12 BULLETIN 108, U, S, DEPARTMENT OF AGRICULTURE. 



These data show that salicylic aldehyde was harmful even in 

 nutrient solutions containing an excess of lime. The growth in each 

 culture with salicylic aldehyde was less than the corresponding cul- 

 ture which contained no salicylic aldehyde. The total growth of the 

 six control cultures was 17.89 grams against 13.40 grams for the six 

 salicylic aldehyde cultures. Putting the normal at 100, the salicylic 

 aldehyde cultures become 75, a reduction in growth of 25 per cent. 



In another test, involving a much larger number of cultures of 

 varying composition, essentially the same result was obtained. In 

 this case the growth was depressed 21 per cent as an average. 



In the previous experiment, involving a larger number of nutrient 

 solutions without calcium carbonate, growth was reduced 27 per cent 

 by salicylic aldehyde, used in the same concentration as in the experi- 

 ment with lime carbonate. 



The roots of the plants were not as much stunted by the salicylic 

 aldehyde in the presence of lime carbonate as they were in the experi- 

 ment when no lime carbonate was used. The tops, however, were 

 equally affected in the carbonate cultures. From these experiments 

 under alkaline conditions it is seen that the harmfulness of salicylic 

 aldehyde can in no wise be attributed to any slight acidity it may 

 possess. 



OCCURRENCE OF ALDEHYDES IN GARDEN AND FIELD SOILS. 



The discovery of salicylic aldehyde with the harmful properties 

 toward plants shown in the preceding section led to a study of the 

 extent to which material of this type is likely to be encountered in 

 soil investigations. In extending this study to many soils it was 

 not feasible to examine large quantities of each soil, so that it was not 

 possible to demonstrate clearly the identity of the aldehyde obtained, 

 but it was possible so to treat a sample of soil as to obtain the com- 

 pounds of an aldehyde nature contained therein, separated from com- 

 pounds having nonaldehyde properties. This aldehyde material was 

 tested as far as the quantity permitted for such reactions as are given 

 by salicylic aldehyde, namely, coloration with ferric chloride, and the 

 general aldehyde reaction with fuchsine reagent. In all cases the 

 aldehyde was subjected to the physiological test as to its effect on 

 plant growth, using wheat seedlings in the well-known manner. The 

 procedure employed in extracting the aldehyde material from the soil 

 and the manner of testing it was as follows : 



Twelve to sixteen pounds of soil were used in the examination for 

 aldehyde. The soil was extracted with 8 liters of a 3 per cent 

 solution of sodium hydroxide. The solution was stirred for 6 to 8 

 hours and, after settling, the liquid was poured off. The alkaline 

 extract was acidified with sulphuric acid and filtered from the so-called 

 humus precipitate. The acid filtrate was shaken out with several 



