594 
Journal of Agricultural Research voi. xxm, No. 8 
Table IX.— Relation of early vigor to rate of growth and yield of Funk y s Ninety-Day 
corn as influenced by pathologic condition of plants from which seed was selected , grown 
on clean soil at Bloomington , 77 /., in jgig 
Seed from ears ripening normally. 
Seed from ears ripening prematurely. 
Points considered. 
Vigorous. 
Semi¬ 
vigorous. 
Weak. 
Vigorous. 
Semi¬ 
vigorous. 
Weak. 
Total number of plants.. 
Percentage of plants in 
78 
138 
27 
61 
156 
27 
each group. 
Average height (in centi¬ 
meters) 15 days after 
32 .1 
56.8 
11. 1 
25.0 
63.9 
II. I 
planting. 
Average height (in centi¬ 
meters) 36 days after 
45.7 
38.5 
27.4 
44. 4 
36.8 
28.8 
planting. 
Average increase in 
height per plant (in 
centimeters) 21 days 
169.0 
154.2 
126. 6 
170. I 
I 50.3 
130.4 
after first record. 
Average yield per plant 
123.3 
IX 5 - 7 
99.2 
125.7 
114. 5 
101. 6 
(in grams). 
220. 5 
215.4 
177.8 
220. 2 
194. 8 
147.1 
Tables VIII and IX are of special interest because of the fact that the 
classification of plants as vigorous, semivigorous, and weak was made 
only 15 days after the com was planted and because the com was planted 
at the end of the normal com planting season in soil that had not grown 
com for 12 years. These results lend further emphasis to the strong 
correlation of early vigor and yield. 
In the experiments reported in Tables VIII and IX, the heights of the 
plants were taken 15 days after planting at the time of judging vigor, 
and again at 36 days after planting. In both measurements there is a 
fairly wide variance in the average heights of vigorous, semivigorous, and 
weak plants. In the period of 21 days between the first and second 
measurements all groups of plants made considerable gains in heights. 
A comparison of the average gains in plant height during this period shows 
that, in every comparison, the vigorous plants made the greatest gains, 
followed by the semivigorous plants, and then by the weak. It is evident 
that the more vigorous individuals not only retain their initial superiority 
in height but grow more rapidly than the less vigorous plants. The 
difference between the vigorous and weak plants in this respect is very 
marked. 
STUDIES OP PLANT POPULATIONS 
From the foregoing data and discussion it seems evident (1) that 
early vigor and yield of grain are closely correlated (PI. 4), also (2) that 
the percentages of strong, vigorous plants in populations grown from 
diseased seed are lower than in similar populations grown from relatively 
disease-free seed (PI. 6 and 7). Inasmuch as the total yield of a plot 
or field of maize depends on the total number of plants and the average 
yield per plant, it follows that the total yields of contiguous plots, 
differing from o to 8 per cent in field stand, will be more or less directly 
proportional to the percentages of strong, vigorous plants in the popula¬ 
tions. A large number of experiments have been conducted during a 
