114 GRASSES OF IOWA. 



Awn stout, twisted, persistent Slipa. 2 



Awn straight, slender, or reduced to a mere point 



—Muhlenbetgia . 3 

 Flowering glume broad, awn slender,deciduous. Oryzopsis.* 



Flowering glume awnless Milium.*" 



Rachilla prolonged behind the palea in a pedicel-like extension, 



empty glumes minute Brachyelytrum.'- 



Flowering glume usually hyaline or membranaceous at maturity, at least 

 more delicate in texture than the empty glumes, grain loosely enclosed; 

 awn, when present, dorsal. 



Spikelets in a dense, spike-like panicle (some species of Sporobolus 

 may be found here.) 



Apex of empty glumes obliquely truncate, flowering glumes 



awnless Phleum." 



Empty glumes united at base, flowering glume awned on 



the back Alopecurus . 8 



Spikelets variously panicled (panicles spike-like in some species of 

 Sporobolus.) 



Grain not wholly covered by the flowering glume and palea; 

 pericarp separable from the grain, sometimes opening 



at maturity Sporobolus. 9 



Grain covered by the flowering glume and palea; pericarp 

 adherent. 



Palea one-nerved; stamen one Cinna. 10 



Palea two-nerved; stamens three. 



Callus naked or with a few very short hairs 



— Agrostis . " 

 Callus with a tuft of long hairs at the base. 

 Rachilla prolonged beyond the palet. 



— Calxmagrostis . 1S 



Rachilla not prolonged beyond the 



palet Calamovilfa . 13 



1. AR1STIDA. 



Aristida. L. Sp. PI. 82. 1753. Endlicher. Gen. PI. 88. Bentham and 

 Hooker. Gen. PI. 3: 1140. Hackel in Engler and Prantl. Nat. Pflanz. Fam, 

 II. 2: 45. /. 43. 



Curtopogon Beauv. Agros. 32. pi. 8. t. 7. 



Spikelets I -flowered, not jointed on pedicels. Outer glumes un- 

 equal, often bristle-pointed; the flowering glume tipped with three awns; 

 the palet much smaller. Otherwise much as in Stipa. Culms branch- 



