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THE A3IEEICAN NATURALIST [Vol. LIII 



has been tested as to its inheritance as yet, but it is 

 planned to do so. 



Trabut^ says in regard to the possible origin of hull- 

 less oats that "the study of the domestication of Avena 

 presents, from the genetic point of view, some rather 

 substantial arguments in favor of an ambient medium, a 

 modifying agent causing fluctuations which end in the 

 formation of varieties well characterized and fixed by 

 selection." 



Previous Woek 

 A number of investigators have studied hybrids be- 

 tween varieties of Avena nuda and Avena sativa. Nor- 

 ton'' was the first investigator in America to hybridize 

 these forms. He reports that 



the spikelet of the naked varieties usually has more than three grains, 

 while in the hulled types three grains is the limit. The first generation 

 plants produced a head naked at the top and hulled at the bottom. In 

 the second generation, one fourth of the progeny were typical naked 

 plants, one fourth were hulled, and one half like the first generation 

 hybrids. The naked plants all had long spikelets with more than three 



grains. In future generations no exception to this rule has been found 

 except that one second generation plant of a cross between European 

 Hull-less and Garton's Tartar King which seems to have become fixed in 

 the intermediate hybrid type. In this example we have an extremely 

 rare case of the fixation of a heterozygote or hybrid type, 



G-aines^ reports having made some hybrids between 

 hulled and hull-less oats and first separated the types 

 into two groups, hulled and hull-less. In making such a 

 grouping the heterozygous types were put into the group 

 which it resembled most. He obtained from one cross 

 48.7 per cent, hulled and 51.3 per cent, hull-less plants 

 and says, ''this indicates an intermediate about half- 

 way between hulled and hull-less for the heterozygous 

 types. As was mentioned above, the separation was 

 made arbitrarily into hulled and hull-less, according to 

 the type any given plant most nearly resembled." 



3 Journal of Heredity, Vol. 5, p. 84, 1&14. Translation of original paper. 



4 American Breeders' Association, Vol. Ill, p. 285, 1M7. 

 8 Washington Agr. Expt. Sta. Bui. 135, p. 58, 1917. 



