424 SCHREINER— TOXIC SOIL SUBSTANCES. [April i8, 



affect the lower life of the soil as well as the higher plant life, and 

 through these the entire biochemical processes, and furthermore that 

 even if a compound like mannite be not toxic in itself, its very pres- 

 ence points to the fact that the soil is functioning abnormally, much 

 as the presence of sugar or albumen in the urine, in themselves harm- 

 less, point to the fact that something is decidedly abnormal with the 

 metabolism of the individual excreting them. The occurrence of 

 certain compounds in soils likewise becomes a great agent in the 

 diagnosis of soil troubles. The occurrence of the dihydroxystearic 

 acid is a not uncertain indication of low and sluggish oxidation in 

 the soil, whatever may be the cause that has brought this about, be it 

 poor drainage, acidity, poor physical management of the soil or 

 other soil abuse. 



The poisonous oxalic acid has been encountered in only one in- 

 stance thus far, and that in a soil containing much calcium carbo- 

 nate. The amount, however, was so extremely large, nearly four 

 tons of calcium oxalate per acre, that it is thought to play some part, 

 even as the insoluble oxalate, in the peculiar failure of apple orchards 

 in this soil. Experiments in greenhouse and orchard are still under 

 way to determine these facts and I mention this case here only to 

 point out the application of this type of investigation to problems 

 where other means fail to diagnose the trouble. Another applica- 

 tion of such work is in diagnosing the soil trouble which brings 

 about the mysterious disease of the orange tree and fruit known as 

 dieback with which growers have struggled for years with annual 

 loss of thousands of dollars and which scientists now consider as a 

 physiological disease, that is, one not caused by any pathological 

 organisms extraneous to the plant itself. All facts point to the soil 

 condition as the cause, but so inexplicable has been its behavior in 

 respect to the soil that all ordinary means of chemical investigation 

 have failed to lay bare the cause or causes. Typical dieback soils 

 from Florida are now under investigation in our laboratories at 

 Washington to determine in them such organic constituents as are 

 possible by the methods so far developed. This work is meeting 

 with success and a number of compounds have been isolated and 

 these will be studied in regard to their effect on orange trees in 



