DESCRIPTIONS OF SPECIES. 25 
Rough-stalked meadow grass is chiefly hand gathered; consequently 
the commercial seed is apt to bear more or less of the web as well as 
the silky pubescence on the keel. In many samples, however, both 
are rubbed away. 
This seed resem- 
bles that of Poa 
pratensis and that 
of Poa compressa 
so closely that both 
are employed as 
adulterants, 
former apparently 
to considerable extent, since it has frequently been found to constitute 
a considerable part of samples of so-called rough-stalked meadow 
ee 
*s 
+i 
th € Fic. 6.—Seeds of rough-stalked meadow grass (Poa trivialis): a and b, 
back views; c-e, side views; f and g, front views; g, a terminal floret. 
gYass. 
consisted almost wholly of Poa compressa. 
Europe contained prickles of Canada thistle, but no seeds of Canada 
bluegrass were found. 
One sample examined marked ‘* Poa trivialis” from Europe 
Several samples from 
The principal distinguishing characters of the three species may be 
compared as follows: 
ROUGH-STALKED MEADOW GRASS 
(Poa trivialis). 
Commercial seeds are usu- 
ally pubescent on the 
keel vein, usually smooth 
on the marginal veins 
and bear more or less of 
the webby hairs, conse- 
quently cling together in 
masses. 
As viewed from the side, 
the seeds are somewhat 
curved, much narrower 
than the others, the 
glume margins usually 
only slightly evident. 
Apex of the glume usually 
uninjured, strongly 
keeled, acute, slightly 
hyaline-margined, often 
curved. 
Intermediate veins sharply 
defined as narrow ridges. 
Rachilla segment very slen- 
der and less variable in 
length than in P. pra- 
tensis or P. compressa. 
KENTUCKY BLUEGRASS 
(Poa pratensis). 
CANADA BLUEGRASS 
(Poa compressa). 
Commercial seeds rarely pubescent on the veins and 
the webby hairs wanting; consequently mobile in bulk, 
not clinging in masses; unrubbed seed pubescent on 
the marginal and keel veins. 
Seeds mostly straight as 
viewed from the side, 
glume margins citen 
strongly distended. 
Apex of the glume more or 
less torn in commercial 
seed; keeled, sharply 
pointed, hyaline-edged 
and not curved in un- 
rubbed seed. 
Intermediate veins dis- 
tinct as rather coarse 
ridges. 
Seeds straight, the glume 
margins somewhat eyi- 
dent from the side. 
Apex of the glume often 
torn, otherwise some- 
what keeled, obtuselty 
pointed, broader than the 
base, hyaline-edged. 
Intermediate veins indis- 
tinct or apparently want- 
ing. 
Rachilla segment coarser than in P. trivialis and often 
very short. 
