57 



Tribe VIIL— AGROSTIDEjE. 



Spikelets all hermaphrodite, 1-flowered with 3 glumes, the first 

 2 empty (very rarely wanting) , usually as long as or exceeding 

 the 3d or floral glume; rachilla sometimes prolonged behind the 

 palea into a naked or plumose bristle. Palea two-nerved (one- 

 nerved in Clnna) , nerveless, or (in some Agrostis species) wanting. 



This is, next to the Festucem, the largest tribe in the 

 order, numbering 700 species arranged in 46 genera. 

 The species are distributed throughout all the tem- 

 perate and colder regions of the world and many occur 

 within the Tropics. The genus Agrostis, from which 

 the tribe derives its name and from which comes the 

 word u agrostologist," has about one hundred species, 

 found in all parts of the world, especially in the north 

 temperate zone. Some of our most important meadow 

 grasses — notably Herd's -grass and timothy — belong to 

 this tribe. 



KEY TO THE GENERA OF THE AGROSTIDE.E. 



1. Flowering glumes awned or mucronate-pointed 2 



1. Flowering glumes awnless 19 



2. First empty glume with two to three awns, inflorescence a 



spike-like panicle 45. Lycurus 



2. First empty glume with a single awn or awnless 3 



3. Awn of the flowering glume terminal or from between the 



teeth of the bifid apex 4 



3. Awns dorsal 13 



4. Awns 3-branched or trifid, the lateral divisions sometimes 



very short 39. Aristida 



4. Awns simple or unbranched 5 



5. Awns articulate with the apex of the flowering glume 6 



5. Awns not articulate with the glume 8 



6. Awns usually long, geniculate and twisted below, persistent or 



but tardily separating from the narrow and rigid flowering 

 glume, which is tightly rolled around the grain in fruit; 



callus acute 40. Stipa 



6. Awns short, caducous or falling off soon after flowering 7 



