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 
