526 POACE.E. 



126. (256). POA L. Sp. PL 67 (1753). Poidium Nees, Lindl. 

 Introd. Nat. Syst. Ed. 2, 450 (1836). AUagostachyum Nees, 

 Steud. Norn. Ed. 2, 1 : 50 (1840). Plotia Schreb. Steud. Norn. 

 Ea. 2, 2:356 (1841). 



Spikelets of medium size, compressed-keeled, 2-6- (rarely 

 7-10-) flowered, pedicellate in a pauicle usually loose and spread- 

 ing, rarely narrow and spikelike, rachilla articulate between the 

 floral glumes, glabrous or rarely pilulose, flowers perfect or 

 some of the upper ones imperfect. Empty glumes membran- 

 ous, keeled, acute or obtuse, unawned, persistent, 1-3-nerved, 

 commonly shorter than the floral glumes; floral glume mem- 

 branous or herbaceous with a delicate scarious margin, usually 

 obtuse and surrounded by a few loose woolly hairs, 5, rarely 

 7, nerved, the nerves usually bending toward each other near the 

 apex; palea nearly as long as its glume, prominently 2-nerved or 

 2-ke9led. Stamens 2-3. Styles short, or very short, distinct, stig- 

 mas plumose. Grain ovcid, oblong, or almost linear, compressed, 

 and rarely wath a brc2.d groove, glabrous, included by glume and 

 palea, free or adhering more or less to the palea when mature. 



There are about 80 species, though some authors have extended 

 the number to 200. The genus is the most widely diffused over the 

 globe of any in the family, chiefly in temperate and cool regions, 

 reaching the Arctic circle and Alpine summits; very few in the 

 tropics. The genus is a very natural one, well distinguished from 

 Eragrostis, Panicularia {Glyceria), and Festuca by the nerves usu- 

 iilly connivant in the apex of the floral glumes. By many authors 

 Poa is made to include Afropis. 



The species differ from Eragrostis in their 5-nerved floral 

 glumes, from Panicularia and Festuca in their glumes keeled from 

 the base; but there are species apparently intermediate between 

 these large genera. Poa has also been distinguished from Festuca 

 by the obtuse, always unawned glumes, and the non-adherence of 

 the grain to the palea. Several species of Poa, however, have acute 

 glumes, and in one species they bear fine points. There are some 

 Chilian and Australian species and some Asiatic ones where the 

 grain is adherent to the palea, as in Festuca; even in Poa pratensis 



