Mar. IO, X9a$ 
Aluminum and Iron Compounds in Corn Plants 
809 
and to show that the soil has a marked influence upon the growth of the 
com plants and their relative susceptibility to the rootrots. 
From the foregoing observations of field conditions under which root- 
rots prevail, and from the study of the results obtained in experimental 
plots located in various parts of the Com Belt, the evidence seems to 
indicate that the soil environment determines in a large measure whether 
the plants become severely infected or remain relatively healthy. When 
kernels from the same seed ears were planted in plots in Iowa, Illinois, 
Indiana, and Ohio the amounts of rootrot which would develop in the 
different ear rows was influenced by the soil and growing season more 
than by the organisms present in or upon the seed planted. 
METHODS USED TO DETECT METALS IN STALKS 
During the summer of 1919 it was discovered that large quantities of 
iron compounds, in organic combinations, were constantly present in 
the nodal tissues which were colored purplish brown. The micro¬ 
chemical method used to detect the iron compounds in these tissues con¬ 
sisted in placing the tissues in a strongly acidulated (HC 1 ) 20 per cent 
solution of potassium thiocyanate. When the stalks were tested in the 
field a stellite knife was used to cut them and the solution was applied 
directly to the exposed stalk tissues. By this means many hundreds of 
experiments and observations were made upon plants in all stages of 
development, and it was learned that the brownish purple nodal dis¬ 
coloration was associated with a relatively large quantity of iron com¬ 
pounds which accumulate in these tissues. Invariably the plants which 
were stunted in their development (PI. 4, A, B), those whose leaves 
became streaked with yellow or reddish purple, those with excessive 
firing of the leaves, those with prematurely broken shanks (PI. 6, A, B; 
16, A, B), and those which fell over early in the field, as shown in 
Plate 13, A and B, are the plants which constantly are characterized by 
discolorations and frequent disorganizations of their nodal tissues. 
QUANTITY OF ACCUMULATIONS INFLUENCED BY SOIL TYPES 
The quantities of iron and aluminum which accumulate in plants grown 
from kernels from the same seed ear vary according to the nature of the soil 
in which the plants grow. An experiment was conducted in the station 
greenhouse in 1919 wherein soils representing types from different coun¬ 
ties in Indiana were used, as follows: Soil from the field shown in Plate 4, 
B, representative of a calcium-deficient soil in Shelby County; soil from 
Bartholomew County, later found to be lacking in phosphorus; and a 
soil from Sullivan County, which was deficient in calcium. All pots were 
kept under relatively uniform conditions of moisture, temperature, 
and light. A rich garden soil was used as a control. 
Table I shows the record of growth of three stalks in each of these four 
soils. The sign — indicates a trace of iron present in the nodal tissues 
when tested chemically, X indicates a large quantity, and o indicates 
no trace whatever. The series of signs represent the nodal content for 
each node in the stalk with the lowest node in the stalk representd at the 
left end of the series and the uppermost node in the stalk represented 
at the right end. 
The best plants grew in the garden soil. They were normal green in 
appearance and had the iron compounds uniformly distributed through¬ 
out the stalk. This occurs in stalks of g ood, vigorous growth. These 
27135—23 - 1 } ~~ " ......'.' 
