56 BULLETIN 981, U. S. DEPARTMENT OF AGRICULTURE. 
it was impossible to ascertain by seed inspection whether it was 
adulterated with Johnson grass seed. F. H. Hillman, after a critical 
study of the seeds of the two grasses, published (11) complete instruc- 
tions for their identification. The method is based chiefly on the 
character mentioned by Oakley, that of the attachment of the seed to 
the rachis branch, but this was amplified and explained by drawings 
in a way which now makes it possible, at least for a trained seed 
analyst, to identify the two seeds with reasonable certainty. (Figs. 
24 and 25.) 
Fig. 23.—Seeds of Johnson grass (1) and Sudan grass (2). Hulled grains appear at theleft ofeach group. 
(Natural size, from a photograph.) 
TaBLE XIX.—Distinguishing characters of the seeds of Sudan grass and Johnson grass. 
Length of seeds. Prevailing color. 
Kind of seeds. a ae A a 
Unhulled. | MHulled. Hulls. Hulled seeds. 
| | 
| Inches. | — Inches. 
SUGaN LASS ..-ee- sn- eeemce 0.18 to 0.25 | 0.13 to 0.18 | Straw or light tawny, | Light reddish brown. 
| some reddish and 
| some blackish 
brown. 
LGHNSOMPELASS oe ee eee eel 0.15 to 0. 25 
bo 
0.08 to 0.12 | Blackish brown, some | Dark reddish brown. 
reddish and some 
straw color. 
Character of the— 
Sng aiheerik. Apex of the seed | Shape of the hulled 
Attachment of | | appendages. — 
seeds. Embryo. 
SUGAaATPTASS =o... Sask. No distinct suture | Relatively large. | Jaggedly broken, | Elliptical in out- 
or scar tissue; | notexpanded. | line. 
portion ofrachis 
segment usually | 
| _ adhering. 
Johnson grass. ......... Distinct suture or | Smaller and nar- | Smooth, expand- | Usually oval or 
scar; usually no; rower than that ed, cup shaped. oval-elliptical. 
rachis segment of Sudan grass. | 
adhering. | 
