20 BULLETIN 1386, L. S. DEPARTMENT OF AGRICULTURE 
varieties in which the second glume is bent more than the first, this 
resulting from the caryopsis developing more in that direction than 
the other. 
VENATION 
The first glume is commonly more strongty nerved than the sec- 
ond, and in the greater number of varieties one of the nerves on 
each side in the first glume, usually the second nerve from the edge, 
is coarser than the others, is sometimes keellike, and is also usually 
finely scabrous-hispid above. There are rather wide differences be- 
tween varieties in regard to coarseness of the nerves and their 
length from the apex of the glume downward, the latter being closely 
correlated with the amount of thickening in the glume. The points 
at which the nerves end are always more or less indefinite, but their 
length may be approximately expressed in comparison with the 
length of the entire glume. Differences in regard to coarseness, 
though sometimes very evident, are still more difficult to denote and 
these differences can usually be expressed only in general terms. 
• The nerves on the sides, especially the keellike nerves, frequently 
extend farther downward than those in the middle. In one or more 
varieties these lateral nerves are commonly apparent from the 
apex to the base of the glume, while the remainder extend for about 
three-fourths or four-fifths the length. In certain other varieties 
the lateral nerves arc visible for about one-third or one-ball' and 
the middle nerves for one-fifth or two-fifths the length. 
The approximate number of nerves in the first glume has been 
indicated by some writers, including Hackel (#, pp. l , . ,( -> 520) and 
Stapf (16, pp. 104 154). To count them in mature spikelets is dim- 
cult, on account of the indistinctness of the nerves and the necessity 
of magnifying them. The ranges found within many varieties are 
also somewhat wide. The range for the entire sorgo group ap- 
parently extends from about 6 to about 18 nerves. Differences be- 
tween certain varieties in the mean number and the range are ap- 
parent, the range in certain of them being from 6 or 7 to about 12, 
in others from about 12 to about L8, there also being an intermedi- 
ate class in which the mean number is approximately 12. 
The colors of glumes vary from pale yellow to deep black, several 
shades of brown being encountered, including reddish browns, the 
color being intensely reddened in one or more varieties. Some of 
the glumes in certain varieties are sometimes grayish or purplish. 
(Humes are frequently somewhat mottled and often considerably 
lighter at the apices. Variations in color within types and also 
within panicles occur, panicles in which the spikelets are in the main 
black sometimes Inning some drab, blue-black, grayish, or purplish 
spikelets. The browns also vary, particularly in the intensity of 
yellow or red (dements. Approximately the average color in each 
of the four types is shown in Plate XIII. Color is not only often 
the most evident distinguishing mark, but between certain lines it 
constitutes the chief describable difference by which the varieties can 
be separated, being a character which has been used in keys and 
descriptions by nearly all writers. 
