16 
BULLETIN 1164, U. S. DEPARTMENT OF AGRICULTURE. 
number of individual plants (180) which the population comprised. 
The numbers on the axis of abscissas are those of the several grades. 
For characters determined by grading the numbers indicate the origi- 
nal grades under which the population was classed, except that in the 
case of fiber length, as explained on a preceding page, the plant aver- 
ages of the original grades were reclassified in nine final grades. For 
./-?-? 
■£ a- r <3 £> 
s-o 
J-O 
tf 
V- 
\ 
so 
«*<? 
JO 
/=> 
JO 
<so 
Kt 
^o 
/o 
f/ 
/o 
o 
/?' 
o 
f^ 
/23 + S&7-0& 
P 
// 
/ 
N 
4 
sA 
\ 
V 
z 
\ 
Fig. 3.— Axis length: Frequency distribution of 
Holdon X Pima F 2 cotton piants, by grades, 
as used in computing the correlations. The 
ordinate figures indicate the number of plants 
as a percentage of the total population. 
Fig. 4.— Axis internode length: Frequency dis- 
tribution of Holdon X Pima F 2 cotton plants, 
by grades, as used in computing the correla- 
tions. The, ordinate figures indicate the num- 
ber of plants as a percentage of the total popu- 
lation. 
measured characters and indices based upon measurement the total 
range of the actual values was subdivided into a number of grades 
of equal range. This was done to facilitate calculation of the coeffi- 
cients of correlation on the tabulating machine, but it was found 
convenient to plot the frequency distributions on the same basis. 
In addition to the F 2 frequency distributions, the diagrams show 
by means of short vertical lines the positions on the curve of the 
so 
' 2 3 * S S 7 3 
s> 
1 
— 
■90 
JO 
20 
/O 
O 
1 
SL 1 
/ 
M 
\ 
/ 
f 
N 
\ 
t 
/ 
\ 
// 
Fig. 5.— Axis internode number: Frequency dis- 
tribution of Holdon X Pima F 2 cotton plants, 
by grades, as used in computing the correla- 
tions. The ordinate figures indicate the num- 
ber of plants as a percentage of the total pop- 
ulation. 
so 
so 
*o 
30 
20 
/0 
o 
/ -c 
? J 
f 
* 
r 
5" / 
" 3 & 
1 
. 4 
<> 
1/= 
// 
Fig. 6.— Fruiting branch length: Frequency 
distribution of Holdon X Pima F 2 cotton 
plants, bv grades, as used in computing the 
correlations. The ordinate figures indicate 
the number of plants as a percentage of the 
total population. 
means of the parental populations (H and P) grown in the same year 
and of the hybrid ¥ x grown in 1920. The ranges of the parental 
progenies are indicated by horizontal lines at the bottom of the figure. 
The wide variation occurring in the second generation of this hybrid, 
in regard to most of the characters determined by measurement or 
grading, is clearly shown by the frequency distribution curves. The 
