CLASSIFICATION OF AMEKICAN WHEAT VARIETIES. 



35 



longer than the lemmas and is separated from the other species prin- 

 cipally on this distinction. The length of the glume is here de- 

 scribed as short, midlong, or long. Heuze (112) and Scofield (173) 

 used essentially these same terms. Most varieties of wheat have 

 midlong glumes. A few varieties, however, are distinct in having 

 either short or long glumes. Short glumes may have lengths vary- 

 ing from: 6 to 10 mm. Midlong glumes may vary from 8.5 to 12.5 

 mm., and long glumes from 11 to 15 mm. The glumes of Polish 

 wheat exceed this latter measurement and are described as very long. 



WIDTH OF THE GLUMES. 



The width of glumes is used in the same manner as the length. All 

 glumes are described as being narrow, midwide, or wide (Fig. 4). 

 These differences were pointed out by Scofield (173). The width of 

 the glume is here determined across its center from the keel to the 

 margin of the outer side. Narrow glumes may vary in width from 2 

 to 4 mm., midwide ones from 3 to 5 mm., 

 and wide ones from 4 to 6 mm. The 

 differences are small, and much over- 

 lapping of the classes is inescapable. 

 Wide glumes nearly cover the lemma 

 at the point of measurement, while nar- 

 row glumes usually cover less than a 

 third of i£. 



b 



fait nl i mi 

 Fig. 4. — Glume widths: a, Narrow; 

 6, midwide ; e, wide. (Natural 

 size and enlarged 3 diameters.) 



TENACITY OF THE GLUMES. 



Glumes of different varieties vary in 

 tenacity or the firmness of attachment 

 to the rachis. The glumes of most 

 varieties, especially of the durums and 

 clubs, are persistent. Some varieties of common wheat, however, 

 have glumes which are easily deciduous, causing the spikes to shatter. 

 This character is mentioned only for such varieties. 



SHOULDER CHARACTERS. 



The shoulder as here considered is the more or less rounded end 

 of the glume from the beak to the lateral margin, including the part 

 referred to by Koernicke and Werner (133), Hackel (101), and 

 others as side teeth. Scofield (173) applied the name shoulder to 

 this portion of the glumes. 



Considerable variation exists in shoulder width and shape in dif- 

 ferent varieties and also in different spikes of the same variety and 

 even among the glumes on a single spike. Although variable, they 

 are of considerable minor value in classification, 



