VARIABILITY EN LINKAGE OF CHARACTER* OF MAIZE 
19 
Aitenburg (i), working with Primula sinensis, measured the 
gametic proportions separately for individual anthers of a single 
plant. The number of offspring resulting from pollinations with 
single anthers was small, and in consequence only very large differ- 
ences in crossover rate could have been detected. Using his data for 
the crossing over between L and S 7 for the plant 4.2a. percentages 
ranging from 39.9±3.67 to 54.2 ±2.92 are disclosed. This range is 
found between two anthers from the same flower and is of magni- 
tude comparable with the large differences found between plants of 
maize. It can not be considered significant, however, in view of the 
errors and the fact that it is the largest difference of a possible 21. 
The data are shown in Table 13. 
The variability of crossing over in the six anther samples is as 
great as that found between individual plants in many maize prog- 
enies but the excess beyond the expected standard deviation (a) is 
not significant. 
Table 13. — Gametic proportions in individual anthers of a single plant of 
Primula sinensis 
[From Altenburg CO Table 2; 4.2a is plant number; 1 and 2 represent flower numbers; 2-1 to 5 represent anther 
numbers; samples in entries 2-6 are of anthers from a single flower] 
Entry No. and anther 
Gametic proportions 
L S 
Ls 
IS 
Is 
Total 
Percentage of- 
Crossovers 
(1) 4 2a 1-2- 
(2) 4 2a 2-1- 
(3) 4 2a 2-2- 
(4) 4 2a 2-3. 
(5) 4. 2a 2-4. 
(6) 4. 2a 2-5- 
Mean - - . 
q~5 o 
■y/pqIH. 
23 
37 
44 
28 
52 
37 
22 
12 
21 
12 
16 
14 
139 
132 
190 
78 
81 
65 
35.2 
40.9 
46.9 
449 
42 
47.7 
52 5 
53.1 
547 
57.7 
53.1 
50.8 
42. 6±2 83 
54. 2±2 92 
46. 5±2 44 
42 5±3. 78 
39. 9±3. 67 
46. 1±4 17 
45. 92±1. 45 
5. 35±1. 04 
5.02 
VARIABILITY OF CROSSING OVER NO GREATER IN OLD THAN IN FRESH POLLEN 
Age-of-pollen experiments, in which samples of pollen were col- 
lected early in the morning and each sample divided into two equal 
lots, one lot being used immediately and the other being held for 
about seven hours, furnish data suitable for determining the rela- 
tive variability of the crossover ratio in fresh and old pollen. 
Successful paired pollinations were obtained from 13 plants. From 
these plants the fresh pollen had a o- 50 of 3.39 ±0.45 and the old 
pollen a <r 50 of 3.72 ±0.50. The difference, 0.33 ±0.67. though in 
the direction of the crossover ratio, being more variable in old pollen, 
is not statistically significant. 
CROSSING OVER NO MORE VARIABLE IN FIRST THAN IN LAST GAMETES FORMED 
From the available evidence on the relative variability of the 
crossover ratio in young and old plants, it is not possible to detect 
small* differences in variability, since only seven plants functioned 
as early and late parents. The difference observed is in the direc- 
7 L is a factor for style length and £ is a factor for stigma cplor. 
