1913-] SCHREIXER— TOXIC SOIL SUBSTANCES. 425 



cooperation with Professor Floyd, of the Florida Experiment Sta- 

 tion, to see whether they are responsible for this disease. Like the 

 apple orchard experiment this work is still in progress and not suffi- 

 ciently well advanced to discuss its practical significance but it serves 

 to show the application of this type of biochemical investigation to 

 certain great economic problems which confront many agricultural 

 industries. Another of these harmful soil constituents is the pleas- 

 ant smelling vanillin, a constituent of the vanilla bean, but also of 

 many other plants, as shown in this and many other laboratories, 

 and a compound which is somewhat harmful to wheat seed- 

 lings in solution cultures, chemically an aldehyde and thus a 

 reducing agent capable of being oxidized and having its harmful 

 properties reduced by such oxidizing fertilizers as nitrates. The 

 properties of vanillin in regard to plant growth and its effect on 

 root oxidation and the intluence of fertilizer salts on its action, were 

 determined on wheat in our laboratories several years ago in antici- 

 pation of the day when it would be found as a soil constituent. 

 What is true in this respect of vanillin is also true of a number of 

 other compounds but it is also equally true that some of the soil con- 

 stituents isolated were not even remotely suspected of ever being 

 found in soils, and in fact some of them have been previously only 

 known as products of the chemist's laboratory, for instance, the 

 saccharic acid, a laboratory oxidation product of sugars, or the tri- 

 thiobenzaldehyde, previously only known as a sulphur substitution 

 product of the laboratory. 



While the subject of my talk limits me chiefly to a discussion of 

 th.e soil substances which we have found to be harmful in our experi- 

 ments, I must not omit in passing to speak of the many beneficial 

 substances which have been discovered in soils as the result of these 

 investigations, and which even more than the toxic substances, make 

 clear the parallelism existing between the biochemistry of the soil 

 and the biochemistry of the animal, because some of the compounds 

 involved are absolutely identical. Among this list of beneficial soil 

 compounds you will recognize common products of animal metabo- 

 lism and digestive processes such as creatinine, found in the urine ; 

 histidine, arginine, lysine, products of protein digestion; xanthine, 



