BULLETIN 406, U. S. DEPARTMENT OF AGRICULTURE. 
Fig 
DISTINGUISHING CHARACTERS OF THE SEEDS OF JOHNSON GRASS. 
Jolmson grass seeds in the hull (fig. 4, 1) vary in length from fifteen 
one'-hundredths to twenty-two one-hnndredths of an inch. Most of 
the seeds have a smooth, 
rounded, and light- 
colored scar at the base. 
The appendages of the 
seed (fig. 4, I) are mostly 
||2 entire, expanded, cup 
\My d \V%w shaped, and smooth at 
the apexes, correspond- 
ing with the scar at the 
base of the seed. The 
uniformly smooth border 
of the expanded, cup- 
shaped apex, together 
with the smooth seed scar, results from the normal separation of the 
seed along a definite suture. 
The prevailing color of mature seed hulls is 
blackish brown. Many seeds are partially or 
wholly reddish. Some are straw colored. A few 
are tawny or light brown. 
The hulled grains (fig. 4, 2) vary from eight 
one-hundredths to twelve one-hundredths of an 
inch in length. They usually are oval, sometimes 
oval-elliptical in outline, the embryo end tending 
to be the more pointed. The color is dark reddish 
brown. They are noticeably smaller and darker 
colored than those of Sudan grass and have a 
relativelv narrower embryo (fig. 4, d). 
Johnson grass seeds . enlarged. Unhulled seeds , spikelets 
(1); hulled grains (2): a, a. Scar of the hull; 6, b, appendages of 
the seed with expanded, cup-shaped apexes; c, scar of the grain; 
d. emhryo. 
APPARENT EXCEPTIONS TO THE DISTINGUISHING 
CHARACTERS DESCRIBED. 
Conflicting conditions arise from exceptions in 
the manner of the fall of the seeds of Sudan grass 
and Johnson grass. 
Occasional Sudan grass seeds have no stem at 
the base, but the scar usually is irregular or jagged, 
owing to the absence of a definite suture. Like- 
wise, some seeds have one or both appendages 
unbroken, with expanded and occasionally cup-shaped apexes. The 
size of the seed, together with the size, form, and color of the grain, 
should suffice to distinguish the seed from that of Johnson grass. 
Fig. 5. — Stem-bearing seeds 
of Johnson grass, enlarged: 
(1) A seed in which the 
stem (a) is a portion of a 
rachis segment. The sut- 
ure (b) at the junction of 
the stem and seed is evi- 
dent. (2) A seed (the 
lowest of the cluster) in 
which the longer stem (c)is 
a part of the cluster branch. 
No suture occurs at the 
junction (d) of the branch 
and the first rachis seg- 
ment (c). The opposite 
side of such a seed shows 
the suture, as at b. 
