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Journal of Agricultural Research voi. xxm, no. 3 
L. {Sorghum halepensis Pois) and Sudan grass as subspecies of the same, 
which he calls Holcus halepensis sudanensis (Piper) Hitchcock {Andro- 
pogon halepensis sudanensis Piper). The very close taxonomic relation¬ 
ship of the two forms increases the interest which attaches to the marked 
physiological differences between their seeds. 
STRUCTURE OF THE FRUITS AND CARYOPSES OF JOHNSON GRASS 
I. EXTERNAL APPEARANCE 
Oakley (25), Vinall (jo), and Youngblood and Conner (32) discussed 
the external appearance of the fruits of Johnson grass in comparison with 
those of Sudan grass. Hillman (77) later described in detail the fruits of 
these two kinds of grass, both with the scales on and with the scales 
removed. 
Figure I, adapted from figure 4 in Hillman’s paper, shows the external 
characters of the fruit of Johnson grass. The unhulled fruit or spikelet 
(A) is about 0.2 inch long and a little less than one-half as wide as long. 
It bears at its proximal end a smooth regular scar (a). The caryopsis (B) 
with its hyaline lemma is inclosed in two, straw-colored to black overlap¬ 
ping scales, the glumes. The outer scale, or lower glume, is convex and 
spear-shaped (A, I). 
Pig. i.— Johnson grass spikelets and caryopses: A, Unhulled spikelets, showing convex outer surface at 
I and flat inner surface at II; B, caryopses, showing scar of the spikelet (a), appendages of the spikelet 
(b, b), upper glume (c), overturned edge of the lower glume (d), broken ends of the glumes (e), depressed 
area where the pericarp extends over the hilum (f), scar of the caryopsis (g), and embryo (h) 
The inner scale, or upper glume (c), is nearly flat, but slightly keeled. Its 
outer edge is inclosed by the overturned edge of the outer scale (d). The 
flattened inner side of the unhulled fruit usually bears two appendages, a 
rachis segment and the pedicel of a sterile spikelet (b, b). The distal 
ends of the glumes frequently are jaggedly broken (e) in many of the 
fruits of commercial lots. We have found that sufficient rubbing to 
cause a large amount of such breakage or even the very careful cutting 
away of the distal half of the glumes increases the germination of dormant 
lots even if none of the caryopses are removed from the scales. 
The caryopsis (fig. 1, B) is about three-fourths as long as the unhulled 
fruit, oval or oval-elliptical in shape, dark reddish brown in color. The 
side of the caryopsis which was next to the outer scale is nearly flat and 
bears at its proximal end a small, roundish, very dark, and somewhat 
depressed area (f) where the pericarp extends across the hilum. At the 
extreme proximal end is the scar of the caryopsis (g). The side which 
was next to the inner scale is somewhat convex. At its proximal end is 
located the fairly large embryo (h), the position of which is clearly 
marked by a somewhat lighter color than that of the rest of the caryopses. 
