CLASSIFICATION OF AMERICAN WHEAT VARIETIES. 29 



exserted. The edges of the sheath overlap on the side opposite the 

 blade. The sheaths may be either white or purple. During early- 

 growth they usually are quite scabrous, but become smoother at 

 maturity. There are some differences in these characters in the cul- 

 tivated varieties, but they are few and minute. After a careful study 

 the writers decided not to include any sheath characters in the de- 

 scriptions. 



The same decision was reached in regard to the minute differences 

 observed in the ligules and auricles. The ligules usually are short, 

 varying from 1 to 2 mm. long, and becoming lacerate as the plant 

 matures. Auricles always are present on wheat leaves. They are 

 narrow to midwide, usually strongly curved, with a few long strigose 

 hairs on the outer margin. The auricles often are purple in the 

 young stage, sometimes changing to white as the plant matures. 



SPIKE CHARACTERS. 



The entire inflorescence on one culm is called the spike. It is made 

 up of separate groups of flowers known as spikelets. These are 

 borne singly on alternate sides of a zigzag, flattened, channeled, 

 jointed rachis, parallel to its flat surface. At the base of each spike- 

 let, on the apex of each rachis joint, a tuft of short hairs usually 

 occurs. These hairs may be white or brown in color, but the differ- 

 ences are difficult to distinguish, partly because the hairs frequently 

 are discolored. 



Spikes differ greatly in form and degree of compactness. Club 

 wheats {Triticum sativum* compactum) have been separated from 

 common wheats (T. s. vulgare) principally because of their distinctly 

 compact or dense spikes. 



In distinguishing the cultivated varieties, four spike characters 

 are used. These are the awns, the shape, the density, and the erect- 

 ness of the spikes. 



AWNS. 



All varieties of wheat are classed here as awnless or awned. 

 Spikes of awnless and awned varieties, showing some of the varia- 

 tions that exist, are shown in Plate IV. The awns are important 

 agriculturally and usually are the character most readily apparent. 

 For these reasons this character has been given precedence over all 

 others in preparing the keys. Some early writers, as previously 

 stated, used this character for separating so-called species. 



Awnless varieties may have short or intermediate or no apical 

 awns, that is, awns near the apex of the spike. Whether the awns 

 are wanting or present, the varieties classed as awnless can be distin- 

 guished easily from varieties that are awned throughout. Apical 

 awns on varieties classed as awnless occur only on few to several of 

 the uppermost spikelets, except in a few varieties, and seldom, if ever, 



