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THE AMEBIC AN NATURALIST [Vol. LI 



The second generation plants showed all degrees of 

 awning, from the perfectly awnless condition to those 

 which were one hundred per cent, awned like the Burt 

 parent. These Fo individuals were first grouped accord- 

 ing to percentage of awned spikelets, with a class range 

 of ten per cent. (Table I.) 



31-40 

 41-50 

 51-60 

 61-70 



The occurrence of plants having varying percentages 

 of awned spikelets and forming a more or less continuous 

 series between the parental types, at first suggested a 

 multiple factor condition for awning. A study of the 

 frequencies, however, showed that such an assumption 

 was incorrect. The frequencies of the zero and 100 per 

 cent, classes were too high to accord with an hypothesis 

 of this sort. 



When the plants were grouped in the classes— awn- 

 less, partially awned, and fully awned, it was seen that 

 the data approached, in a general way, a ratio of 1:2:1. 

 (See Table II.) The ratio of the first two named classes 

 to the third was found to be 4.15 : 1, or, on a basis of four, 

 3.22:. 78. 



It remained for a study of the Fg material, however, to 

 throw light upon the number of factors concerned in this 

 cross, and the relation of these factors to each other. 



