CLASSIFICATION OF AMEEICAN WHEAT VARIETIES. 
47 
in Figure 18. In short brush the hairs are less than 0.5 mm. long, 
in midlong brush from 0.5 to 1 mm. long, and in long brush more than 
1 mm. long. 
All durum wheats and some varieties of common wheat, such as Bobs 
and Prelude, have a short brush. A few very long hairs may be 
present in a short brush. Humpback and Mealy are varieties of 
common wheat having a long brush. Both the size and the length 
of the brush are very constant characters, probably the most constant 
kernel characters aside from color and size. In machine thrashing, 
part of the hairs of the brush frequently are removed. The brush 
area of some varieties is here described as "collared" (Fig. IT, d). 
Cobb {71) referred to this as an abrupt margin. This refers to the 
presence of a distinct raised collar or flange of bran along the margin 
of the brush area. This is most noticeable on shrunken kernels, but 
is very distinct on normal kernels of a 
few varieties, such as Goldcoin and 
Champlain. 
PHYSIOLOGICAL CHARACTERS. 
Several characters of wheat varieties 
of interest to growers can not be observed 
in a morphological examination. These 
differences are of a physiologic a.1 or in- 
ternal nature. They are of great eco- 
nomic importance, but are of little value 
in classification. Following the descrip- 
tions of many of the varieties, therefore, 
certain of the physiological characters here mentioned are considered. 
The leading physiological characters of importance in wheat 
varieties are productivity, milling and bread-making values, resist- 
ance to low temperatures, and resistance to diseases. 
PRODUCTIVITY. 
A comparison of yield is of value only in comparing different vari- 
eties of wheat grown under identical conditions, as side by side, on 
identical soil, or in one locality in the same season. Under certain 
conditions it is possible for almost any variety to outyield all others, 
and consequently an expression of yield is of little taxonomic im- 
portance unless definite experiments at several points show a variety 
to be significantly high or low in yield. Koernicke and Werner {133) 
recorded the yields of the varieties grown at Poppelsdorf in the de- 
scription of each variety. In the present work the writers have men- 
tioned productivity or yield following the descriptions of only a few 
varieties, which experiments have shown to be distinctly high or low 
in yield. 
a h c 
Fig. 18. — Brush length: a. Short; 
t, midlong; c, long. (Natural 
size and enlarged 3 diameters.) 
