80 R. A. EmMERSonN 
tribution calculated on the basis of the three-factor hypothesis, the fit 
was very poor, P equaling 0.0002 (page 76). Comparison of the observed 
distribution with the distribution calculated on the four-factor basis follows: 
Dilute Dilute 
Color types Purple Sun red aingalls Snail Brown Green Total 
Ta ley apelin es Vv ‘Ig, Ivg, VI 
Observed: 6.4: ssees oe 309 100 67 19 88 98 681 . 
Calculated? :. 22.2... 287 96 72 24 96 106 681 
Difference............ +22 +4 —5 a —8 —8s 0 
Relation of aleurone color to plant color.— It is evident from the compari- 
sons already given that the four-factor hypothesis fits well the F2 data, 
which is of course to be expected since it was invented for that purpose. 
But this fact alone is far from a substantiation of the hypothesis. The 
genetic tests ordinarily available are the behavior of the several F2 types 
in later generations and in intercrosses. Since aleurone color as well as 
plant color is involved in these crosses, still another test can be employed. 
The six F; plants whose F. progenies are recorded in table 35 produced 
from self-pollination a total of 955 seeds, of which 388 had colored and 567 
coloriess aleurone. This obviously approaches closely a 27:37 ratio, the 
percentage of colorless seeds being 59.4 + 1.1 while the theoretical per- 
centage is 57.8 (Emerson, 1918). The deviation from expectation, 
1.6 + 1.1 per cent, is such as might be expected by chance once in three 
trials, P equaling 0.33. Evidently, therefore, the aleurone factors A, C, 
and F are concerned in these crosses. Since A and R are assumed by the 
hypothesis to be plant-color factors also, there is afforded opportunity of 
comparing the plant-color classes from colored with these from color- 
less seeds. Since colored aleurone requires the interaction of A, C, and R, 
colored seeds should never produce brown plants nor green plants of type 
VI, both of which are aa. As seen from the data given below, no brown 
plants came from colored seeds but a few wholly green plants appeared. 
Greens of type IVg are of course to be expected from seeds homozygous 
for R’. Owing to the fact that a larger percentage of colorless than of 
colored seeds produced plants, the theoretical distribution with respect 
to plant color, given below, was calculated separately for colored and for 
colorless seeds. For the colored seeds there are nearly two chances in 
