24 THE SEEDS OF THE BLUEGRASSES. 
Poa compressa L. 
CANADA BLUEGRASS, FLAT-STEMMED BLUEGRASS. 
Spikelets 3-9 flowered; florets 2-23 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 ior 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 
thin 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 orless exposed above the middle, sometimes 
from the base; rachilla segment glabrous, varying from about one-fiith 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 1-13 mm. 
long, keeled and 
slightly grooved, 
semitranslucent. 
(Fig. 5.) 
Fie. 5.—Commercial seeds of Canada bluegrass (Poa compressa): a and B, 
back views: c-e, side views: j-i, front views of florets; 7,a terminal fioret. 
The seed of Canada bluegrass is the cheapest of the bluegrass seeds, 
and is therefore not adulterated with other Poas, although it is itself 
used as an adulterant to a considerable 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 speciesas an adulterant. Their occurrence with seed 
of Poa trivialis without evidence of the presence of Canada bluegrass 
seed is noted under the discussion of P. tr/valis. 
Poa trivialis L. 
ROUGH-STALKED MEADOW GRASS. 
Spikelets 2 or 3 flowered; florets 2-23 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 distinct as narrow and sharply 
defined ridges; keel slightly pubescent below the middle, orrarely smooth; marginal 
veins smooth or sometimes pubescent, basal web present; palea nearly equal to the 
glume, its keelssmooth or finely hispid-ciliate near the apex and mostly covered by 
the margins of the glume exceptin the larger terminal florets; rachilla segment very 
slender, glabrous, varying from one-fourth to one-half the length of the glume; 
grain 1-1} mm. long, keeled and grooved, semitranslucent, reddish brown. (Fig. 6.) 
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Sreptld 
