CLASSIFICATION OF AMERICAN WHEAT YAEIETIES. 
45 
chief taxonomic characters are the width and the depth. Shrunken 
kernels nearly always have a relatively wide and deep crease, while 
in extremely plump or yellow-berry kernels the crease is narrow 
and shallow because the space beneath the 
bran is occupied by large starch cells and 
air spaces. 
^VIDTH OF THE CREASE. 
The width of the crease is determined by 
the distance between the crests of the cheeks 
on each side of the crease. Creases are de- 
scribed as narrow, midwide, and wide. These 
differences are illustrated in the cross sections of kernels shown in 
Figure 14. A narrow crease is about two-thirds or less of the total 
width of the kernel in ventral vie\v. The midwide crease, which is 
typical of most varieties, is usually about four-fifths of the total 
kernel width. A wide crease is almost the total width of the kernel. 

C^ 
w 
a 
h 
c 
Fig. 14.- 
-Crease w 
■idtlis : 
a, 
Narrow ; 
h, midwide ; 
c. 
wide. 
(Natural 
size 
and 
enlarged 
3 diameters.) 
DEPTH OF THE CREASE. 
The depth of the crease in this classification has been determined 
by an external examination rather than by a cross section of the 
kernel. The depth, therefore, is measured from the crest of the 
cheeks to the position where the crease is closed. No measurements 
of the portion of the crease below the surface of the kernel have 
been considered. Crease depths are described as shallow, middeep, 
and deep. These differences are shown by cross sections of kernels 
in Figure 15. A shallow crease has a depth of 20 per cent or less of 
the dorsoventral thickness of the kernel. A middeep crease has a 
depth from 15 to 35 per cent of the thickness of the kernel, and a 
deep crease has a depth of 30 to 
50 per cent of the thickness of 
the kernel. 
The depth of the crease is of 
taxonomic value only when the 
kernels are normally developed 
and is a distinguishing char- 
acter in only a few varieties. It 
is sufficiently constant, however, to be of use in describing varieties 
grown under identical and normal conditions. Xearly all of the 
durum_ and club wheats have a shallow crease. A few varieties of 
common wheat have been described as having a " pitted " crease. This 
is characterized by having a distinct opening near the center of the 
crease (Fig. 15, d). The sides of the opening usually are wrinkled. 
The pitted character is most marked on the kernels of the Humpback 
and Huston varieties. 
a 
h 
cC 
Fig. 15. — Crease depths : a, Shallow ; b, mid- 
deep ; c, deep; d, pitted. (Natural size and 
enlarged 3 diameters.) 
