VAHIABILITY IN LINKAGE OF CHABAOTEHS OP MAIZE 
47 
provided conditions more favorable to the development of the cross- 
over classes than upper ears, this condition is not found to be general 
for all progenies. 
A closely related progeny grown at Lanham, Md., in 1924, gave 
the results shown in Table 29. Ten pairs of ears are listed, which 
provide a test of the influence of ear position on the proportion of 
crossover to noncrossover classes in the male gametes. Of these 10 
pairs 7 have a higher apparent rate of crossing over in the upper than 
in the lower ears, and the mean weighted difference in favor of a 
higher rate for the upper ears is 1.55 ±0.37 per cent. This dif- 
ference is more than four times the probable error and is doubtless 
significant. 
From this same progeny there are 17 pairs of ears borne on the 
heterozygous female plants. These ears provide the opportunity to 
measure not a selective action on the male gametes but differences 
in the rate of crossing over in the formation of the gametes of the 
two inflorescences, or possibly survival rates after the gametes are 
formed. Of the 17 pairs, 10 show a higher rate of crossing over for 
the upper ears, but the mean weighted difference of 2.15 ± 0.78 per 
cent can not be considered significant. The data are also given in 
Table 29. 
Table 29. — Crossing over in upper and lower ears where male and female 
gametes are measured 
[Progeny Dh 416L3L1C5L4L1-1-L24 for male gametes; progeny Dh 416L3L1C5L4L1-4-L24 for female 
gametes] 
Upper ears 
Lower ears 
Difference 
Plant designation 
Number 
of seeds 
Percentage 
of crossovers 
Number 
of seeds 
Percentage 
of crossovers 
(lower- 
upper) 
Male gametes measured: 
3581X3998 
824 
518 
295 
355 
364 
596 
325 
408 
491 
635 
33. 3il. 11 
38. 5il. 44 
39. 9il. 92 
43. 7il. 77 
37. 8i 1.71 
39. 5il. 35 
37. 7i 1.28 
34. 9il. 59 
36. 8i 1.47 
37. 2il. 29 
148 
181 
69 
371 
628 
592 
86 
77 
344 
139 
34. 0i2. 63 
36. 5i2. 42 
39. 2i3. 97 
40. 6i 1.72 
35. 6i 1.29 
37. 7i 1.34 
35. 6i2. 34 
33. 0i3. 62 
39. 8i 1.78 
38. 8i2. 78 
0. 7i2. 86 
3601X3997 _._. 
-2. 0i2. 82 
3604X3989 
— . 7±4. 42 
3618X4010 
-3. Ii2.47 
3620X3998 
-2. 2i2. 14 
3631X3998 
-1.8il. 91 
3442X3986. _ 
-2. Ii2. 67 
3655X4019 
-1.9i3.96 
3664X4022 
3. 0i2. 31 
3666X4022 ; 
1. 6i3. 06 
Mean 
-1. 55i3.37 
Female gametes measured: 
3984 _ 
560 
698 
813 
495 
166 
245 
355 
434 
349 
242 
188 
118 
555 
397 
136 
410 
502 
35. 5il. 36 
37. 2il. 23 
38. lil. 15 
33. 3i 1.42 
35. 5i2. 50 
38. 8i2. 10 
34 8il. 70 
35. 5il. 55 
33. Oil. 70 
39. 2i2. 12 
33. 6i2. 32 
40. 9i3. 06 
40. 7i 1.40 
32. 7il. 59 
35. 8i2. 77 
31. 2il. 54 
36. lil. 44 
154 
448 
444 
61 
86 
276 
444 
27 
423 
554 
15 
249 
454 
355 
410 
119 
306 
36. 4i2. 61 
31. 5il. 47 
36. 4il. 54 
25. 5i3. 76 
35. 7i3. 48 
36. 4i 1.95 
37. 6il. 55 
29. 7i5.92 
39. Oil. 60 
37. 9i 1.39 
22. 3i7.24 
34. 2i2. 03 
31. Oil. 46 
36. 3il. 72 
33. lil. 56 
34. 5i2. 94 
29. 5i2. 95 
. 9 i2. 94 
3985 
-5.7 ±1.92 
3986 . 
-1.7 ±1.92 
3988 
-7. 8 ±4. 02 
3992 
. 2 ±4. 28 
3993 
-2. 4 ±2. 87 
3994 
2. 8 ±2. 30 
3996 . 
-5. 8 ±6. 12 
3998 _. 
6. ±2. 34 
3999. 
-1. 3 ±2. 53 
4000. 
-11.3 ±7.60 
4004 
-6. 7 ±3. 67 
4008... -. 
-9. 7 ±2. 02 
4009 
3. 6 ±2. 34 
4010 .. . — 
-2. 7 ±3. 18 
4020.* 
3. 3 ±3. 33 
4022 
-6. 6 ±2. 27 
-2. 15± . 78 
