586 
Journal of Agricultural Research vd. xxm, no . § 
EXPERIMENTAL METHODS 
The investigations here reported include data on approximately 153,000 
com plants grown (1) in experimental plots in the vicinity of Bloomington, 
Ill., in the four years 1918 to 1921, on uniform, well-drained, fertile soil, 
classified by the Illinois Soil Survey (18) as brown silt loam; (2) on the 
Agronomy South Farm of the Illinois Agricultural Experiment Station, 
University of Illinois, Urbana, a brown silt loam (19 ); and (3) on an 
experimental plot near Yates City, Ill., also a brown silt loam (20). The 
seed, representing varieties differing in length of growing season, was all 
selected before a killing frost, carefully dried, and properly stored. 
The term 44 relatively disease-free,” wherever used in the tables, refers 
to seed showing no symptoms of infections by any of the root and stalk 
rot pathogenes, including species of Gibberella, Fusarium, and Diplodia. 
This information was obtained by testing representative samples on the 
limestone-sawdust table germinator described by Holbert and Hoffer (17). 
The term 44 diseased” refers to seed showing such infections when tested 
by this same method. The testing of every kernel of a great number of 
seed ears has given abundant evidence that usually not all the kernels 
on ears classed as “relatively disease-free” are actually free from infec¬ 
tions. Nor is every kernel on ears classed as diseased actually infected; 
in fact, the percentage of infected kernels in any of the diseased seed lots 
used usually was less than 50. The term 44 nearly disease-free” refers 
to seed lots as nearly free from infection as it was possible to have them. 
The plots were hand planted in hills 42 inches apart each way at the 
rate of three kernels per hill. Great care was exercised throughout the 
season to avoid mechanical injury of the plants during cultivation and to 
guard against ravages of insect pests and rodents, but no attempt was 
made either to thin to a uniform stand or to correct for differences in 
stand. When there was any appreciable damage due to these causes 
the experiments were discarded entirely. Both acre yields and indi¬ 
vidual plant yields were recorded in terms of the weight of dry shelled 
com. Acre yields have been reduced to a uniform moisture basis. 
Measurements and other readings taken in connection with these 
investigations were not made on plants selected at random; every indi¬ 
vidual plant in each of the various experiments herein reported was 
measured and the measurements were included in the data. Plant 
height was measured to the tip of the tallest leaf. Stalk circumference 
was measured at the middle of the first intemode above the ground 
surface. 
Each plant was studied in the early growth stages from the standpoint 
of vigor and classified as either vigorous, semivigorous, or weak. This 
classification was based on the general appearance of the plant, including 
size, color of foliage, apparent freedom from disease symptoms, and other 
characters usually associated with vigor. With few exceptions these 
records were made about 30 days after planting. 
For three years com inoculation studies have been conducted in cooper¬ 
ation with Dr. James G. Dickson, of the Office of Cereal Investigations, 
United States Department of Agriculture, and the Wisconsin Agricultural 
Experiment Station, to investigate further the relation of Gibberella 
saubinetii, the common wheat-scab organism (23 ), to the root and stalk rots 
of com. It has been found that this organism, under conditions to be dis¬ 
cussed in other papers, may be very active in reducing early vigor of com 
plants. A limited number of these dataare included in this paperto show 
