24 



THE SEEDS OF THE BLUEGRASSES. 



Poa compressa L. 



CANADA BLUEGRASS, FLAT-STEMMED BLUEGRASS. 



Spikelets 3-9 flowered; florets 2-2J mm. long, oblong-obovate or the terminal one 

 lanceolate as viewed from the back, somewhat narrowly oblong as viewed from the 

 side, obtuse or the terminal one acute, smooth between the veins, straw colored or 

 light brown; glume somewhat arched, especially at the base, and strongly keeled at 

 the back, the keel often less pronounced at the apex than at the base; margins 

 infolded from the base for about three-fourths the length of the floret in the lower 

 florets and nearly to the apex in the upper ones, hyaline-edged above the middle, 

 often broadly so at the apex, which is more or less flaring in the lower florets, the 

 thai apex often torn and jagged in commercial seed; intermediate veins very indis- 

 tinct or not evident, glabrous; keel and marginal veins silky pubescent below the mid- 

 dle; basal web present, slight; palea nearly or quite equaling the glume, finely hispid- 

 ciliate on the keels, which are usually more or less exposed above the middle, sometimes 

 from the base; rachilla segment glabrous, varying from about one-fifth the length 



of the glume in the 

 lower florets to one- 

 half its length in the 

 terminal one; aborted 

 floret of the sterile 

 rachilla segment min- 

 ute; grain 1-1 J mm. 

 long, keeled and 

 slightly grooved, 

 semitranslucent. 

 (Fie 



Fig. 5.— Commercial seeds of Canada bluegrass (Poa compressa) : a and b, 

 back views; c-e, side views; /-(', front views of florets; i, a terminal floret. 



o. 



The .seed of Canada l)lueoTass is the cheapest of the l)IuegTass seeds, 

 and is therefore not adulterated with other Poas. although it is itself' 

 used as an adulterant to a considera))le extent. 



Pure samples of Canada bluegrass seed almost always contain the 

 prickles and sometimes the seeds of Canada thistle {Carduus arvensis); 

 therefore, the occurrence of these prickles with other kinds indicates 

 the use of this species as an adulterant. Their occurrence with seed 

 of Poa trwicdh without evidence of the presence of Canada bluegrass 

 seed is noted under the discussion of 1\ trivialis. 



Poa trivialis L. 



ROUGH-STALKED MEADOW GRASS. 



Spikelets 2 or 3 flowered; florets 2-2J mm., rarely 3 mm., long, narrowly lanceolate 

 or the fertile terminal one ovate-lanceolate as viewed from the back, usually lanceolate 

 and curved as viewed from the side, laterally compressed as compared with other spe- 

 cies, straw colored or light brown and sometimes purplish, sharply keeled, the keel 

 somewhat arched; margins of the glume scarcely or but slightly distended, narrowly 

 and rather sharply infolded nearly or quite to the apex, which is hyaline-edged, very 

 acute and rarely expanded; intermediate veins very di.'^tinct as narrow and sharply 

 defined ridges; keel slightly pubescent below the middle, or rarely smooth; marginal 

 veins smooth or sometimes pubescent, basal Aveb present; palea nearly equal to the 

 glume, its keels smooth or finely hispid-cdiate near the apex and mostly covered by 

 the margms of the glume except in the larger termmal florets; rachilla segment very 

 slender, glabrous, varying from one-fourth to one-halt the length of the glume; 

 gram 1-1^ mm. long, keeled and grooved, semitranslucent, reddish brown. (Fig. 6.) 



