CLASSIFICATION OF AMERICAN WHEAT VARIETIES. 



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 f%j fl^ 



air spaces. \^y \l>r 



WIDTH OF THE CREASE. 







b 



FIg. 14. — Crease widths : a, 

 Narrow ; b, midwide ; c, 

 wide. (Natural size and 

 enlarged 3 diameters.) 



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 view. 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. 



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 

 (Natural size and anc [ ' 1S 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. Nearly all of the 

 durum and club wheats have a shallow crease. A few varieties of 

 common wheat have been described as having a " pitted V 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 



b 





do 



Fig. 15. — Crease depths : a, Shallow ; b, mid- 

 deep ; g, deep; d, pitted, 

 enlarged 3 diameters.) 



