45 



A study ol' Tabic III along with the photograph on 

 Plate I, lig. 2, shows that by far the best growth was ob- 

 tained from the solution that had been precii)ilaled 

 with caustic soda, Avith the carbon black treated solu- 

 tion ranking second. The effect ol" carbon black was 

 much more pronounced on toj) than on root develoj)- 

 ment. The dui)licatcs in this culture failed to agree, one 

 making twice as much root as the other. The effect 

 of sej)araling the extract into volatile and non-vola lib- 

 parts is best seen in the photograph, since the root 

 weight fails to give a correct idea of the toxicity of the 

 two separates. In such cases as this, it has been found 

 tliat the short, stumpy roots developed are very woody, 

 and are much heavier than is indicated by their ap- 

 pearance. Ashing the extract reduced the toxicity as 

 indicated by appearance but not as indicated by the 

 weight of roots produced. The fact that the more di- 

 lute extract gave poorer results than the more concen- 

 trated in each case where a comparison is afforded 

 cannot be explained. 



While the evidence is not conclusive, consideration of 

 both the data and the photograph, indicates very 

 strongly that the cause of the toxicity of this extract is 

 inorganic rather than organic. On account of the re- 

 sults obtained with carbon black, the experiment was 

 repeated with slight variations. The ashing of the so- 

 lution, the separation into volatile and non-volatile 

 parts, and the treatment with carbon black were made 

 in the way already described. In this instance, the 

 precipitation was done by adding to the extract a small 

 amount of calcium oxide and shaking vigorously for 

 about twenty minutes, after which the solution was 

 left over night. It was tlien filtered and COo led in un- 

 til the extract gave no reaction with phenolphthalein. 

 The ])ortion treated with calcium chloride was given 

 enough c. p. CaCL. to make a N/20 solution. 

 The second leaching was obtained immediately after 

 the first. The data obtained and the treatments given 

 are found in Table IV. 



