Flora of the Palouse Rcgioji 15 



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

 stamens 1-6, usually 3: ovary i-celled, i-ovuled; styles 13, com- 

 monly 2 and lateral; stigmas hairy or plumose: fruit a seedlike 

 grain (caryopsis); endosperm starchy. 



Spikelets 1 or 2-flowered, when 2-flowered the upper fertile, the lower stam- 

 inate: rachilla jointed below the glumes and not extending be- 

 yond the flowers. Tribe 1. paniceae. 



Spikelets i-many-flowered: rachilla generally jointed above the empty 

 glumes (below in Nos. 30, 38 and 39) and in r-flowered spikelets 

 frequently extending beyond the flower. 



Spikelets in two rows forming a one-sided spike or raceme. 



Tribe 4. cheorideae. 

 Spikelets in two opposite rows forming an equilateral spike. 



Tribe 6. horde a e. 

 Spikelets on pedicels in panicles, spikes or racemes, not in rows. 



Spikelets with but 1 perfect flower which is terminal (except in 

 part of No. 32). Tribe 2. agrostideae. 



Spikelets with 2 or more perfect flowers (except that 1 is staminate 

 in Xos. 33 and 37). 

 Flowering glumes usually with a bent awn on the back, gen- 

 erally shorter than the empty ones 



Tribe 3. aveneae. 

 Floweriirg glumes unawned or with a straight awn from the 

 apex, generally longer than the empty ones. 



Tribe 5. kestuceae. 



Tribe i. PANICEAE. 



Spikelets single, in panicles or raceme-like sessile or panicled spikes: lower 

 empty glume short: lower flowering glume empty (flower abort- 

 ive) or with a staminate flower; upper one with a perfect flower. 



24. PANICUM. 



Tribe 2. AGROSTIDEAE. 



Flowering glume indurated at maturity, of firmer texture than the emptv 

 glumes and closely enveloping the grain. 

 Flowering glume with a 3-branched awn. 25. aristida. 



Flowering glume with a simple awn. 26. STIPA. 



Flowering glume hyaline or membranous at maturity: empty glumes coarser: 

 grain loose. 

 Spikelets in dense spikes or spike-like panicles. 

 Spikelets readily deciduous at maturity. 



Empty glumes not awned. 28. AEOPECURl'S. 



Empty glumes awned. 30. poeypogox. 



Spikelets not deciduous: empty glumes persistent. 



27. I'HI.Kl'M. 



Spikelets variously panicled; panicles not spike-like. 



Flowering glume 1-, rarely 3-nerved: seeds loosely enclosed in the 

 pericarp, which opens readily at maturity. 



29. SPOROBOEl'S. 

 Flowering glume 3-5-nerved: seed adherent to the pericarp. 



Callus with a tuftoflong hairs atthebase. 32. cai.amagkostis 

 Callus naked. 31. agrostis. 



