CLASSIFICATION OF AMERICAN WHEAT VARIETIES. 23 
The keys and descriptions which are used here to distinguish and 
identify varieties are based on characters which show considerable 
variation and therefore are of value. 
MORPHOLOGICAL CHARACTERS. 
The following pages present in detail such morphological char- 
acters of the wheat plant as have been found in the present study 
to be of the most taxonomic value. The characters used to distin- 
guish the different species, subspecies, and lesser groups in the 
genus Triticum are often of no higher rank than the characters used 
to distinguish the cultivated varieties. 
In the preparation of the key certain primary characters have 
been used in a regular sequence. These characters are designated as 
major characters, and in the key they are printed in capitals. 
Certain other characters are used in the key to separate further: the 
closely related varieties. For this purpose any character is used 
which serves to distinguish the varieties under discussion. The 
same characters may not be used in two successive cases and they 
are not used in any definite order. These secondary characters are 
printed in ordinary type and are designated as minor charac- 
ters. The general principle followed in the choice of characters in 
the key was to progress from those most easily observed and most 
often occurring to those least easily observed or least often occur- 
ring. The principle governing the sequence of characters in the 
key is to progress from the absence of the character, as awnlessness, 
to the presence of the character and from the smaller size to the 
greater. 
The descriptions of the wheat varieties are arranged in a logical 
order of plant development. The major and minor characters used 
in the key are included in their proper places in the descriptions, 
as are many minor characters not used in the keys. 
All of the taxonomic characters which are used in the keys and 
descriptions of cultivated varieties are considered below in the order 
of their appearance in the descriptions. 
PLANT CHARACTERS. 
Certain plant factors which are genetically different in the several 
varieties are of value for classification purposes. These are the 
habit of growth, the period of growth, and the height of the plant. 
HABIT OF GKOWTH. 
All wheat varieties are here classified as having winter habit or 
spring habit of growth. These characters are shown in Plate II. 
In the keys to the cultivated varieties they occupy the seventh 
and last major position. Yarro (in Columella, 7^) writing before 
