26 BULLETIN 1074, XJ. S. DEPARTMENT OF AGRICULTURE. 



Grantham (98) showed that tillering is a varietal characteristic to a 

 limited extent. He also showed that — 



Since the number of tillers a wheat plant produces is dependent upon so 

 many environmental conditions a number of observations must be made in 

 order to establish in which degree this tendency is exhibited. For this reason 

 it is difficult to classify varieties closely as to their tillering habit. 



The degree of tillering, therefore, is of little value for classification 

 purposes and is not used in the descriptions. A few varieties, such 

 as Turkey, usually have a large number of culms per plant, while 

 durum varieties have comparatively few. 



HEIGHT OF THE PLANT. 



The height of the plant also is often an important economic factor 

 in wheat production, because it may determine the method or ease of 

 harvesting. Height is measured from the surface of the ground to 

 the tip of the spike, not including the awns of awned varieties. In 

 regard to height, all varieties of wheat have been placed in the three 

 classes — short, midtall, and tall. These are characters of minor 

 value for classification and are used only for separating or dis- 

 tinguishing otherwise closely related varieties. The principles gov- 

 erning the grouping of varieties as early, midseason, and late apply 

 here also. As an example, under California conditions wheats from 

 12 to 36 inches in height would be classed as short; wheats from 24 

 to 48 inches in height would be called midtall, and wheats from 36 

 to 60 inches high would be considered tall. In most other sections of 

 the country these differences would not be as great. In order to use 

 the height of the plant as a character, the height of certain varieties 

 must be determined and used for comparison. 



STEM CHARACTERS. 



There are three characters in the stem of wheat varieties which 

 are useful in classification, namely, height, color, and strength. 

 Height already has been considered as a plant character. 



COLOR OF THE STEM. 



All varieties of wheat are here classified as having white or purple 

 stems. The colors of the stem and the variations that exist are shown 

 in Plate III, Figure 1, a and b. These characters are of minor im- 

 portance in classification, for in many localities and in some seasons 

 the purple color common to a large number of wheat varieties does 

 not become apparent. This often is the case under conditions of ex- 

 treme drought and also under conditions of excessive moisture. Un- 

 der favorable conditions, however, this stem color is very apparent 

 during a week or 10 days in the ripening period. When apparent, the 

 color differences are very useful in distinguishing varieties. The 



