INDEPENDENT MENDELIAN INHERITANCE 



79 



of these observations, particularly with respect to that pair of characters 

 concerned with cotyledon color. Johannsen has summarized these 

 results and examined them with reference to their agreement with the 

 conditions imposed by the laws of chance. Table VIII which has been 

 adapted from Johannsen shows that in a sum total of 179,399 counts 

 by seven different investigators the ratio was 3.0035:0.9965. The 

 probable error for this number of observations is 0.0028 so that the 

 deviation from the ideal ratio is slightly greater than the probable error, 

 but only so great that such a deviation would be expected approximately 

 twice in five times. 



Another case which has been investigated with very large numbers 

 is that of the contrasted characters starchy and sweet endosperm in 



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FIG. 37. Results of crossing starchy and sweet corn : a, Sweet parent ; c, starchy parent ; 

 b, the Fi showing complete dominance of starchiness; d, the Ft showing monohybrid 

 segregation ; e, f, g, and h, Fs populations, the last three obtained by planting Fi starchy 

 grains, the sweet ear, e, by planting an Fz sweet grain. (After East and Hayes.) 



maize. Those varieties of maize which have starchy endosperms have 

 smooth opaque grains whereas the varieties with sweet endosperms have 

 translucent, wrinkled grains. The difference is due to the fact that in 

 ripening there is a progressive formation of starch in starchy races, but 

 in sweet races the starch grains formed are small and angular and there 

 is an actual breaking down of endosperm materials into various kinds 

 of sugars. Correns has shown that starchiness is completely dominant 

 and segregation is sharp and unquestionable aside from very exceptional 

 cases of intergrading. Fig. 37 illustrates very well how sharply segre- 

 gation occurs in hybrid ears. The results of East and Hayes' extensive 

 investigations of segregation for this pair of characters are summarized 

 in Table IX. In this table families have been entered separately so that 



