20-i GRASSES OF BRITAIN. 



POA SUBCOMPRESSA. 



Flat-stalked Five-ribbed 3Ieadoiv- Grass. 

 Plate XC. 



Specific Characters. — Florets webbed. Outer palea five-ribbed. 

 Marginal ribs hairy. Stem very much compressed. Ligule obtuse. 



Description. — Root perennial, creeping, producing stems fi-om six 

 to fifteen inches in length. Stems erect, decumbent at the base, 

 smooth, hollow, very much compressed, bearing four or five leaves 

 with smooth, striated, compressed sheaths ; upper sheath about equal 

 in length to its leaf. Ligide of upper sheath short and obtuse, about 

 twice as long as broad. Joints four or five, the upper generally situ- 

 ated about the middle of the stem. Leaves rather short, flat, acute, 

 rough on the upper surface and edges, smooth behind. Inflorescence 

 simple panicled, spreading while in flower, otherwise close, the 

 branches and rachis rough ; lower part of the rachis much smaller than 

 the stem. Spikeleis ovate, acute, compressed, composed of two glumes 

 and from five to seven florets, the summit of the lowermost floret 

 extending slightly beyond the large glume. Glumes rather unequal, 

 three-ribbed, minutely toothed on the upper part of the keels. Florets 

 of two palese, the outer palea of the lowermost floret five-ribbed; the 

 lower half of the dorsal and marginal ribs hairy; the base, furnished 

 with a delicate web, attached to the glumes. Inner palea rather 

 shorter than the outer, with two green ribs minutely fringed. Styles 

 two, distinct. Stigmas feathery. Filaments three, capillary. Anthers 

 notched at each end. Scales acute, notched. 



Obs. — Poa svbcompressa very much resembles Poa compressa, but 

 is readily distinguished in the outer palea having five distinct ribs in- 

 stead of only three. When under cultivation the panicle does not 

 grow to half the size of that of Poa compressa. 



Poa subcompressa is distinguished from Poa polynoda in \h& florets 

 being distinctly webbed, and the ligules shorter and more obtuse ; — 

 while in Poa polynoda the florets are never webbed. 



Poa subcompressa is distinguished irom Poa pratensis in the sheaths 



being very much compressed, nearly flat ; upper leaf about equal 

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