276 BOTANICAL GAZETTE [APRIL 
oxidation of aloin, is less in the young seedling and increases 
with age. 
The relative oxidation was determined by placing the seedlings 
in culture bottles, 10 seedlings to a bottle, with the roots in the aloin 
solution made by dissolving 400 milligrams in one liter of pure 
distilled water. In 20 hours the depth of color produced by the 
red oxidation product was measured in the colorimeter. Taking the 
reading for the 12-day seedling as 100, the relative oxidation of the 
8-day seedling was 81; of the 5-day seedling 48. 
Oxidation of aloin by roots is greater in darkness than in light, 
the relation being in three separate tests with 4, 6, and 9-day 
seedlings, roo in the darkness to 75, 70, and 71, respectively. 
Nitrates and phosphates increase the oxidizing power of the 
wheat roots, while potassium salts, especially potassium iodide, 
decrease it. “4 
TABLE I 
EFFECT OF SALTS ON OXIDATION OF ALOIN BY ROOTS : 
Relative oxidation 
Control in pure distilled water....... i 
won Mitte 50 p.p.m. NH; 135 
ROVE SUIGNAtG... 2: 50 p.p.m. K,O + 
Acid calcium phosphate............. 50 p.p.m. P.O; BME 
mOGIUA Hilfaté, 5,6 
Potassium eniphate —- =. 50 p.p.m. NH;, K,0, P,Os 10° 
Acid calcium phosphate x 
A Othanium Chloride. 4 sop.p.m. KCl 3 
Potassium iodide... .. . ee sop.p.m. KI gis 
WE 50p.p.m. I ” 
In the experiment given in table I, the seedlings were started 
germinating January 4, and were put into the nutrient solutions 
January 10. On January 14 the aloin was placed in the solution, 
and on January 15 the oxidation readings were made. 
The accelerating effect on oxidation of a solium nitrate solu- 
tion containing the equivalent of so p-p.m. of NH; and the retard- 
ing effect of potassium salts equivalent to 50 p-p-m. K.0 is shown 
likewise in the case of plants grown in darkness. In this case the 
plants 6 days old were put into the salt solutions containing 0.04 
per cent of aloin, and the experiment continued for 24 hours, we 
