32 BULLETIN 1074, U. S. DEPARTMENT OF AGRICULTURE. 
lish density classes of rather indefinite limits. In this way allow- 
ance was made for the varying conditions. ‘The density classes were 
finally fixed as lax, middense, and dense by determining the number 
of millimeters occupied by 10 internodes of the rachis measured in 
the center of the spikes. By this method spikes are classed as lax 
when 10 internodes occupy from 50 to 75 mm., as middense when 10 
internodes occupy from 35 to 60 mm., and as dense when 10 inter- 
nodes occupy from 20 to 45 mm. The greater number of varieties 
are included in the middense class, which, according to the above 
measurements, overlaps both the dense and lax classes by two-fifths 
of their entire range. 
POSITION OF THE SPIKE. 
The position of the spike at maturity is often distinctly different 
in different varieties. All spikes are here described as erect, inclined, 
or nodding. Heuzé (//2) used essentially these same distinctions 
in describing his varieties. 
Those varieties described as having erect spikes mature with the 
spike in an approximately vertical position. The spikes of these 
varieties seldom, if ever, are inclined more than 15 degrees from the 
vertical at maturity. Spikes of varieties which are described as 
inclined usually mature at an angle of approximately 15 to 45 de- 
grees from the vertical, but sometimes are nearly erect, and under 
some conditions will become slightly nodding. The majority of 
wheat varieties come within this class. Varieties which are described 
as having nodding spikes usually mature with the spike in a droop- 
ing position, the apex of the spike being lower than the base. Spikes 
of such varieties sometimes are only inclined if they are not well 
filled with grain when ripe. 
GLUME CHARACTERS. 
The unit of the spike is the spikelet. It consists of several flowers 
or florets attached alternately to opposite sides of a central axis or 
rachilla. These flowers, three to five in number, are subtended by 
two empty scales, called the glumes, the keel of which terminates in 
a tooth or beak. Each floret consists of a flowering glume, called 
the lemma, and a thin 2-keeled glume called the palea. These two 
glumes inclose the sexual organs. The lemma incloses the back, 
dorsal, or outer portion, of the mature kernel and in the awned va- 
rieties terminates in an awn. The lemma itself is of little or no 
use in classification. The palea protects the inner or crease side of 
the kernel. It differs from the lemmas in having its back, instead of 
its face, toward the rachilla or axis of the spikelet. Like the 
lemmas, it is not used in distinguishing varieties. The glumes, how- 
ever, are much used. 
