THE VITAMINES IN THE VEGETABLE KINGDOM 71 



fertilizer was investigated. The results obtained in the fifth week 

 were as follows : 



Average number 

 of plants 



1. Control solution 27.0 



2. Extract of rotted leaves 64.6 



3. Extract of soil 64.4 



4. Extract of fermented peat 132.6 



It is evident that identical results were obtained with fertilizer 

 and with bacterized peat; indeed, fresh fertilizer was less active than 

 one in which marked bacterial decomposition had set in. Mocke- 

 ridge then found that nucleic acids and nucleotides predominated in 

 the less active extracts, while in the more active extracts, the amount 

 of free purine and pyrimidine bases was increased. Therefore, the 

 conclusion was made that the effect was brought about not by the 

 nucleic acids themselves, but by their decomposition products. 

 These conclusions are obviously not justified especially since the 

 investigations were not carried out with pure chemical products; 

 consequently the results could be only interpreted to indicate that 

 the substrate acted favorably on plant growth because of some 

 unknown changes that had taken place in the composition of 

 the substrate. Hydrolysis of the afore-mentioned nucleic acids 

 could well be thought of as a secondary occurrence without any 

 physiological significance. It is very likely that the growth-promot- 

 ing activity of peat and soil extracts is not due to the nucleic acid 

 decomposition products but to the presence of vitamines which are 

 carried down in the fractionation. Should it be established that in 

 the growth of plants, similar substances are involved as in the growth 

 of yeast, then it would be very improbable that they could be asso- 

 ciated with purine and pyrimidine derivatives. 



Miss Mockeridge's idea of the vitamine cycle, was that the nitrify- 

 ing bacteria furnish the green plants with the growth-promoting 

 substances which are used in the metabolism of the plants, partly 

 transformed into the vitamines already known to us, and which can 

 then be utilized by the animals. 



The investigations of Bottomley and Rosenheim have estab- 

 lished that higher plants also need a vitamine of the antiberiberi 

 type in their metabolism, and Bottomley expressed the idea that 

 this vitamine occurred in the plant through symbiosis with certain 

 bacteria. Whether this is the only vitamine that plants need, 



