1909] 



SCHREINER & REED-OXIDIZING POWER OF ROOTS 



371 



dismantled 



It seems, therefore, highly improbable that the oxidizing activities 

 of microorganisms can be responsible to any appreciable extent 

 for the results observed. 



OXIDATION IN SOIL EXTRACTS 



Following the preliminary experiments already described, further 

 experiments were made to study in more detail the oxidizing power 

 of plants grown in extracts of soil of different character. These exper- 

 iments were chiefly designed to study the oxidizing powers of plants 

 in extracts of good and poor soils, of extracts treated with absorbing 

 agents, and in distillates of soil extracts. 



The difference in oxidizing power of plants in extracts of fertile 

 and infertile soils is shown by the following experiments. Jn the 

 first experiment, an extract of Takoma lawn soil was compared with 

 an extract of good Leonardtown loam. The former is a very unpro- 

 ductive soil, and the latter is a much better and usually a very pro- 

 ductive soil. The oxidizing powers of the plants were determined 

 by adding phenolphthalin to the cultures, after the plants had gro*n 

 in them for nine days. The growth and oxidizing powers of the 

 Plants are shown in Table III, relative to control cultures made in 

 distilled water, which are represented as 100 in each case. 



TABLE III 



r 1 i in #»vtracts of Takoma lawn 

 Comparative growth and oxidizing powers of J^ n ^^ re ^ tra n3 P iration. 

 soil and good Leonardtown loam. Growth expressed in terms ot ma^ = J == 



Xo. 



Solutions 



I 



2 



3 



Controls in distilled water 

 Extract Takoma lawn soil 

 Extract Leonardtown loam 



Relative 

 growth 



Relative 

 oxidation 



IOO 

 33 



IOO 



7 2 

 286 



com 



"inter weather, December ,o to ly, the plant grow in « »» - 

 W the figures for transpiration did not have ttme -£££»£ 

 'dative productiveness of the two extracts, since ^ 



found that the Leonardtown loan, extract pjoduces m * 

 setter plants than distilled water. The figures do show, howc , 



