VARIABILITY IN LINKAGE OF CHARACTERS OP MAIZE 
43 
Experiments prior to those of Emerson and Hutchison have little 
bearing on the question, since they were made before the wide fluc- 
tuation in the crossing over of individuals was appreciated, and the 
comparisons were not confined to plant reciprocals. 
The pairs of characters studied by Emerson and Hutchison were 
the b and Ig factors, for plant color and liguleless leaves, and the c 
and sh factors, for aleurone color and shrunken endosperm. 
The data presented on the b and Ig factors involved 19 reciprocal 
back crosses and showed no significant difference in the mean crossing 
over. The behavior of the individual ears is very uniform. The 
extreme departure from equality in the two sexes is four times the 
probable error,, and in a sample of 20 ears the odds against a de- 
parture of this magnitude are only 6 to 1. 
Crossing over between c and sh was measured in two seasons. In 
1920, 29 reciprocal back crosses of Emerson and Hutchison (6, Table 
3) gave a mean crossover difference of 1.12 ±0.186, the lower rate be- 
ing in the male. The difference is more than six times the probable 
error. The mean difference i s taken from the totals and the probable 
error is calculated from cr—\/pq/n, wherein ^=the total number of 
seeds. The mean of the array of differences weighted with the 
reciprocals of their probable errors is 1.30 ±0.27. Calculated in this 
way the D/E is slightly lower, but the difference is undoubtedly 
significant. 
Taken by themselves the results of Emerson and Hutchison indi- 
cate a significantly lower crossover difference for the character c-sh 
when both recessives enter in the same parent, but since differences 
of the same order are found between closely related progenies in our 
material there is little reason for associating the difference with 
coupling and repulsion series. 
Table 25. — Summary comparing the percentages of crossing over in male and 
female gametes of plant reciprocals 
Num- 
ber of 
recip- 
rocals 
Female gametes 
Male gametes 
Difference * 
Entry No. and progeny designa- 
tion 
Num- 
ber of 
seeds 
Per- 
cent- 
age of 
cross- 
overs 
Num- 
ber of 
seeds 
Per- 
cent- 
age of 
cross- 
overs 
?-<? 
Stand- 
ard 
devia- 
tions 
D/E 
(1) Dh 416L3L1C1L1L22 
(2) Dh416L3LlClLlLlL23— -i- 
(3) Dh416L3LlClLlL2L23 
(4) Dh416L3LlClLlL3L23 
(5) Dh416L3LlC3L21. 
4 
7 
8 
7 
5 
5 
5 
7 
17 
49 
11 
13 
13 
1,.919 
3,400 
3,064 
2,933 
2,331 
3,296 
4,068 
3,523 
7,336 
24, 627 
5,284 
4,995 
4,122 
24.75 
25.80 
31.41 
31.00 
27.16 
28.25 
32.57 
39.40 
35.50 
20.47 
22.16 
20.62 
25.10 
1,885 
2,104 
2,686 
1,387 
4,100 
2,266 
7,352 
3,661 
6,300 
27, 517 
3, 683 
4,693 
3,757 
20.53 
24.50 
32.36 
30.50 
23.20 
22.11 
29.65 
35.80 
37.60 
18.07 
27.42 
16.71 
29.30 
3. 34±0. 50 
3. 42=1=1. 66 
-1. 41±1. 00 
2. 66±1. 52 
2. 19±2. 25 
6. 78±2. 16 
4. 97± . 91 
3. 76± . 99 
-2. 85± . 77 
2. 78± . 49 
-5. 60± . 70 
4. 93± . 75 
-3. 48±1. 02 
1.47 
6.52 
4.19 
5.97 
7.44 
7.18 
3.01 
3.87 
4.73 
5.07 
3.43 
4.00 
5.47 
6.68 
2.06 
1.41 
1.75 
.97 
(6) Dh416L3LlC3LlL22___ 
(7) Dh416L3LlC5L21 
3.14 
5.46 
(8) Dh416L3LlC5L4L23 
(9) Dh416L3LlC5L4LlL24 
(10) Dh 416L3L1C5L3L1R23 
(11) Dh 416L3L1C5L3L2R23 
(12) Dh417LlL2LlL21._. 
3.80 
3.71 
5.67 
8.00 
6.57 
(13) Dh 417L1L2L1L2L23 
3.41 
Total 
151 
70, 898 
71, 391 
i The minus sign indicates those cases where there was more crossing over in the male than in the female 
gametes. 
