47 



The extract ash ])rodiice(l neary twice as much growth 

 of j)eas as did the untreated extract; but lor sorghum, 

 little improvement was aliected by ashing. 



The results of this experiment appear to show that 

 the toxic body in this extract is organic, at least in 

 part. But special attention is called to the use of tap 

 water in this case. The unexpected results obtained 

 from the non-volatile part of the extract, and the ex- 

 tract ashed, both of which were made to volume with 

 tap water, warranted a careful examination of the lap 

 water used; and it w^as found to carry a very consider- 

 able quantity of calcium bicarbonate in solution. Since 

 the untreated extract was highly toxic, the toxic body 

 should have been found in either the volatile or the 

 non-volatile part; but in this case, both separates sup- 

 ported a very fair growth, quite in disagreement with 

 the results reported in Table III, where sorghum was 

 also used as the plant indicator. It was suggested that 

 the results obtained might be due to the bicarbonate 

 of calcium carried in the tap water, which served to 

 a certain extent as an antidote to the manganese in the 

 soil extract. 



In the effort to determine whether or not the salts 

 in the taj) water were responsible for the good root 

 and top growth in the non-volatile part, and in the 

 ashed part of the soil extract, another test was made, 

 using a soil extract containing manganese equivalent to 

 204 p. p. m. of manganese sulphate. Unfortunately, a 

 severe storm smashed a laboratory wdndow and blew 

 some of the plants from the containers, making it im- 

 possible to get the complete record. Notes on root and 

 top development had been made previous to the acci- 

 dent, however, and these are here given. 



Boiling the extract or heating it to 80''C., had little or 

 no effect on the toxicity. The volatile part supported 

 a good growth of roots, and a fair growth of tops. And, 

 in agreement with the results given in Table IV., the 

 non-volatile ])art made to volume with tap water pro- 

 duced a good growth of both roots and tops. On the 

 other hand, the non-volatile part made to volume with 

 distilled w^ater produced a fair amount of tops, but root 

 development was almost completely inhibited. 



This experiment was again repeated, with modifica- 

 tions, using a soil extract containing 60 p. p. m. of Mn. 

 The results are shown in Table V. 



