14 BULLETIN" 1074, TJ. S. DEPARTMENT OE AGRICULTURE. 



After growing, for a couple of years, several pure-line strains of 

 the same variety obtained from several sources, one of the strains 

 was selected as the standard for the variety. The descriptions here 

 recorded, therefore, should represent the true type of the variety. 

 In certain cases, however, material was limited to samples obtained 

 from only one or two sources, and in these cases the judgment of the 

 writers in selecting the pure strain which correctly represents the 

 variety may not be as accurate as where more samples of the same 

 variety were available. 



. Many varieties here described are badly mixed in commercial fields 

 wherever they are grown. Mention of this sometimes is made in the 

 descriptions. In many cases this will account for differences observed 

 between a variety and its description, as here recorded. In other 

 cases all the characters which are here recorded may not become ap- 

 parent in some localities, and this may cause some confusion. The 

 failure of stem and glume colors to develop in some sections is an 

 example of this. 



Natural crossing between wheat plants occurs quite commonly in 

 the western United States. In the classification nurseries several 

 hybrid rows have been found each year. These had been sown from 

 material which was apparently pure the previous season and which 

 was grown from a single head. In some instances the hybrids were 

 not noticed until the second generation when they were segregating. 

 This natural crossing has caused some difficulty in describing vari- 

 eties, especially because hybridization between closely related vari- 

 eties could not always be detected. 



Several hundred mixtures obtained from experimental plats and 

 commercial fields were grown in the classification nurseries for iden- 

 tification. A few proved to be mechanical mixtures of varieties 

 grown in the locality, but most of these were new types. These 

 probably originated, for the most part, from natural hybrids, with 

 possibly an occasional mutation. Many of the types continued to 

 segregate, thus proving their hybrid origin. Those which came true 

 to type were either mutations or the homozygous progeny of hybrids. 

 As the progeny of a cross nearly all tend to become homozygous after 

 being grown several years, it is believed that practically all of the 

 new types can be accounted for in this way. Many of the new types 

 closely resembled American or foreign varieties, but were not identi- 

 cal in all characters. 



Practically every field of wheat contains some plants which can 

 not be identified with any known variety. These are easily found, 

 because of their differences from the remainder of the plants in the 

 field. Many of these forms, in all probability natural hybrids or 

 mutations, have been submitted to the writers for identification, but 

 as a rule this is not possible. Considering the opportunities for the 



