78 
Journal of Agricultural Research 
Vol. XXVII, No. 2 
HISTOLOGICAL STUDIES 5 
After it became known that there were marked differences in the 
extent and gross structure between the root systems of the good strain 
and the strain susceptible to rootrot, material was prepared to determine 
whether there was also any marked difference in their cellular structures. 
Cross sections were made from the roots of six plants of each strain. All 
the preparations from each strain showed very similar cellular structures; 
in fact sections from any two plants were as much alike as sections from 
two roots of the same plant. But where sections of the two strains were 
compared a decided difference was noted. (PI. 4 and 5.) The number 
of tracheids per root in the two strains was the same, but in the good strain 
they were large and oval in cross section, while in the strain susceptible 
to rootrot they were considerably smaller and round. The most im¬ 
portant difference, however, lay in the cell arrangements of the pith and 
cortex. The cells of the good strain were closely united so that the cells 
had an angular shape. The corners were usually reinforced by extra 
thickenings. In the strain susceptible to rootrot these cells were round 
and were not closely bound together, neither did they have any thicken¬ 
ings in the spaces between the cells. Measurements of the cell walls of 
the pith and cortex also showed that the thickness of the cell walls of this 
strain was slightly less than that of the good strain, regardless of the 
special reinforcements possessed by the cells of the latter. Thus these 
preliminary studies indicate that there is a considerable difference be¬ 
tween the roots of these two strains in the morphology of the cells them¬ 
selves, which may account for some of the desirable qualities of the good 
strain. 
CONCLUSION 
From the foregoing data it is evident that extent and distribution of 
root systems are very important factors in determining the economic 
importance of different strains of corn and their adaptability to various 
conditions. 
6 Acknowledgment is made to Prof. F. E. Wood and Dr. R. Hayes of the Illinois Wesleyan University 
for assistance and use of equipment in preparing the histological material. 
