14 BULLETIN 1074, U. S. DEPARTMENT OF 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 
seeregate, 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 1s 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 
