VAEIABILITY IN LINKAGE OF CHAKACTEBS OP MAIZE 
17 
effect that the homozygous recessive parent might have on the 
gametic proportions. In entries 6 to 9 of the table the data are as- 
sembled without respect to whether the two pollen samples were ap- 
plied on the same day or to the same double recessive parent. 
Table 10. — Comparison of the variability of crossing over in a population with 
that of samples from single individuals 
[Comparison is made between the standard deviation (cr) of the differences between paired samples and 
that of the sums of the samples and also between the upper and the lower halves of the ears] 
Progeny 
Sex of 
gametes 
Num- 
ber of 
ears 
Num- 
ber of 
pairs 
cr difference 
cr sum 
Difference 
(cr sum— cr 
difference) 
DIE 
Paired samples: 
(1) Dh416L3LlC5L3LlR23. 
8 
10 
10 
32 
17 
13 
16 
8 
8 
2. 30±0. 39 
5. 47± . 83 
1.72± .26 
5. 59± . 47 
4. 77± . 55 
3. 53± . 47 
2. 58± . 31 
3. 61± . 61 
3. 65± . 62 
4. 75± . 35 
6. 56± . 61 
1. 90± . 29 
7. Mil. 20 
8. 38±1. 26 
4. 46± . 68 
9. 52± . 80 
3.40± .40 
5. 92± . 78 
9. 72±1. 16 
11. 00±1. 86 
4. 46± . 76 
10. 84± . 78 
11. 58±1. 08 
14. 10±2. 12 
4. 84±1. 26 
2. 91±1. 51 
2. 74± . 73 
3. 93± . 93 
-1.37± .68 
2. 39± . 90 
7. 14±1. 20 
7. 39±1. 96 
. 81± . 98 
6. 09± . 85 
5. 02±1. 24 
12. 20±2. 14 
3.8 
(2) Ph 230L1 and L2R24 
(3) Dh 416L3L1C5L4L1L24.. 
(4) Ph 230L1 and L2R24 
...do 
-.do 
Female.. 

1.9 
3.8 
4.2 
(5) Dh416L3LlC5L4LlL24_- 
(6) Dh 416L3L1C5L4L1L24 . 
...do 
Male . 
2.0 
2.7 
(7) Dh416L3LlC5L3LlR23-- 
(8) Dh416L3LlClLlL2L23_- 
(9) Dh416L3LlC5L4L23 
Ear base and tip samples: 
(10) Dh416L3LlC5L3LlR23. 
(11) Dh 416L3L1C5L3L2R23 . 
(12) Dh 416L3L1C5L3L2R23 . 
...do 
...do - 
—do 
Female 
...do 
Male 
43 
26 
10 
6.0 
3.8 
0.8 
7.2 
4.1 
5.7 
Table 10 shows that in general the samples of gametes from the 
same individual are less variable than the population as a whole. It 
is equally obvious, however, that in some progenies the samples are 
not less variable. In these cases it will be noted that the standard 
deviations are relatively low, and as a matter of fact in these prog- 
enies no correlation in the rate of crossing over is found between 
the paired samples, indicating that the progenies have reached 
genetic uniformity with respect to crossing over. 
As a further check on the relative variability of the percentage of 
crossing over in several samples of a single individual compared 
with that of single samples of several individuals, two plants are 
available in a single progeny from one of which five samples of 
pollen were taken and from the other four samples were taken. 
These samples are all of the male gametes, and the standard devia- 
tions may be compared with that of the population of male gametes 
as a whole for this progeny. The plant from which five samples of 
pollen were taken had a standard deviation (o- 50 ) of 2.78 ±0.59 and 
that furnishing four samples had a standard deviation of 4.50 
±1.07 (corrected for size of population). These standard deviations 
(Table 11) are to be compared with that of 2.82 ±0.22 for the popu- 
lation as a whole. In this progeny, therefore, it would seem that the 
individual plants did not vary among themselves in the rate of 
crossing over to an extent greater than did the several samples of 
single individuals. This conclusion is further supported by the 
results cited in entry 9 in Table 10 where two samples of pollen 
were used from each of eight plants in this same progeny. 
Additional comparisons between the variability of individuals and 
that of the samples from a single individual are afforded by three 
lots of ears in which the upper and lower halves were classified 
19987°— 27 3 
