DESCEIPTIONS 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 covipressa 

 so closely that both 

 are employed as 



adulterants, the fig. e.— seeds of rough-stalked meadow grass (Poa tririalis): a and b, 



forniPr iniTirentlv back views; c-e, side views; /and g. front views; g, a terminal floret. 



to considerable extent, since it has frequently been found to constitute 

 a considerable part of samples of so-called rough-stalked meadow 

 grass. One sample examined marked ''^ Poa trivial is''' from Europe 

 consisted almost wholly of Poa compressa. Several samples from 

 Europe contained prickles of Canada thistle, but no seeds of Canada 

 bluegrass were found. 



The principal distinguishing characters of the three species may be 

 compared as follows: 



Rough-stalked meadow geass 

 {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 F. pra- 

 tensis or P. cornpressa. 



Kentucky bluegrass 

 (Poa})ratensis). 



Canada bluegrass 

 {Poa cornpressa). 



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 often 

 strongly distended. 



Seeds straight, the glume 

 margins somewhat evi- 

 dent from the side. 



Apex of the glume often 

 torn, otherwise some- 

 what keeled, obtusely 

 pointed, broader than the 

 base, hyaline-edged. 



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- Intermediate veins indis- 

 tinct as rather coarse tinct or apparently want- 

 ridges, ing. 



Rachilla segment coarser than in I', trivialis and often 

 very short. 



