PLANT COLORS IN Maze 31 
There are rather large differences between observed and expected 
numbers. The purples are considerably, and the sun reds slightly, in 
excess of expectation, while each of the other four classes has too few 
individuals. The probability that these deviations may be due to chance 
‘is approximately 0.11. One might expect, therefore, to encounter chance 
deviations of the magnitude observed here about once in nine such trials. 
This, of course, does not substantiate the three-factor hypothesis, but 
merely indicates that it is not necessarily out of keeping with the observed 
facts. 
Backcrosses with green VIc—— A better criterion perhaps is afforded by 
the backcross of F; purples with the green parent type. Records of such 
crosses are shown in table 3. The backcrosses with F,’s of table 1 are 
listed in group 1, and backcrosses with similar F; purples of other lots 
in group 2. The same six phenotypes observed in the regular F, generation 
occurred here also. On the basis of the three-factor hypothesis and with 
the assumption that there are three sorts of greens indistinguishable from 
one another, the individuals of this backcross should be distributed equally 
to five classes with the sixth class containing three times as many indi- 
viduals as any other class. The observed distribution of the 1317 indi- 
viduals of the fourteen progenies is here compared with the expected 
distribution: 
Sun Dilute Dilute 
Color types mUrple 54 uel aon re" Brown Green Total 
Observed........ 170 160 176 160 172 AO amy led 
Calculated....... 165 165 165 165 165 AGS 1320 
Ditterence: 2... . +5 —5 +11 —5 +7 —Il16- —3 
While a few of the backcross progenies listed in table 3 exhibit con- 
siderable deviations from the expected distribution, the fourteen lots 
taken together approximate it closely. The probability that the observed 
deviations may be due to chance in random sampling is about 0.85. 
Deviations as great as these are to be expected thru chance alone, there- 
fore, in about six out of seven trials. 
Working hypothesis— To the three factor pairs used to interpret the 
results here reported, the symbols A a, B b, and Pl pl have been assigned. 
The gene A is an anthocyanin factor. In the presence of aa ordinarily 
no anthocyanic pigment develops, tho brownish, or flayonol (Sando and 
Bartlett, 1921), pigment may be formed. The pair J 6 is nanicd for its 
2 
