Feb.i6, 1934 
Inheritance of Petal Spot in Pima Cotton 
503 
ence for all 11 progenies having amounted to 0.5 grade and the difference 
having been significant in 8 of the progenies. A similar comparison in 
10 dominant parental and F 3 progenies showed no consistent tendency 
to greater development of the petal spot in the retarded as compared 
with the earlier-flowering plants. 
Table XII. —Evidence of increase or diminution of the petal spot in nonsegregating 
F z progenies as compared with populations representing the respective dominant or 
recessive parent of the cross 
Population. 0 
DOMINANTS 
Parental 13-8. 
F 3 24-46. 
Parental 12-13 
F 3 20-14. 
Mean grade of 
petal spot. 
i 
Difference between means, 
showing petal spot in F3 as 
compared with parental pop* 
ulation to have been— 
Increased. 
Diminished. 
! 8. i±o. 028 
| 8. 4± .031 
i 8. i± . 032 
7 - 5 ± -055 
o. 6±o. 064 
RECESSIVES 
Parental 1-3-12-14-2. 
F 3 20-19. 
Parental 1-3-12-14-2. 
F 3 20-24. 
Parental 3-2-4-1-22. 
F 3 21-22. 
1 
2. i± 
1. o± 
2. I± 
1. I± 
2 . 0 ± 
• 9 ± 
• 059 
• 054 
• 059 
.051 
. 056 
. 040 
i 
} 
I. I zfc . 080 
i. o ± . 078 
I. I± . 069 
a The parental population in each case comprises two progenies taken as one array. 
As a measure of the comparative earliness of the several populations, 
the mean number of flowers per plant during the first four days of the 
grading period (July 14-17) was computed for each parental population 
and homozygous F 3 progeny. The correlation between the progeny 
means for number of early flowers and grade of petal spot was then 
computed separately for the 10 recessive and for the 10 dominant pa¬ 
rental and F 3 populations. There was found to be a pronounced nega¬ 
tive correlation in the case of the recessives, the coefficient having been 
—-67i.ro. In other words, recessive progenies in which many of the 
plants were late in development tended to have a relatively high mean 
for petal spot. The dominant populations, on the other hand, showed 
an entire absence of correlation between earliness and grade of petal 
spot. 
Both the dominant and the recessive parental populations, which were 
situated together at one end of the plat, proved to be inferior to most 
of the F 3 progenies in flower production at the beginning of the grading 
period. Many of the plants in the parental progenies did not begin to 
flower, or flowered very sparingly, until near the end of the grading 
period. Since, in the spotless populations, retardation of growth tends 
to a more pronounced expression of the spot, it is obvious that the means 
for petal spot grade of backward and of more advanced recessive popu- 
