22 
BULLETIN 1468 ? IT. S. DEPARTMENT OF AGRICULTURE 
linkage in the two sexes. The other two represent the reciprocal 
combinations that produce all four combinations without linkage. 
Table 15. — Comparison of the variability of the percentage of crossing over 
with that of the Mendeliah characters 
Entry number 
and progeny 
Back-crossed ears 
(1) C c wx wx on 
c c Wx WX- . 
(2) C c Wx wx on 
C C WXWX-. 
(3) Homozygous 
for C, het- 
erozygous 
for E.. 
Selfed ears: 
(4) 
Back-crossed ears, 
Lanham, 1924 
* (Dh 416L3L1- 
C5L4L1L24): 
(5) Colored 
horny 9X 
white 
waxy cf— - 
(6) White waxy 
9X color- 
ed horny 
& 
(7) White horny 
9X color- 
ed waxy cf- 
(8) Colored 
waxy 9X 
white 
horny 9-~ 
Page 
cita- 
tion, 
Kenn> 
ton 
(11) 
85,87 
85,87 
Num- 
ber 
of 
ears 
30 
2 19 
2 23 
Num- 
ber 
of 
seeds 
9,961 
9,065 
10, Oil 
20,483 
15, 760 
10, 716 
6,657 
8,124 
White 
Per cent 
50. 3±0. 37 
50. 3d= . 39 
48. 7± . 51 
26. 3± . 20 
48. 6=fc . 28 
48. 3± . 33 
48. 2± . 40 
49. 5± . 46 
Standard 
devia- 
tions (o). 
2. 51±0. 26 
2. 40± . 26 
3. 84± . 40 
1. 84± . 14 
Waxy 
Per cent 
49. 4±0. 36 
49. 7± . 44 
50. 2± . 47 
24. 2± • 25 
3.03=b .2249. 9± .33 
2.68± .23 
2. 46± . 27 
3. 25± . 32 
46. 3± , 
50. 0=b . 39 
Standard 
devia- 
tions Co") 
2. 45±0. 26 
2. 70± . 30 
3. 56± . 37 
1 2. 30± . 18 
3. 53± . 23 
1. 08+ . 27 
Crossovers 
Per cent 
50. 5±0. 27 
26. 6db . 78 
51. 5± . 47 
50. 1± . 62 
. 0=b . 40 
37. 3± . 38 
2. 41± . 26:50. 7±1. 10 
45. 3d= . 30 2. 14± . 21 49. 4± . 
Standard 
devia- 
tions (a-) 
1. 81±0. 19 
!4.85± .53 
3. 58± . 37 
3. 81± . 30 
14.40± .29 
i3.15± .27 
3. 14± . 34 
2. 58± . 26 
1 Standard deviations (a-) corrected to 50 per cent. 
2 9 c c Wx wx, c? Cc wx wx. 
39 Cc wx wx, <? c c Wx wx. 
There are two instances in Table 15 where the relation of linkage 
to the variability of the crossover classes may be tested by comparing 
the standard deviation of two closely related progenies in one of 
which there is no linkage. 
In lines 1 and 2 the standard deviation of the percentage of 
crossover classes in 21 ears with no linkage is to be compared with the 
standard deviation of the percentage of crossing over in 19 ears of 
the same parentage showing linkage. The variability of the linked 
group is greater by 4.85 ±0.53 per cent, a difference that is more 
than five times the probable error. The standard deviation of the 
percentage of crossing over in the ears with linkage also exceeds 
the standard deviation of the percentage of waxy by 3.5 times the 
probable error. 
In lines 5 and 6 combined, where there was linkage, the standard 
deviation of the percentage of crossing over is 3.99±0.21. This is to be 
compared with the percentage of crossover classes in lines 7 and 8 
where there is no linkage, 2.85±0.21. The difference of 1.14±0.3 
is 3.8 times the probable error. It would appear that linkage 
increases the variability of the crossover classes. 
