126 GRASSES OF SCOTLAND. 



83. Trisetum flavescens. * 

 Yellow Oat- Grass. 



Specific Characters. — Radical leaves and sheaths hairy. Ligule 

 very short and obtuse. (Plate LIV.) 



Description. — It grows from one to two feet high. The root is 

 perennial, somewhat creeping. Stem erect, round, smooth and polish- 

 ed, bearing six or seven leaves with striated sheaths ; the upper sheath 

 about twice the length of its leaf, crowned with a short obtuse ligule ; 

 lower sheaths covered more or less with long, soft, deflexed hairs. 

 Joints four or five, smooth, often furnished with a circle of deflexed 

 hairs underneath. Leaves flat, acute, more or less rough on both 

 surfaces, hairy on the inner surface. Injiorescence panicled. Panicle 

 erect, spreading, rachis and branches very slightly scabrous, the lower 

 branches arising from the rachis mostly in fives. Spikelets small, 

 erect, numerous, usually of three awned florets, projecting beyond 

 the calyx. Calyx of two unequal membranous acute glumes (Fig. 

 1) ; roughish on the keels ; the lower glume the smaller, about one- 

 third shorter than the upper glume without lateral ribs ; the upper 

 glume three-ribbed, and of a light green on the back. Florets of 

 two paleae (Fig. 2) ; the outer palea of lowermost floret membranous, 

 tinged with light green, bifid at the summit, five-ribbed, hairy at the 

 base. Inner palea membranous, linear, acute, shorter than the outer 

 palea, and very minutely fringed. Aicn longer than the palea, slen- 

 der, rough, twisted at the base, becoming bent when dry ; arising 

 from the back of the outer palea a little above the centre. 



Ohs. — Trisetum fiavescens is distinguished from Trisetum pubescens, 

 in the spikelets being much smaller and more numerous, and the li- 

 gule very short and obtuse ; — whereas in T. pubescens the spikelets are 

 more than twice the size and the ligule is long and acute. (Plate 



Lin.) 



This grass grows naturally in almost every kind of soil, from the 

 limestone rock to the irrigated meadow, and is always present in the 

 richest natural pastures. It thrives best in a dry calcareous soil, and 



* Trisetum flavescens, Lindley. Arena flavescens, Koch, Smith, Hooker, Greville. 



