394 EK. P. DEatrRick 
is there oxidized to a higher oxide, as the insoluble brown deposit. Soon 
after the heavy deposition of the oxide, disintegration of the root occurs. 
Schreiner and Reed (1909) conclude that “the process of oxidation by 
roots is largely, if not entirely, due to the activity of a peroxidase produced 
by the roots.” That the deposit is not caused merely by the instability 
of the manganese solutions in the presence of organic matter is indicated 
by the absence of any blackening on pieces of string or wood placed in 
them. A definite relation has been established between stimulants of 
this oxidizing power and stimulants of growth. Schreiner, Sullivan, and 
Reid (1910:9) state that ‘“ oxidation by plant roots is a factor which 
has considerable agricultural interest, especially from the viewpoint that 
such oxidation is able to change the organic matter in the medium in 
which the plant is growing and that processes promoting oxidation play 
a large part in the best methods of soil cultivation.” 
The effect of manganese on the oxidizing power of the roots of wheat 
seedlings was therefore investigated. Seedlings were set up as before in 
nutrient solutions (931 parts per million of salts) and grown for two weeks. 
Portions of these solutions were then treated with small quantities of the 
aloin solution and allowed to stand for twenty-four hours, and a com- 
parison was then made of their relative oxidation. The results appear in 
table 14: 
TABLE 14. Errect or MANGANESE SULFATE ON OXIDATION By Roots 
Oxidation in solutions 
Parts per million of manganese === aS | 
With Without 
plants plants 
(UR EADS CeO Neale str LAOP WeRe WCE LOS eee. Teale a ae any Ss 100 0 
1 eit cee eee aaNet nas erate Me Dena Orne AX Peay bir Rainer oR 23 (3 184 0) 
By ah Rae BABU EN, ERR a UR RE Sele IESOOD  Re as etn eae a Na 191 0 
a Soe PiEg Tet RULES eee Re ee RET Po Spe oN i NE OA 181 0) 
LS URE ap arse eA teeta ere WR MR eG gO ESD RISA Or 244 9 
10) Uae abe er nite na maaan | Ria Ian pin ae tere a te 250 0 
OOO cre ERA ree BNL ER ete ERNE Pe Sak Sing pk ellos Mee ne oe 206 167 
In every case the cultures in which plants had grown oxidized the aloin 
more than did those in which no plants were grown. In fact, the aloin 
was but faintly oxidized in the checks, and with the exception of the one 
containing the greatest quantity of manganese the degree of oxidation 
