CHARACTERS IN AN UPLAND-EGYPTIAN COTTON HYBRID. 9 
Bract, number of teeth was determined on the longest bract of the involucre. Pima 
(in 1917 and 1918) gave a higher mean for this character than Holdon. 
Bract dentation index is the length of the terminal tooth of the longest bract, 
expressed as a percentage of the bract length. A high dentation index indicates 
that the bract is deeply toothed or rather cleft. Holdon exceeds Pima in the mean 
index of bract dentation. 
Bract tooth spread, graded. The size of the grade number indicates the degree of 
divergence of the teeth of the bract, grade 1 indicating an erect position. Pima 
gave a higher mean grade for this character than Holdon. 
Calyx dentation, graded, indicates the degree of indentation of the calyx, ranging 
from a slightly undulate but entire margin (grade 1) to a deeply toothed condition 
(grade 6). Holdon gave a higher mean grade for calyx dentation than Pima. 
Calyx gland abundance, graded. The size of the grade number indicates the 
relative abundance of oil glands per unit of surface. The number of the oil glands 
rather than their conspicuousness and regularity of distribution was the criterion in 
grading. The mean grade for calyx gland abundance was higher in Pima than in 
Holdon. 
Corolla length, measured in millimeters. Pima gave a higher mean than Holdon 
for this character. 
Corolla index, width of the corolla at the summit 10 as a percentage of the length. 
A high index indicates that the corolla is relatively broad and flaring when fully 
expanded. Holdon gave a higher mean for corolla index than Pima. 
Petal color, graded, the palest color (Holdon) being indicated by grade 1 and the 
deepest yellow (Pima) by grade 5. 
Petal spot, graded, the lowest grade number (0) indicating complete absence of 
the spot, as in the Holdon parent, and the highest grade number indicating the 
greatest intensity of the spot in the Pima parent. The variation in F 2 appeared to 
be in the density rather than in the kind of pigment present. The red pigment of 
the spot was never mixed with the yellow ground color of the petal. There was also 
great variation in the size of the red area, but in grading the endeavor was to consider 
the intensity rather than the size of the spot. Individual flowers on many of the F 2 
plants differed greatly in respect to this character, the range in some plants having 
amounted to four grades. In such cases that flower open at the time of grading which 
showed the highest degree of red pigmentation in this area was selected, although, 
if the time available had permitted, it would have been preferable to determine the 
average grade of numerous flowers on each plant. 
Stamen length, measured in millimeters on five stamens from a single flower on 
each plant, the average of the five measurements being taken as the value for the 
plant in question. Holdon gave a higher mean for stamen length than Pima. 
Anther color, or, more precisely, color of the pollen, was determined by grading, 
grade 1, that of the Holdon parent, representing the palest and grade 6, that of the 
Pima parent, the deepest yellow color. 
Pistil length, in millimeters, measured from the base of the staminal column to 
the summit of the stigmas. Pima gave a higher mean than Holdon for this character. 
Stigma index is the length of the stigmas or free (extracolumnar) portion of the 
pistil, measured in millimeters and expressed as a percentage of the total length of 
the pistil. A hi^h stigma index indicates that the stigmas are relatively long. The 
Pima mean was higher than that of Holdon. 
Boll lock number. The numbers of bolls of different lock numbers on each plant 
were determined, and from these data the mean lock number for all bolls on the 
plant was computed. All bolls were included which were large enough early in 
October to permit the determination of the number of locks without sectioning. 
Holdon gave the higher parental mean. 
Boll length, measured in millimeters. Pima gave the higher parental moan. 
Boll diameter, in millimeters, measured at the height on the boll where the diam- 
eter is greatest. Holdon gave the higher parental mean. 
Boll index. Boll diameter expressed as a percentage of the length of the boll. 11 
A high boll index indicates a relatively broad boll. Holdon gave the higher parental 
mean. 
Boll apex index is the diameter of the boll 5 millimeters below the apex expressed 
as a percentage of the maximum boll diameter. A high boll apex index indicates 
that the boll is relatively broad near the apex. Holdon gave the higher parental 
mean. 
10 The endeavor was to measure the width as soon as possible after the expansion of the corolla had 
been completed. In 1he case of the Fi grown in 1920 the measurements wore made probably too early in 
the morning, and the constants for corolla index in this population are therefore omitted in Table 1- 
The parental populations of 1919 did not differ significantly in mean corolla width. 
11 The same expression of boll shape was used by Balls' (4, p. 60). 
42433—23 2 
