CLASSIFICATION OF AMERICAN WHEAT VARIETIES. 



33 



The covering and coloring of the glumes are major characters of 

 the second and third place, respectively. The length and width of 

 the glumes also are used, but are of only minor importance. 



COVERING OF THE GLUMES. 



Fig. 2. — Glume covering : a, 

 Glabrous : b, pubescent. 

 (Natural size and en- 

 larged 3 diameters. ) 



Glumes of all varieties here discussed are described as glabrous or 

 pubescent (Fig. 2). Host (119) placed the pubescent-glumed wheats 

 in a separate species called Triticum villosum. Several later authors 

 also considered pubescent wheats as different species. This character 

 is used here, however, only as a major one in separating varieties, but 

 is given the second place in the keys because 

 of the definite and striking contrast between 

 absence and presence. This action is in ac- 

 cordance with the usage of Koernicke and 

 Werner. 



Glumes described as glabrous are without 

 any covering of hairs. Those described as 

 pubescent are more or less covered with hairs 

 of varying length. Pubescence usually is 

 readily apparent. The degree of pubescence 

 varies in the different varieties. On some the 

 hairs are much longer and more numerous than 

 on others. Glumes of some durum varieties 

 are partly glabrous and partly pubescent, but 

 are classed as pubescent. In such varieties the pubescence is most 

 often found on the edge of the glumes. 



COLOR OF THE GLUMES. 



Differences in glume color were early recognized. Lamarck (134) 

 used these distinctions in classifying varieties. Glume color is here 

 used as a major character and occupies third position in the key be- 

 cause of the distinct differences which are readily apparent when 

 the plants are mature. This is also in accordance with the usage of 

 Koernicke and Werner (133). All glumes are classed as white, 

 yellowish, brown, or black. These colors are shown in Plate III, 

 Figure 2. 



Glumes classed as white may vary in color from a cream or pale- 

 straw color to a dark yellow (PI. Ill, Fig. 2, a and b). Practically 

 no glumes arc without color. Within the class, however, there are 

 two rather distinct shades. Some taxonomists have classified them 

 separately as white and yellowish. In the present bulletin, however, 

 both shades are placed in t\\<'. same class and described only by the 

 one term " white," except in the case of the durums, which are classed 

 separately as white and yellowish. In the, descriptions the glumes 

 of some varieties of common wheal are described as being yellowish 

 95589°— 22— Bull. 1074 3 



