﻿GRASSES OF SCOTLAND, 97 



64. POA RIGIDA. * 



Hard Meadow- Grass. 



Specific Characters. — Florets not webbed. Summit of the upper 

 glume on a level with the base of the third floret. Glumes without 

 lateral ribs. (Plate XLIII.) 



Description. — It grows from three to five inches high. The root 

 is annual, fibrous, woolly. Stem mostly erect, the low T er part decum- 

 bent, smooth, round, and finely striated, bearing four or five leaves 

 with smooth striated sheaths ; the upper sheath shorter than its leaf, 

 crowned with a long pointed ligule. Joints three or four, smooth. 

 Leaves linear, narrow, taper-pointed, involute, roughish on the upper 

 part, smooth below. Inflorescence simple panicled. Panicle erect, 

 rigid, of a lanceolate form, with very short, roughish, rigid, unilate- 

 ral branches, leaving the rachis behind perfectly bare. Spikelets li- 

 near, compressed, usually of seven florets (Fig. 3), the summit of the 

 lower floret extending but slightly beyond the large glume of the ca- 

 lyx. Calyx of two acute unequal glumes (Fig. 1 ), without lateral ribs. 

 Florets of two palese (Fig. 2) ; the outer palea of lowermost floret 

 Jive-ribbed ; the marginal ribs broad, with a white line down the cen- 

 tre ; the intermediate ribs scarcely perceptible ; the dorsal rib tooth- 

 ed on the upper part, and protruding slightly beyond the summit of the 

 palea (Fig, 4). Inner palea rather shorter than the outer, with two 

 green marginal ribs but slightly fringed on the upper part. 



Q os% — poa rigida, on account of its small size and rigid appear- 

 ance, can only be mistaken for Poa loliacea, and on some occasions 

 these two species so very much resemble each other, that they can 

 scarcely be distinguished by any constant character. The only cha- 

 racter that I have been able to discover by which they can at all times 

 be distinguished from one another is derived from the spikelet, that 

 is, in Poa rigida the summit of the upper glume is on a level with the 

 base of the third floret ; — whereas in Poa loliacea it is on a level with 

 the base of the fourth floret. This character, however trivial it may 

 appear, will be found constant. 



* Poa rigida, Linn., Hooker, Greville. Glyceric rigida, Smith, ^ckrochloa rigida,, 

 Link., Lindky. Festuca rigida, Kunth., Koch. 



