22 
Colorado Agricultural College 
The palet is never awned (bearded), the glumes and lemma are 
inserted on the rachilla, and the palet on a very short flower stalk 
(pedicel). The ovary of the grass flower contains a single ovule, 
which when fully developed or mature is a one-seeded grain-like 
fruit (caryopsis). The seed proper is enclosed by the pericarp 
(ovary wall) which is firmly attached to the seed coat^ 6 )- 
There is usually an abundance of endosperm present. The germ 
(embryo) is located at the base of the grain on the side opposite 
the hilum (scar at the point of attachment of the grain to the 
stalk). 11 • 1 1 
Considering the grains (fruits) of grasses collectively, there 
are two classes in which all grass grains may be placed : ( 1 ) Grains 
free at maturity, and ( 2 ) grains adherent to the palet and lemma 
at maturity. 
KEY TO GENERA 
1 . . Cenchrus 
2 . . Panicum 
Seeds adherent (adnate) at maturity 
Seeds enclosed by a persistent involucre armed with barb- 
like spines 
Seeds not enclosed in a persistent involucre armed with 
barb-like spines , ! 
Seeds awnless 
Margins of lemma inrolled along entire length . . . 
Margins of lemma not inrolled along entire length 
Margins of lemma inrolled except at the tip 
Lemma shiny, smooth S. .Echinochloa 
Lemma distinctly roughened transversely i. .Setaria 
Margins of lemma not inrolled 5 . . Syntherisma 
Seeds awned 
Rachilla absent ; lemma bearing three awns, two lateral 
ones united at the base — seeds scarcely wider than 
the awn <>. .Aristida 
Rachilla present 
Rachilla prolonged behind palet as an awn.... 
Rachilla not prolonged behind palet as an awn 
Awn dorsal 
Awn arising from a hyaline (transparent) lemma 8. 
Awn arising from an indurated (hardened) 
lemma 9. .Auena 
Awn not dorsal 
Palet completely enclosed by the lemma ; lemma 
indurated ; a hard sharp point at base of 
seed SHpa 
Palet not completely enclosed by the lemma 
Lemma with a dorsal ridge (midrib) 
Dorsally ridged throughout 11. .Bromus 
Dorsally ridged at the tip only 12 . .Agropyron 
Lemma without a dorsal ridge (midrib) 
Veins of lemma 3-7. distinct converging at 
apex , 
Veins of lemma obscure throughout... 
Seeds free at maturity 
Seeds cylindrical, pointed at both ends 
Seeds .4-.G mm. long 
Seeds .5-1.5 mm. long, often with a characteristic black 
mark at the base... .SporoMus 
Seeds not cylindrical: seeds shiny, turbinate in shaiie \ i . . Pamculai ui 
7. .Hordeum 
.Andropogon 
, 13 . . TjoHum 
14. .Elymus 
15. . E ragrostis 
