120 



Mycologia 



soil, the heated-soil extract was reduced to almost exactly the 

 same condition as the extract of the same soil before heating. 



(b) Qualitative 



We next undertook to investigate the nature of the substances 

 that seemed to make heated-soil extracts favorable culture media 

 for Pyronema and other fungi. The pungent odor of the extracts 

 of heated-soil together with the pronounced acidity towards litmus 

 suggested acids, while the dark color and caramel odor suggested 

 carbohydrates or their decomposition products. The following 

 tests were made on heated-soil extracts before being evaporated: 



Litmus paper — red. 



Lead acetate — brownish precipitate. 



Silver nitrate — slight precipitate (not soluble in ammonia). 



Barium chloride — slight precipitate. 



Alcohol — slight precipitate. 



Calcium hydroxide — slight precipitate. 



Ether — does not dissolve color of solution. 



Molisch test — positive. 



This same extract when evaporated to one fiftieth its original 

 bulk showed the same reactions in every case except that they 

 were far more pronounced. This concentrated extract also 

 caused a strong reduction of Fehling solution while the blanks 

 were negative. All of the above tests were repeated many times 

 and the results were practically always in accord with those 

 described above. 



When unheated-soil extracts were tested in exactly the same 

 manner, the acidity was slight as shown by litmus, barium 

 chloride gave a slight precipitate (owing to sulphates), and silver 

 nitrate also gave a slight precipitate wholly soluble in ammonium 

 hydroxide (probably owing to chlorides), while all the other tests 

 were negative. 



From the qualitative tests just described we are inclined to 

 believe that upon heating to about i6o° to i8o° C, the organic 

 matter in the soil undergoes some deep-seated changes probably 

 oxidative in nature, favored by the high temperatures, which 

 give us the water-soluble products of an acid character producing 

 the dark-colored solutions. The acidity of heated-soil extracts 



