PANICLE CHARACTERS OF SORGO 17 
either the prevailing or the average form as the typical one, or one 
of the groups may be so defined as to include a range of forms rather 
wider than the other groups. 
It is often necessary in order to distinguish between certain 
varieties to know in some detail how they differ, and this can 1 
be shown by describing them completely and indicating the 
forms of spikelet which each variety presents. On account of such 
fluctuations in form, it is, of course, always desirable in making 
determinations to examine an entire panicle, or, better, several 
panicles of the variety, in order to be sure of the forms represented. 
All ovate forms are not identical ; neither are all the obovate 
forms. Such terms do not therefore indicate very definite shapes. 
Hackel (<§, pp. 499-520) made these terms more definite by indicating 
the point in the length at which the breadth was greatest. It is 
also possible to describe more accurately intermediate forms by 
making distinctions between such compound terms as ovate-elliptic 
and elliptic-ovate, the former being considered a shape more elliptic 
than the latter, being an elliptic shape occasionally or somewhat 
ovate, and in like manner the latter being considered a nearly ovate 
but somewhat elliptic shape. 
The form of the spikelets in the unexpanded panicle and also be- 
fore the caryopses develop to such size as to cause the glumes to 
spread, or before they become exerted from the glumes, differs more or 
less from their form in the mature panicle. The enlarging caryopsis 
tends to make the spikelet broader and in some cases to make it 
more obovate. The opening of the glumes, on the other hand, tends 
to make the outline more ovate in form, because one of them is often 
folded back in the process of opening. 
Spikelets of the several varieties occasionally show slight differ- 
ences in thickness and in their form laterally, both these characters 
being much influenced by the extent to which the glumes open. 
They are relatively less important than the foregoing characters. 
The form of the apex differs also. Most commonly it is acute, but 
in some varieties it is obtuse, and in others occasionally it is some- 
what acuminate. 
FORM OF THE GLUMES 
The outline presented by the glumes viewed dorsally is usually sim- 
ilar to that of the spikelet, and the range of forms in glumes is there- 
fore approximately the same as in spikelets. From a lateral view the 
glumes are usually either convex or boat shaped, but the first is 
sometimes somewhat flattened. In some varieties the lower two- 
thirds or three-fourths of the first glume is convex, and the portion 
adjacent to the apex is somewhat flattened, and in those kinds in 
which the glumes are strongly obovate the upper portion is often 
very convex and the lower less so. The second glume is commonly 
more or less keeled, and the first usually has a coarse or keellike 
nerve on each side, this tending to alter the form more or Less 
cording to its coarseness and prominence. One or both glumes are 
frequently longitudinally wrinkled or puckered at the base. 
Both glumes are usually either inflexed or incurved on the side, 
the degree varying somewhat. As the spikelet opens, the glumes 
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