1909] SCHREINER &• REED— OXIDIZING POWER OF ROOTS 367 



power of oxidation by the formation of brown- violet color, distributed 

 in the same manner as described for the roots which grew in the solu- 

 tions of naphthylamine. 



In order to learn whether the oxidizing powers of roots were 

 affected by conditions which favor growth, and also whether the 

 method used in the first experiment would show such differences, 

 the following experiment was made. Three water cultures were 

 made, in each of which an equal number of wheat seedlings of uni- 

 form age and size were employed. One culture was made with 

 redistilled water, the second with an aqueous extract of a rich garden 

 soil, the third with a dilute aqueous extract of well-decomposed 

 stable manure. After the plants had grown for one day in these liquids, 

 the oxidizing powers of the plants were observed by transferring 

 them to other bottles containing 2 parts per million of a-naphthyla- 

 mine in distilled water. At the expiration of 18 hours the intensity 

 of the purple colors showed that the roots which had previously 

 grown in the extract of garden soil had oxidized more naphthyla- 

 mine than those which had grown in distilled water, and those which 



had 



grown in manure extract had oxidized more naphthylamine than 



those from the garden soil extract. At the end of 24 hours the differ- 

 ences in color intensity in the two cultures were still more marked. 



The next experiment was an attempt to employ a method which 

 would permit a more accurate quantitative expression of the oxidizing 

 power of the roots. Two cultures of wheat seedlings were grown 

 for 5 days in an extract of unproductive soil, under the same condi- 

 tions as two other cultures in an extract of rich garden soil. Each 

 culture contained 6o cc of the respective soil extract. The oxidizing 

 Power of the roots in this experiment was shown by using phenol- 

 Phthalin. The phenolphthalin was prepared by the method given 

 m a previous paragraph, and 0.4" of the freshly prepared solution 

 were added to each culture of plants after they had grown 5 days in 

 th eir respective solutions. Nineteen hours after adding the indicator 

 aI1 Plants were removed from the cultures and the solutions rendered 

 Valine, thus producing the phenolphthalein color. The solutions 

 Were brought to the same volume by the addition of distilled water, 

 an d the relative amount of oxidation was measured by determining 

 tl] e color intensities of the different cultures. 



