64 R. A. EmMerson 
the dilute sun reds. For sun reds and dilute sun reds, the non-crossovers 
are to the crossovers as 229:115, or a crossover percentage of 33.4 + 1.7. 
For purples and dilute purples, the relation is 254:121, or a crossover 
percentage of 32.3 + 1.5. It follows from this that the factor pair, B b, 
which differentiates sun red, A B pl, from dilute sun red, A 6 pl, is the 
same as that which differentiates purple from dilute purple. And this 
is in keeping with the hypothesis under test, in accordance with which 
purple and dilute purple have been assigned the genotypes A B Pl and 
A b Pl, respectively. 
In a single progeny resulting from a backcross of a heterozygous normal- 
leaved purple plant with a liguleless-leaved green plant, greens occurred, 
as expected, with about three times the frequency of the average of 
the other five color classes. The progeny included 14 browns and 49 
greens. Of the normal-leaved plants there were 10 browns and 19 greens, 
and of the liguleless-leaved plants 4 browns and 30 greens. On the basis 
of the hypothetical genotypes assigned to browns and greens, and with 
the assumption of 33 per cent of crossing-over between Bb and Lg lg, 
the four classes, normal brown, normal green, liguleless brown, and 
liguleless green, should bear the relation 2:4:1:5. For a total of 638 
plants, the relation would be approximately 11:21:5:26, whereas the 
observed relation was 10:19:4:30. The deviations from expectation are 
such as might occur by chance in more than three out of four trials, P 
equaling 0.78. In this case, as in the others reported, the linkage relations 
between Bb and Lg lg afford support for the view that the several color 
types bear the relation to one another inferred from the hypothetical 
genotypes assigned them. 
Summary of results involving A a, Bb, Pl pl 
The results of the cross of purple with green — which gave in F» six 
color types, namely, purple, sun red, dilute purple, dilute sun red, brown, 
and green, with a numerical relation of approximately 27:9:9:3:9:7 
from selfed Fy’s and about 1:1:1:1:1:3 from F;,’s backcrossed to green — 
have been interpreted on the basis of the interaction of three factor pairs, 
Aa, Bb, and Pipl. This hypothesis has been subjected to practically 
every genetic test available, as summarized below. 
Each of the six F, color types has in turn been tested by its behavior 
in F'3, and in several cases behavior in Fy and even in later generations 
