeds rapidly instead. This method 

 seems to be specific for the vitamines, since no such effect has been 

 recorded after the addition of cane sugar, maltose, asparagine, 

 peptone, leucine, tyrosine and hordeine. The microorganism isolated 

 from this scum, similar to the nitrifying and sulphur- and iron- 

 assimilating bacteria, may grow without the addition of organic 

 carbon combinations. Originally, Bottomley was of the opinion that 

 the auximones differed from the vitamines in that the. former were 

 heat resistant. We believe, however, that a successful classification 

 cannot be built up on such differentiations. Chittenden (177) 

 repeated these flower-pot experiments in which the ratio of the 

 bacterized peat to the required amount of soil was very high, and 

 therefore was also able to produce an acceleration of growth. When 

 this method of experimentation was applied to greatly extended 

 soil experiments, the results were not so significant; the greatest 

 success was obtained when the rainfall was large. Bottomley (178) 

 himself repeated his first experiment more carefully. For this 

 purpose he used a type of lentil (Lemna minor) that could live in 

 water; this was cultivated on Detmer's nutritive solution, of which 

 the only source of nitrogen was potassium nitrate. This plant could 

 not live only upon inorganic constituents; it gradually became 

 weaker, and presented an abnormal appearance. Bottomley then 

 added to the nutritive solution various extracts prepared from 

 fermented peat. From the results recorded in the table below, only 

 one conclusion may be drawn that the influence of these extracts 

 was due not only to the presence of certain necessary building stones 

 therein, but also to the presence of vitamines. These experiments 

 were then repeated by Bottomley (179) with other water-plants like 

 Selvinia natans, Azolla filiculoides and Limnobium stoloniferum, 

 with the same results. 



