VARIABILITY IN LINKAGE OF CHARACTERS OP MAIZE 
15 
to be greater in the male gametes when the crossing over was low 
in the males. Conversely, the variability should be greater in the 
female gametes when crossing over is low in the female. The data 
have been analyzed from this standpoint. The seven progenies 
having le-ss crossing over in the male than in the female gametes 
have a mean difference in o- 50 (<7 50 ? — a 5Q $ ), with the female gametes 
more variable, of 0.839 ±0.286; and the four progenies in which the 
crossing over in the female gametes was less than that of the male 
have a mean difference in cr 50 , also with the female gametes more 
variable, of 0.312±0.334. The difference of 0.525+0.439 between 
the two groups is not significant. Contrary to the hypothesis, the 
crossover rate in the female gametes is more variable when the 
percentage of crossing over is higher in the female than in the male 
gametes, but the difference between the mean of this group of 7 
progenies and that of the whole population of 13 is but 0.211+ 
0.356. There would thus seem to be no support for the idea that 
high variability is associated with a low rate of crossing over. 
VARIABILITY OF CROSSING OVER NO GREATER IN UPPER THAN IN LOWER EARS 
Although differences in the rate of crossing over between upper 
and lower ears are found in certain progenies, there are no con- 
sistent differences in the variability of the crossover rate in upper 
and lower ears. The standard deviation of the crossover ratio in 
upper and lower ears is practically the same, and this holds whether 
the heterozygous sex is male or female. The data for upper and 
lower ear groupings for three progenies are shown in Table 8. 
As in the comparison of variability in the two sexes, the absence 
of any correlation between the degree of variability and the apparent 
rate of crossing over indicates that a differential death rate of 
gametes or zygotes is not an important factor. 
Table 8. 
-Comparison of variability (c 5 o) in percentage of crossing over in 
upper and loioer ears 
Upper ears 
Lower ears 
Progeny 
Per- 
centage 
of cross- 
overs 
<r 
0"8O 
Per- 
centage 
of cross- 
overs 
<T 
CM 
Difference 
(c«o upper— 
0"6O lower) 
Male gametes: 
Dh 416L3L1C5L3L1R23 
Ph 230L1 and L2R24. 
Dh 416L3L1C5L4L1L24 
Female gametes: 
Ph 230L1 and L2R24 
18.3 
24.8 
37.4 
18.8 
36.0 
3.92 
4.68 
2.73 
5.38 
2.64 
5. 07±0. 85 
5. 41± . 82 
2. 82± . 43 
6. 88± . 58 
2. 75± . 32 
20.2 
28.1 
37.5 
19.7 
34.8 
2.83 
5.89 
2.13 
5.77 
3.19 
3. 52±0. 59 
6. 55± . 99 
2. 20± . 33 
7. 26± . 49 
3. 34± . 39 
1. 55±1. 04 
-1. 41±1. 28 
. 62± . 54 
— . 38± . 76 
Dh 416L3L1C5L4L1L24 
- . 59± . 50 
VARIABILITY OF CROSSING OVER NO GREATER IN THE BASE THAN IN THE TIP 
OF THE EAR 
In two progenies the lower and upper halves of the ear were 
classified separately. In one progeny this procedure was followed 
for both male heterozygous and female heterozygous plants, but 
in the other only the female heterozygous plants were so treated. 
