[8 



POACEAE. 



Family 15. POACEAE. Grass Family. 



Annual or perennial herbs, rarely shrubs or trees; stems (culms) 

 nerally hollow; nodes closed; leaves 2-ranked, sheathing, the 

 sheaths usually split to the base on the side opposite the blade; 

 scarioua or membranous appendage (the ligule) borne at the 

 opening of the sheath, rarely obsolete; inflorescence a spike, a 

 raceme or a panicle, consisting of spikelets composed of two to 

 many 2-ranked imbricated bracts; the lowest two {glumes) 

 without flowers or rarely wanting; one or more of the upper 

 (lemma) containing in its axil a flower, which is usually enclosed 

 by a bract-like, generally 2-keeled, awnless organ (palea) opposite 

 the g hi me and with its back toward the axis {rachilla) of the 

 spikelel ; lemma sometimes bearing an indurated thickening 

 i callus) at the base; flowers perfect or sometimes monoecious or 

 dioecious, subtended by 1-3 minute hyaline scales (lodicules) ; 

 stamens 1-6, usually 3; ovary 1-celled, 1-ovuled; styles 1-3, 

 commonly 2 and lateral; stigmas hairy or plumose; fruit a seed- 

 like grain (caryopsis) or rarely a utricle; endosperm starchy. 



Spikelets with one perfect flower. 

 Spikelets with only one flower. 



Rachilla jointed below the glumes which fall 



with the seed. Tribe 1. Paniceae. 



Rachilla jointed above the glumes which do 

 not fall with the seed. 

 First two lemmas empty, variously modi 



fied, the third with a flower. 

 Firs! Umma flower-bearing. 



Spikelets crowded in two rows in one- 

 sided spikes. 

 Spikelets not in one-sided spikes. 

 Spikelets in two opposite rows. 



Hordeum in Tribe 7. 

 Spikelets not in two opposite rows. Tribe 3. 

 Spikelets with a staminate or neutral flower in 

 iddition to the perfect one. 

 Rai liilla jointed below the glumes which fall 



with the seed. 

 Rai hilla jointed above the glumes which do 

 not fall with the seed. 

 Imperfect flower below the perfect. 



, , „ Arrhenatherum in Tribe 4 



impenecl flower above the perfect. 



■ • , Holcus in Tribe 4 



s j'ik. I. ts with two or more perfect flowers 



v '" 1 «"le on the rachis; inflorescence a 



Ke. 



Tribe 2. Phalarideae. 



Tribe 6. Chlorideae. 



Hordeae. 

 Agrostideae. 



Tribe 1. Paniceae. 



Aveneae. 



AVENEAE. 



pedicelled; inflorescence a panicle, 



Tribe 7. Hordeae. 



