2 BULLETIN 406, U. S. DEPARTMENT OF AGEICULTURE. 
Johnson grass, is seen to bear several seeds (ripened spikelets) at- 
tached directly (sessile) at the nodes of the jointed axis (rachis) 
of the cluster. These are indicated in figure 2 by a, which shows 
them as occurring along only one side of the axis. Accompanying 
these fertile or grain-bearing spikelets, which constitute the greater 
part of the unhulled commercial seed, are several slender, sterile 
spikelets (b), each elevated on a stem or pedicel (d) which is attached 
with a fertile spikelet at a node of the rachis. It is to be noted that 
the terminal fertile spikelet is accompanied by two sterile spikelets 
with their pedicels. It is especially to be noted that in the figure 
each node and the apex of each pedicel are marked by a distinct cross 
line indicating the suture (e) at the articulation or junction of each 
rachis segment and of each pedicel with its spikelet. 
Fig. 1.— Seeds of Johnson grass (1) and Sudan grass (2). Hulled grains appear at the left of each group. 
(Natural size, from a photograph.) 
It is the normal habit of the seed clusters of Johnson grass at 
maturity to break apart at these sutures, thus providing for the fall 
of the seed. Each rachis segment and accompanying pedicel remain 
attached to a mature spikelet or unhulled seed. Terminal spikelets 
retain the two pedicels. The rachis segment and pedicel or the two 
pedicels may be referred to collectively as the appendages of the seed. 
In Sudan grass the terminal seed clusters in general structure are 
essentially the same as in Johnson grass. They differ, however, in 
being devoid of a suture at the nodes of the rachis and apex of the 
pedicels. In consequence, the seed fall does not uniformly result 
from separation at the articulation, but rather from the breaking of 
the rachis segments and pedicels at their weakest point, usually near 
the center (fig. 3, c). Most of the unhulled seeds therefore have a 
short stem (fig. 3, a). 
