76 
Journal of Agricultural Research 
Vol. XXVII, No. 2 
Actual differences in root systems of the three strains could not be 
expressed fully by the number of main roots; there were significant dif¬ 
ferences both in number and length of lateral roots (Plate 3). There 
was a very significant reduction in number of lateral roots in the strain 
susceptible to rootrot, both 2 to 8 inches below the surface and 10 to 16 
inches below the surface. The figures were 293.1 and 96 lateral roots 
compared with 391 and 244.6 roots, respectively. (Table VI.) Plants 
of the strain susceptible to leaf firing developed as many lateral roots 
near the surface as plants of the good strain, but there was a marked 
reduction in the number of lateral roots 10 to 16 inches below surface, 
or 160.2 lateral roots compared with 244.6 roots. Differences in total 
length of the lateral roots on the same number of main roots of an equal 
length were even more marked than differences in the number of lateral 
roots, and perhaps were more important from the standpoint of the physi¬ 
ology of the plants concerned. In the strain susceptible to rootrot there 
was less than half the total length of lateral roots 2 to 8 inches below 
surface and only one-fourth the total length 10 to 16 inches below the 
surface, or 334.4 inches and 103.5 inches compared with 774.7 inches and 
423.6 inches, respectively. (Table VI.) Roots of the strain susceptible to 
leaf firing were decidedly inferior to roots of the good strain in this 
respect, or 423.7 inches and 208.9 inches compared with 774.7 inches 
and 423.6 inches, respectively. All the differences in mean total length 
of all laterals on equal lengths of main roots from the different strains 
were significant from the standpoint of statistical analysis. 
Table VII .—Data from a comparative study of 10 plants of a good inbred strain of Yellow 
Dent corn and 10 and 5 plants , respectively, from two unrelated inbred strains susceptible 
to rootrot , planted May 22 , near Bloomington , III., in brown silt loam soil that pre¬ 
viously had produced three consecutive crops of corn , and excavated September 11-14 > I 9 22 
I 
j Mean total 
Mean total 
Mean total 
j number of 
length of all 
length of all 
Mean 
plant cir¬ 
cumfer¬ 
ence at 
base. 
Mean 
lateral roots 
lateral roots 
laterals per 
Character of strain. 
Num¬ 
ber of 
plants. 
Mean 
plant 
height. 
total 
number 
of main 
roots per 
per plant on 
six 6-inch 
pieces of 
main roots 
per plant on 
six 6-inch 
pieces of 
main roots 
plant on 
healthy roots 
only, in a 
horizontal 6- 
plant. 
6-12 inches 
6-12 inches 
inch section 
below sur¬ 
below sur¬ 
6-12 inches 
face. 
face. 
below surface. 
Inches. 
Inches. 
Inches. 
Inches. 
Good. 
10 
82. 8±i. 2 
3. 78±0.13 
41. 2±o. 4 
434 - 5 ± 33 - 5 
706.1 ±91.9 
4 * 343 - 9 ± 4 I 5 - i 
(a) Susceptible to root¬ 
rot. 
10 
102.3±i. 2 
3. 69±o. 11 
35-1±2. 0 
297. 6±i6. 1 
258. 8±2i. 8 
1, 220. 2 ±130. 7 
(6) Susceptible to root¬ 
rot. 
5 
90. 8±3. 7 
3. 7o±o. 12 
31. odbi. 1 
209. 8±23. 0 
208. 6±35.1 
946. 8± 153. 8 
Difference between 
good and (a) suscep¬ 
tible strain. 
19 - S±i- 7 
0. o9±o. 2 
6.1 ± 2. 0 
136. 9 ± 37 - 2 
447 - 3 ± 94 - 3 
3,123. 7±435- a 
Percentage difference 
between good strain 
and (a) susceptible 
strain.... 
2 3 * 5 
11. s 
14. 8 
3. 0 
3 i. 5 
3. 7 
63.3 
72. 2 
Difference/P. E;. 
i. 
4 - 7 
7. 2 
Difference between 
good and ( b ) suscep¬ 
tible strain. 
8. o±3. 9 
0. o8±o. 2 
IO. 2±I. 2 
224. 7^40. 6 
497 - 5 ± 98 . 4 
3, 397-1 ±482. 5 
Percentage difference 
between good strain 
and ( b ) susceptible 
strain. ! 
9. 7 
24. 8 
Si- T 
70. 4 
78. 2 
'HifFprpnf'p/P Tf'. 
2. 1 
1 
8.5 
5- 5, 
5. 1 
7 - 0 
! 
