DISTINCTIONS IN CULTIVATED BAKLEYS. 35 
ferent areas. The diameter of the culm is not serviceable, because 
nearly related barleys have culms of approximately the same size. 
The thickness of the walls of the culm is a note with a large experi- 
mental error and therefore of questionable utility. 
The degree of exsertion of the spike is sometimes a varietal char- 
acter but is not often useful. 
The number of culms per plant is to some extent a varietal char- 
acter, but selections are so affected by season and location that it is 
very difficult to use. The width of the leaves is useful in group 
distinctions and sometimes in varietal separations. The length of 
the leaves is much less dependable, and is serviceable only in rather 
extreme types, The number of leaves varies with the groups, but 
usually closely related strains possess approximately the same num- 
ber of leaves. 
The density of the spike may easily be made the basis of many 
separations. Often varieties that show no other differences are 
widely dissimilar in density. The density of a selection varies 
somewhat with season and location, but the mean is always sharply 
defined and the fluctuations more or less parallel. In some strains 
all spikes conform closely to the mean ; in others the range is greater. 
This seems to be a varietal character and is constant even when the 
plantings are made* under widely varying climatic and soil conditions. 
The established taxonomic groups based on relative fertility were 
found to be invariable under all extremes of American climate. 
The natural varieties in the deficiens group of Abyssinian barleys 
seem more extensive than most classifications have indicated. From 
barleys of this s?.me region a group with a peculiar habit of floret 
abortion has been isolated. 
The length and the width of awns vary, but they are so correlated 
with other taxonomic characters that they are seldom useful in close 
separations. 
The tenacity of the awn is frequently a varietal character unaf- 
fected by location or season. 
The character of the basal bristle has been found to be stable 
under American conditions. 
The toothing of the inner pair of dorsal nerves is much more 
variable, but the variation is usually within definable limits. 
The length of the kernel, while influenced by climate, is a varietal 
character. The lateral and dorsoventral diameters of the kernel are 
varietal characters to some degree, but they are so influenced by con- 
ditions of growth as to become confusing in most instances. 
The composition of the grain is a varietal character, but it is one 
dominated by climate. 
There are two coloring materials in barley: One, anthocyanin, is 
red in its acid and blue in its alkaline condition : the other, a melanin- 
