8 o6 
Journal of Agricultural Research 
Vol. XXIII, No. io 
These two plants illustrate some of the differences commonly noted 
between plants which are resistant to the development of rots in the 
roots and stalks and those which become severely rotted. When the 
plants are vigorous and apparently healthy the quantities of the metals 
in the nodal tissues are nearly equal throughout the stalk and are not 
in sufficient quantity or in the state of combination with the plant 
tissues which causes the brownish purple discolorations. 
Furthermore, the accumulation of the metals in the basal nodal 
tissues of stalks showing symptoms of disease does not necessarily mean 
a larger quantity of metals in the stalk as a whole. It indicates pri¬ 
marily an unequal distribution of the metals, which can be observed 
readily by using the microchemical tests, compared with the uniform 
distribution which is characteristic of normal plants. 
The nodal plate from which the ear shoot originates frequently has 
the largest accumulation of all the nodes in the stalk. When this con¬ 
dition develops early in the life of the stalk the ears may form imper¬ 
fectly. The nodal tissues may become disorganized and consequently 
weakened (PI. io, B), so that the shanks may break over before the 
ears are completely matured, as is shown in Plates 6 and 16, B. When 
this happens the shank scars will show the typical pinkish to brownish 
purple discolorations, the color varying in intensity according to the 
time when the discolorations begin to develop in relation to the degree 
of maturity of the ear. 
This condition of the stalk is believed to be a very important factor 
affecting the rate of maturation of the ears. When the nodal tissues 
are affected, as shown in Plate io, B, the ears are delayed in their 
maturity and tend to remain starchy. It has been found that the dis¬ 
tribution of phosphorus also is affected in stalks with these accumula¬ 
tions of the metals. The phosphorus content of the nodal tissues is 
higher when the iron and aluminum compounds become concentrated 
in these tissues. The disorganization of the nodal plate tissues inter¬ 
feres with the movement of sufficient quantities of phosphorus and 
probably other materials to the developing ears and in this way may cause 
the ears on affected plants to remain starchy. The results of the inves¬ 
tigations upon this interpretation of one of the causes of starchiness in 
corn will be published in a subsequent paper. It is already a well-known 
fact, however, that adequate phosphates hasten the maturity of the ears. 
The mobility of the iron and aluminum compounds seems to be asso¬ 
ciated with a high sap acidity, according to preliminary tests upon 
normal and diseased stalks. The sap is distinctly more acid in the 
normal stalks than in those in which the nodal accumulations of the 
metallic compounds have taken place. Whether or not the decreased 
acidity is the result of a greater metal content of the stalks has not 
been learned. 
EFFECTS OF SOIL TREATMENTS UPON THE DESTRUCTIVENESS OF 
THE ROOTROTS 
In Plates 4, 12, A, and 13 the variations in the effects of the available 
metal salts are seen. The tall, vigorous plants in Plate 12, A, are the 
more resistant to the rootrots, while the smaller, stunted plants are sus¬ 
ceptible and the roots are actually being rotted. It is presumed that 
these stunted plants have grown from infected seed, yet when infected 
kernels from the same ears are planted in different types of soil the 
percentage of damage due to the rootrot is greater in those soils which 
have the larger amounts of available aluminum. 
