U2, R. A. EMERSON 
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four color types was closely approached in the results, x2 equaling 0.80. 
The comparison of observed with expected results follows: 
Bente types Weak Weak Dilute Dilute 
purple sun red purple sun red Total 
Ib IIb Illa 1Va 
Observediwsn wrasse, 21 28 22 27 98 
Calculated. i wes 24.5 24.5 24AN5 24.5 98 
Ditterences icy ee 3.55 3-5)" —==2.5 2h 0 
The progeny of a purple plant heterozygous for BB”, Pl pl, and the 
endosperm color pair Y y, backcrossed with a white-seeded weak sun red 
plant, A BY ply, affords evidence of another kind with respect to the 
interrelations of strong and weak purple and of strong and weak sun red. 
It has been noted previously (page 60) that Pl pl and Yy are linked, with 
a somewhat irregular percentage of crossing-over. The backcross gave 
the four color types purple, weak purple, sun red, and weak sun red, in 
the numerical relation 60:48:59:62. The observed deviations from the 
equality expected of a dihybrid are such as might occur by chance more 
than once in two trials, P equaling 0.54. The distribution of these 229 
plants to the four color types when the progeny of yellow seeds and that 
of white seeds are considered separately is as follows: 
Color types Purple lace Sun red Were Total 
asc lil Ila IIb 
Miellowascedspyiy eee 48 36 8 ire 109 
Wiknibevseeds <Caehat a Marc 12 12 51 45 120 
Evidently weak purple, assumed to be A B” Pl, here bears the same 
relation to weak sun red, A B” pl, that purple, A B Pl, is known to bear 
to sun red, A B pl. In case of the purples and the sun reds alone, the 
linkage of Pl pl with Y y is shown by 99 non-crossovers to 20 crossovers, 
or 16.8 + 2.7 per cent of crossing-over. When the weak purples and 
the weak sun reds are alone considered, the non-crossovers are to the 
crossovers as 81:29, a crossover percentage of 26.4 + 2.8. While the 
