87 



Tribe IX.— AVENEJE. 



Spikelets 2-to several-flowered; outer empty glumes usually 

 longer than the 1st floral glume; one or more of the flowering 

 glumes awned on the back or from between the teeth of the bifid 

 apex; awn usually twisted or geniculate; *the callus, and usually the 

 joints of the rachilla, hairy. 



A tribe comprising 23 genera and over 300 species, 

 widely distributed in the temperate regions of both 

 the Old and the New World, particularly abundant 

 in South Africa and Australia, a few extending beyond 

 the arctic circle. 



Several of the species are of economic value as for- 

 age plants. Tall meadow oat-grass (Arrhenatherwn 

 elatius (L.)) and Velvet grass or mesquite, as it is 

 known in Oregon and Washington, both introduced 

 from Europe, are grasses of much agricultural value, 

 especially the first named. Tufted hair-grass (De- 

 schampsia ccmpitosa (L.) ), a common grass in the 

 Rocky Mountain region of the Northwest, is of some 

 local value as a forage plant, especially for low wet soils. 

 Cultivated oats, Avena sativa, used largely in the South 

 and on the Pacific coast for pasturage and hay, and gen- 

 erally as a grain or cereal, is the best-known example 

 of this tribe. 



KEY TO THE GENERA OF THE AVENE.E. 



1 . Rachilla not prolonged behind the palea of the upper floret, 

 both flow T ers hermaphrodite 66. Aira 



1. Rachilla prolonged; spikelets 2-to several-flowered; when 



2-flowered, one of the flowers usually staminate or imperfect. 2 



2. Spikelets articulated with the pedicels below the outer glumes; 



the first floret hermaphrodite and awnless, the second stami- 

 nate and awmed '_ _ 65. Holcus 



2. Spikelets not articulated with the pedicels below the outer 



glumes - 3 



3. Awns dorsal 4 



3. Awns from between the teeth or divisions of the flowering glume 

 and flattened near the base 72. Danthonia 



