82 Bulletin VII. 1. 



dense, or loose panicles; rachilla hairy or naked, articulated above 

 the empty glumes and between the florets, prolonged beyond the 

 base of the upper floret as a (usually) hairy bristle. Empty glumes 

 two, awnless, carinate, unequal, usually longer than the floral 

 glumes; floral glumes sub-hyaline, carinate, cleft, or two-toothed at 

 the apex, the teeth sometimes produced into slender awns, awned 

 between or a little below the teeth. Awn twisted and usually 

 geniculate. Palea narrow, two-tooched. Grain smooth, enclosed 

 in the floral glume and palea, but free from them. Cespitose 

 perennials (rarely annuals), with flat leaves and dense spike-like, 

 or narrow, loose panicles. 



Species fifty, from the arctic regions through the temperate zone 

 and along the high mountains of the tropics, to the south tem- 

 perate countries. North American species, nine. There are two 

 native species in Tennessee. 



1. Trisetum subspicatum var. molle Gray. 



Plate XXVII. Figure 108. 



A slender, erect perennial six to fifteen inches high, with soft, 

 downy culms, sheaths and leaves, and a contracted spike-like pani- 

 cle two to five inches long. Spikelets about three lines long, two- 

 to three-flowered; empty glumes about the length of the florets. 

 Awn of the floral glumes exserted, divergent. 



Summit of Roane mountain. July. Of no known value in 

 agriculture. 



2. Trisetum palustre Torr. 



Plate XXVIII. Figure 109. 



A smooth, upright perennial one to two and one-half feet high, 

 w^ith rather short flat leaves and a loosely- flowered, narrow, yel- 

 lowish-green panicle. Sheaths loose, smooth, shorter than the in- 

 ternodes; ligule short, lanceolate; leaf-blade about three inches 

 long, with minutely serrulate margins. Panicle about five inches 

 long, its branches capillary. Spikelets compressed, two-flowered, 

 about three lines long; empty glumes nearly equal, keeled, shorter 

 than the florets; flowering glumes lanceolate, the first awnless or 

 short-awned from the tip; the second with a slender, spreading or 

 geniculate awn from just below the sharply two-toothed apex. 

 Paleas about one-third shorter than their glumes. 



In moist situations. Mountains of East Tennessee. July. 



Yellow Oat-grass ( Trisetum flivescens) is a recently introduced 

 species which has some recognized agricultural value. It forms 

 loose tufts eighteen inches to two feet high, and grows well on al- 

 most all soils. It is especially valuable in mixtures designed for 

 the formation of permanent pastures. 



31. AVENA Linn. Sp. PI. 79. (1753.) 



Spikelets two- to six-flowered, in loose or dense panicles: rachilla 

 articulated above the empty glumes, hairy under the flowering 



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