THEORY AND PRACTICE 



olus with robust stalk that bears small flowers, 

 and another variety with small stalk that bears 

 large flowers. By crossing the two, and then in- 

 breeding the cross-bred progeny, you may expect 

 that in the second generation you will secure some 

 plants that will bear large flowers on robust stalks, 

 combining the good traits of the grandparents. 



But, as your experiments are extended, you will 

 presently be confronted with instances in which 

 the case is not so simple. You will be concerned 

 not merely with the size of stalk and size of flower 

 of your gladiolus, but with questions of color, of 

 abundant bearing, and of keeping qualities as well. 

 And you should know that with the inclusion of 

 each new character the application of the Men- 

 delian formula becomes increasingly complicated. 

 The fundamental principle, as just outlined, is not 

 altered, to be sure. Each pair of qualities (tall 

 stalk versus short stalk, large flower versus small 

 flower, red flower versus white flower, etc.) will 

 be carried forward quite independently of all the 

 other characters, and recessive traits will tend to 

 reappear in one individual in four of the second- 

 generation progeny. But, according to the simple 

 law of chances, it comes about that where two 

 pairs of Mendelian factors are in question the 

 recessive factors, although appearing in one in- 

 dividual in four of the progeny, will be combined 

 in the same individual in only one case in sixteen. 



And when three pairs of hereditary factors are 

 in question for example, tall or short vines, pink 

 or white flowers, and yellow or green pods, in 



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