74. R. A. EMrerson 
namely, a B pl (VIa), ab Pl (VIb), ab pl (VIc). Still another type of 
green — a type wholly devoid of purple, red, or brown pigment — has been 
used in several crosses, with results quite unlike those obtained from corre- 
sponding crosses with the other green types. For reasons that become 
apparent later, this fourth type of green is regarded as genetically similar 
to dilute sun red and is known as type IV¢g. 
Green IVg x brown V 
Generations F; and F,— When brown, aB Pl, is crossed with green 
of any of the three types previously studied, brown appears in F, and 
brown and green in F2. If green Vic, ab pl, is used in the cross, the F, 
ratio approaches 9:7, while if green Vla, a P pl, or Vib, ab Pl, is used, 
3:1 F, ratios are of course expected (tables 19 and 20, page 135). In 
striking contrast with such results are those obtained from a cross of 
brown with green IVg. Two such crosses gave 78 purple plants in F,, 
and a third cross resulted in 72 purple and 63 sun red plants. It will be 
recalled that just such results as these were obtained from crosses of dilute 
sun red with brown (tables 4 and 14, pages 123 and 131). The brown plant, 
2031-20, which gave purple and sun red F, plants: when crossed with green 
IVg, was the identical plant previously reported (table 4, group 2) to have 
given 55 purples and 55 sun reds when crossed with a dilute sun red plant. 
Moreover, this same brown plant was shown (table 20, group 2, page 135) 
to have produced from self-pollination 82 browns and 34 greens. Evi- 
dently it was aa BB PI pl. The important point here is that crosses 
of brown with green [Vg give exactly the same results in Fy as if green 
IVg were a dilute sun red, A A 6b pl pl. 
There are other reasons, in addition to the F; results of crosses with 
brown, for supposing that green IVg has the factor A. When the pericarp- 
color gene P occurs together with A, the resulting pericarp color is always 
red, but when P and aa are associated the pericarp color is brown. When 
green IVg plants have pericarp color it is red rather than brown, while 
that of greens Via, VIb, and VIc is always brown. Again, the A factor 
is known to be essential to the production of aleurone color (Emerson, 
1918), and the stock of [Vg green plants used in these crosses, a strain 
of the variety Black Mexican sweet corn, was homozygous for purple 
aleurone. It is noteworthy in this connection that many, perhaps most, 
plants of this variety show very slight traces of sun red, and these traces are 
