INBREEDING FOR PURE TYPES 
In putting this method into operation it is first necessary to 
purify into stable, pure strains some of the corn from the 
regular varieties. This is accomplished by control pollinat¬ 
ing so that the same plant is both female and male parent. 
As the small ear shows up on the selected plant a small 
bag is placed over it before any silks emerge. When the 
tassel of this plant ripens and sheds pollen some of the 
pollen is collected in a larger bag. The small bag is lifted 
off the ear, and, at the same instant the larger bag is slipped 
over the ear and the pollen dusted on the silks. The larger 
bag is slipped into place over the ear to protect it from 
foreign pollen. 
The process just described, fertilizing the silks of an ear 
with pollen from the tassel of the same plant, is known as 
self-fertilization or inbreeding. The next spring, when 
such inbred ears are planted in ear rows, a large number 
of weaknesses show up, such as dwarf plants, plants with 
rolled leaves, individuals with weak roots and weak stalks, 
leaves of pale color or lacking in green material, plants 
•\yhich are smutted or otherwise diseased and plants having 
various desirable and undesirable characteristics too nu¬ 
merous to list here. Year after year inbred seed ears are 
harvested from the better plants—planted in ear rows— 
again self-fertilized and the better plants selected. After 
five to eight years of such inbreeding and selection uniform 
appearing types are developed which are known as inbred 
strains or pure lines. 
Inbred strains are not suitable for the corn producer since 
they yield only one-half to one-third as much as the 
varieties from which they were started. Keep this in mind. 
CROSSING INBRED STRAINS 
When two of these inbred strains are crossed, however, the 
yield lost on inbreeding is usually regained. Not all such 
crosses are satisfactory. The only way known of evaluat¬ 
ing them is to grow such crosses in performance plots for 
comparison with each other and with standard varieties 
using yield, quality, lodging, etc., as a basis for judgment. 
Recombinations of two inbred strains are known as Single 
Crosses, and, while they would be suitable for commercial 
production, the practice is not generally used due to high 
production costs brought about by low yield of inbred 
mother parents and difficulty in producing sufficient inbred 
seed for large field plantings. 
For commercial hybrid seed two single crosses, with no 
common parent, are combined to produce what is known as 
double cross seed. Here again the crosses must be grown 
and compared in order to evaluate their fitness for actual 
farm use. We emphasize again that not all recombinations 
of inbred strains are high yielding and desirable in other 
respects. 
Detasselled Hybrid Seed Field: on The Funk Farms. The 
two detasselled rows are the Hybrid seed producers and are 
the only rows from which seed is harvested. No seed is 
saved from the single row (male parent) vjith tassels. 
Experimentally, crosses between inbred strains and single 
crosses are produced by the same method used in self- 
fertilization or inbreeding except that pollen is taken from 
a selected unrelated strain instead of being taken from the 
same plant. 
DETASSELLING CORN 
Quantity production of hybrid corn necessitates use of other 
means of control pollination. In order to increase supply 
of seed of inbred strains they are grown in isolation plots. 
These plots are located at distances of one-fourth mile or 
more from other corn. Since inbred strains are genetically 
pure, inter-pollination between the plants produces pure 
line seed instead of hybrid seed. 
Single crosses are produced in quantity by planting un¬ 
related inbred strains in alternate rows in isolation plots 
described above. Tassels of these unrelated strains are 
pulled out before any pollen is shed. This detasselling 
leaves only the one source of pollen, the tassel-bearing in- 
bred strain being the male or pollen parent of all the corn 
in the plot. Therefore, the detasselled rows furnish single 
cross seed while the rows with tassels furnish pure line 
seed. 
SUMMARY: YIELD OF FUNKS HYBRID CORN COMPARED TO OPEN POLLINATED VARIETIES ON 84 FARMS IN 1933 AND 124 FARMS IN 1934 
Kind of Corn 
YIELD CLASSES Bushels per Acre 
Average Yield 
Bu. per Acre 
Increase in 
yield in favor of 
Funks Hybrid 
15 to 
24 bu. 
25 to 
34 bu. 
35 to 
44 bu. 
45 to 
54 bu. 
55 to 
64 bu. 
65 to 
74 bu. 
75 to 
84 bu. 
85 to 
94 bu. 
95 to 
104 bu. 
105 to 
114 bu. 
SEASON OF | 
1933 
Funks Hybrid Corn. 
5 
14 
12 
8 
18 
17 
4 
5 
1 
63.7 
8.3 
Open Pollinated Varieties. 
3 
7 
17 
14 
18 
10 
7 
7 
1 
55.4 
SEASON OF 
1934 
Funks Hybrid Corn. 
6 
14 
18 
34 
26 
15 
6 
4 
1 
51.3 
12.5 
Open Pollinated Varieties. 
25 
24 
37 
14 
13 
9 
2 
38.8 
NOTE: Funks Hybrid Corn yielded only 12 bushels (Average) less in 1934 than in 1933 while the Open Pollinated Varieties yielded 16 bushels less in 1934. It 
has been our observation in the past that Funks Hybrid Corn gives a better account of itself in unfavorable seasons than do the Open Pollinated Varie¬ 
ties. We refer you to the Agronomy Department of the University of Illinois for results of the Illinois Performance Tests in 1934. 
