26o 



Bulletin 275. 



S T E U 



DIL 



T J i\ 'SIL' E n 

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wr 



Vi ^ A'' 



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Fig. 71 — Rcprcscjitative tvhcat seedlings grown in extracts diluted and undiluted 



Reading from Icjt to right, the plants were grown in (/) diluted extract of steamed 

 soil; (2) undiluted extract of steamed soil; (j) undiluted extract of tmsteamed soil; 

 {4) diluted extract of unsteamed soil. 



extract of steamed soil. This is an indication, but probably not an 

 infallible one, of the presence of toxic substances. It does not seem 

 nnreasonable that such substances were formed in the transformations 

 of the organic matter under heat. Diluting the extract mitigated 

 but did not entirely remove the effect, as shown by the increased yield 



