FLOWERING PLANTS AND FERNS OF ARIZONA 107 



27. TRISETUM 



Tufted perennials with flat leaf blades and open or spikelike, usually 

 shining panicles; spikelets 2- or 3-flowered; rachilla prolonged beyond 

 the upper floret, usually villous; glumes acute, the second a little 

 longer than the first; lemmas 2-toothed, bearing from just below the 

 cleft a bent exserted awn. 



Key to the species 



1. Plants annual; spikelets disarticulating below* the glumes; rachilla pubes- 

 cent 1. T. IXTERRUPTUM. 



1. Plants perennial; spikelets disarticulating above the glumes; rachilla villous 

 (2). 

 2. Panicles dense, spikelike, more or less interrupted below. 2. T. spicatum. 

 2. Panicles open, rather densely flowered but not spikelike- 3. T. moxtaxum. 



1. Trisetum interruptum Buckl., Acad. Xat. Sci. Phila. Proc. 1862: 



100. 1862. 

 Santa Rita Mountains, Pima County (Pringle in 1884). Dry or 

 moist open ground, Texas, Colorado, New Mexico, and Arizona. 



2. Trisetum spicatum (L.) Richt., PL Eur. 1: 59. 1890. 



A ira sp ica t a L . , , Sp . PI . 64 . 1753. 



Trisetum subspkatum Beauv., Ess. Agrost. 88, 149. 1812. 



Summit of Baldy Peak (Apache County), San Francisco Peaks 

 (Coconino County), alpine slopes and meadows, 10,500 to 12,000 feet. 

 Arctic America, south to Connecticut, Pennsylvania, Minnesota, and 

 in the mountains to New Mexico, Arizona, and California; high 

 mountains of Mexico and South America; alpine regions of the Old 

 World. 



3. Trisetum montanum Vasey, Torrey Bot. Club Bui. 13: 118. 



1886. 

 Pinaleno Mountains, Graham County, 9.500 feet {Kearney and 

 Peebles 9970). Mountain slopes and meadows, Colorado, Utah, New 

 Mexico, and Arizona. 



28. DESCHAMPSIA. Haikgrass 



Annuals or perennials with narrow or open, shining panicles; 

 spikelets 2-flowered, the hairy rachilla prolonged beyond the upper 

 floret, sometimes bearing a rudimentary floret; glumes equal, acute; 

 lemmas thin, erose-truncate with a straight or bent and twisted awn 

 from or below the middle. 



Key to the species 



1. Plants annual; panicle open, the stiffly ascending capillary branches usually 

 in 2's 1. D. DANTHONIOIDES. 



1. Plants perennial; panicle narrow or open, the slender branches appressed or 



drooping (2). 

 2. Glumes usually longer than the florets; panicle usually narrow, as much as 

 30 cm. long, the branches appressed; leaf blades filiform, lax. 



2. 1 ). ELONG \ 1'A. 



2. Glumes shorter than the florets: panicle open, nodding, 10 to 25 cm. long, 



the branches drooping; leaf blades firm, flat or folded. 3. D. CAESPITOSA . 



