CLASSIFICATION OF AMERICAN WHEAT VAMETTES. 27 



color is usually most apparent on the peduncle, or uppermost inter- 

 node supporting the spikes, but often continues downward to the 

 sheaths of the lower leaves. 



Those varieties here described as having white stems may have a 

 stem color ranging from a cream to a golden yellow. Few, if any, 

 have stems which are truly white or with an absence of color. 



The varieties classed as having purple stems may have a stem rang- 

 ing in color from a pale violet to a dark purple. In some varieties 

 this coloring may occur only in a short portion of the peduncle. It 

 sometimes does not occur in the peduncle and is present only in the 

 sheaths. As previously stated, under some conditions it may not 

 appear at all in a variety where it normally is present. The exact 

 cause and nature of this coloring have not been worked out by the 

 writers. It is probable that different quantities of moisture, heat, and 

 light influence the color development. Koernicke and Werner used 

 color differences in describing many of the varieties with which they 

 worked. Heuze (112, p. 54) pointed out the two contrasting charac- 

 ters, which he called white and reddish. Color always has been con- 

 sidered of minor importance in classification, however. 



STRENGTH OF THE STEM. 



The strength of the stem usually is an important economic factor. 

 In many localities it is one of the most serious problems in wheat 

 production, as many varieties are likely to lodge under conditions of 

 excessive moisture. All varieties here discussed are classified into 

 three groups, having weak, midstrong, or strong stems, respectively. 



Stems classed as weak are also usually slender, with very thin 

 walls. Varieties with such stems have a greater tendency to lodge, 

 which in turn causes harvest losses and increases the cost of harvest- 

 ing. The successful cultivation of weak-stemmed varieties usually is 

 limited to semiarid or arid regions. 



The varieties classed as having midstrong stems will not lodge 

 under conditions favorable for wheat production. In this class are 

 included the greater number of American varieties. A considerable 

 variation exists within this group, and in humid sections varieties 

 here described as having midstrong stems might more properly be 

 classed as weak. In arid sections certain of these stems might more 

 properly be classed as strong. 



The varieties here described as having strong stems are those that 

 will not lodge readily under excessively humid conditions. Only by 

 a severe rain, hail, or wind storm can the stems of these varieties be 

 bent or broken down. Comparatively few of the cultivated American 

 wheats come in this class. Of these, the club wheats are of most 

 importance. 



