CHAPTER XX 

 TRIBE VIII. AGROSTIDE^ 



A LARGE tribe of about 50 genera inhabiting more 

 especially the temperate and cooler regions of the world. 

 Spikelets 1 -flowered (the rachilla prolonged as a stipe 

 behind the palea in a few genera) usually perfect, arranged 

 in open, contracted or spike-like panicles, but not in 1 -sided 

 spikes or racemes. The spikelets are jointed with the 

 pedicel in a few genera, and fall off entire (Alopecurus, 

 Cinna, Polypogon, Lycurus, Limnodea). The palea is 

 usually 2-nerved but in Cinna it appears to be 1-nerved, 

 the 2 nerves lying close together. In some species of 

 Agrostis the palea is a small nerveless scale or is wanting. 

 In some genera the floret is raised slightly from the glumes 

 on a hard stipe, the short internode of the rachilla. This 

 remains attached to the floret at maturity as a hard point 

 and is called the callus. This callus is pronounced in 

 Stipa and Aristida and less so in Oryzopsis, Muhlen- 

 bergia and a few other genera. In some species of Calama- 

 grostis the short callus bears numerous silky hairs as long 

 as the floret. 



KEY TO THE GENERA OF AGROSTIDE.E 



A. Lemma indurated at maturity, firmer than 

 the glumes, closely enveloping the caryopsis 

 and usually the palea, awned (except in 

 Milium) from the tip, or mucronate (some 

 species of Muhlenbergia) . 

 B. Awn trifid (the lateral awns sometimes 



short, rarely wanting) ARISTIDA 



BB. Awn simple. (Par. 229). 



(196) 



