140 



CLASSIFICATION OF 



[CH. 



The "seeds" of Poa proper are nearly all small — not more than 

 3 — 4 mm., more or less lanceolate, with tough, keeled glumes, and 

 when "webbed" tend to adhere together as if stuck with cobweb. 

 The keeled glumes give them an angular appearance — triangular 

 in section — and make them tend to lie on the side. RachiUa 

 evident. Nerves of paleae distinct. 



Poa pratensis, L. (Fig. 55). 



" Seed " 2 — 3 mm. long, brownish : caryopsis about 

 1 — 1"5 mm. Outer palea acute, indistinctly 3 — 5 nerved, 

 edges and keel, silky ; margins overlapping the hyaline 

 inner palea. 



The " web " looks like hyphse of a mould. 



Caryopsis ellipsoid-acute, with traces of the stigma. 

 It falls easily. No distinct groove, section somewhat 

 triangular. Rachilla truncate. 



Fig. 54. Poa nemoralis. 

 c, the mitiute "seed" 

 (to the right) and 

 caryopsis (to the left) 

 nat. size. a, the 

 "seed," x8; 6, the 

 caryopsis, x 8. Traces 

 of a basal " web," not 

 shown here, ooeasion- 

 ally occur. Nobbe. 



Fig. 55. Poa pratensis. 

 Type of a " webbed 

 seed." u, " seed," 

 X about 7; 6, cary- 

 opsis (inverted), x7. 

 Between are the same, 

 nat. size. Note the 

 nerves on the palea 

 and the conspicuous 

 " web " at the base a. 

 Nobbe. 



Fig. 56. Poa trivialis. 

 a, "seed," nat. size 

 and X 8 ; 6, cary- 

 opsis, nat. size and 

 X 7. Note the con- 

 spionous " web." 

 Nobbe. Cf . Fig. 43. 



Poa compressa, L. 



Palea obtuse, nearly glabrous and nerveless, or faintly 



