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THE AMERICAN NATURALIST [Vol. XLYIII 



Conclusions 



The immediate (xenia) result of crossing varieties of 

 maize having sweet and waxy endosperm was the produc- 

 tion of seeds with a horny endosperm resembling that of 

 ordinary field varieties. In the second xenia generation 

 all the ears contained seeds of the three classes, sweet, 

 waxy and horny, in fairly definite ratios. The data were 

 arranged in accordance with the Mendelian formula corre- 

 sponding most nearly to the observed numbers. 



The third generation, like the second, gave results suffi- 

 ciently close to dihybrid ratios to render unprofitable the 

 assumption of more complicated ratios. There are, how- 

 ever, deviations from the expected numbers of too great 

 magnitude to be ascribed to chance. 



The ratios of waxy to non-waxy seeds were regular as 

 far as the conditions of the experiment could determine, 

 except for a slight excess in the number of waxy seeds in 

 nearly all the ears in which all three classes appeared 

 (Table IV). A deviation in number of waxy seeds as 

 large as that shown in the total would not be expected to 

 occur as the result of chance more often than once in one 

 thousand times. 



The ratios between sweet and horny, while approxi- 

 mating the predicted ratios, show numerous irregularities. 

 Wherever there is a significant deviation in the number 

 of sweet seeds, the observed number is below the expected. 

 Reasons are advanced for believing that the deficiency of 

 the sweet class may result from a failure of some sweet 

 seeds to develop a wrinkled exterior rather than from any 

 irregularities in segregation. 



The results show the value of representing the char- 

 acters by gametic factors. This method provides an 

 orderly arrangement of the facts of heredity thus far 

 observed with respect to these characters and makes pos- 

 sible fairly accurate predictions regarding the genetic be- 

 havior of the various seed classes. 



Washington, D. C, 

 July, 1914 



