1913.J SCHREINER— TOXIC SOIL SUBSTANCES. 423 



acid, dihydroxystearic acid, oxalic acid, salicylic aldehyde and va- 

 nillin as having been found in unproductive soils should receive 

 special mention. The first of these is only moderately toxic and 

 has not been exhaustively studied, but is interesting in showing that 

 nitrogen in such a compound is not only not available to plants, but 

 that the compound containing it is unfavorable to plant develop- 

 ment. The dihydroxystearic acid, on the other hand, has been more 

 thoroughly studied and has been encountered in soils from many 

 parts of the United States. It is a strong inhibitor of the normal 

 processes of plant metabolism and destroys almost entirely the 

 normal oxidizing power of plant roots, thus inhibiting root devel- 

 opment and the power of absorption of mineral plant foods by the 

 roots, even if present in the most available forms. Salicylic alde- 

 hyde is even more toxic than the dihydroxystearic acid and like 

 salicylic acid it is a strong antiseptic, inhibiting the action of bac- 

 teria. This salicylic aldehyde was first discovered in a soil from the 

 historic Mt. Vernon estate of George Washington, in the rose garden 

 near the box hedge laid out by our first President. The remarkable 

 fact in connection with this soil was that it contained a large amount 

 of mannite, as much as 500 lbs. per acre. Although this is the only 

 soil in which it has been found, the remarkable part was not in its 

 being found there, for it can readily be produced by certain soil 

 fungi, but rather that it should persist in the soil, when it is such 

 an excellent medium for the development of bacteria. This sugar 

 alcohol appeared to have no unfavorable efifect on plants when it 

 was tested in our greenhouse, but we were never able to make a good 

 test because of the fact that the mannite solutions with the added 

 fertilizer salts were such good media for the development of bac- 

 teria. The simultaneous presence of the salicylic aldehyde in the 

 soil, and the fact that the latter was poisonous to higher plants, sug- 

 gested therefore that the mannite in the soil was protected by the 

 antiseptic action of the salicylic aldehyde. Experiments confirmed 

 the antiseptic action of the salicylic aldehyde in preventing the 

 decomposition of the above mannite solutions and the occurrence of 

 the large quantity of mannite in this soil seems thereby explained. 

 This case is particularly interesting as showing that soil compounds 



