70 THE VITAMINES 



Bottomley's laboratory, Mockeridge (186) studied the effect of 

 extracts of bacterized peat upon nitrifying bacteria of the soil (Bacil- 

 lus radicicola and Azotobacter chroococcum) . The results are apparent 

 from the accompanying table, in which the milligrams of fixed 

 nitrogen are given. 



1. Nutritive medium alone 2.6 



2. Nutritive medium plus watery extract of ordinary peat 1.9 



3. Nutritive medium plus watery extract of fermented peat 7.7 



4. Alcoholic extract of fermented peat 6.5 



5. Phosphotungstic acid precipitate of No. 4 5.6 



6. Silver fraction of No. 5 6.5 



We may see from these results that the above bacteria, having 

 synthetic ability to assimilate nitrogen from the air, are nevertheless 

 influenced by vitamines. While the vitamine action was favorable 

 to the fixation of nitrogen, the effect upon denitrification was reduced, 

 and the formation of ammonia was uninfluenced. The investigations 

 were then applied to other soil bacteria and it was found, as a rule, 

 that the growth of the nitrifying bacteria is activated by vitamines, 

 while that of the putrefaction, denitrification, and ammonia forming 

 bacteria is not affected. Those bacteria which have the power of 

 decomposing organic matter should in fact have no need for vitamines 

 or else should be able to synthesize them. These two great classes 

 of bacteria, one that begins the nitrogen cycle and the other that ends 

 it, differ from each other entirely in their metabolism if Mockeridge 

 is correct. 



It must be especially emphasized that Bottomley and his school 

 always moved further and further away from the importance of the 

 vitamines for plant growth, and ascribed this remarkable action to 

 the nucleic acid derivatives. These conclusions followed in the paths 

 which Schreiner and Skinner (187) and their co-workers laid out 

 for the action of nucleic acid derivatives on plant growth. These 

 investigators isolated from the soil some purine and pyrimidine 

 derivatives and tested their activity. They showed that xanthine 

 could increase the weight of wheat sprouts kept in water about 21 

 per cent. Similar experiments were made by Macalister (188) with 

 allantoine and by Coppin (189) with other analogous substances. 

 Recently, Miss Mockeridge (190), experimenting with Lemna major, 

 showed that green plants need an addition of certain other sub- 

 stances to continue to live. In this series, the influence of natural 



