COMPARATIVE ANALYSIS. 



237 



CYNOSTJRUS. Outer palea terminating in a short awn, not half 



length of palea .... Cristatus. 

 Outer palea terminating in a long awn as long as 



the palea . . . EcUnatus. 



POA. Florets webbed ... 1 



Florets not webbed ... 4 



1. Upper leaf much longer than sheath ... 2 

 Upper leaf about as long or longer than sheath . . 3 



2. Ligule of upper sheath short and rounded . . Pratensis. 

 Ligule of upper sheath long and pointed . . Trivialis. 



3. Ligule scarcely perceptible, outer palea five-ribbed . Nemoralis. 

 Ligule prominent, outer palea three-ribbed . . Compressa. 



4. Florets hairy at base .... 5 

 Florets not hairy . . . . .12 



5. Outer palea three-ribbed .... 6' 

 Outer palea five-ribbed . . . . .7 



6. Panicle erect, upper leaf linear, folded . . . Alpina. 

 Panicle drooping, upper leaf lanceolate, flat . . . Laxa. 



7. Upper joint situated above centre of stem . . 8 

 Upper joint situated below centre of stem . . < .9 



8. Second sheath not reaching to first joint . . Polynoda. 

 Second sheath extending beyond first joint . . Montana. 



9 Small glume reaching beyond base of third floret . 10 



Small glume not reaching beyond base of second floret . 11 



10. Rachis and branches rough .... Ccesia. 

 Rachis and branches smooth .... Annua. 



11. Eachis and branches rough to touch .. . Distans. 

 Rachis and branches smooth to touch . f '. Maritima. 



12. Glumes with a prominent lateral rib on each side . Procvmbens. 

 Glumes without lateral ribs . . . : . 13 



13. Lower half of central rib of outer palea smooth . . 14 

 Central rib of outer palea rough the whole length . .15 



14. Summit of upper glume reaching to base of third floret . Rigida. 

 Summit of upper glume reaching to base of fourth floret . Loliacea. 



15. Outer palea three-ribbed .... Sylvatica. 

 Outer palea seven-ribbed . . . .16 



16. Panicle compound, spikelets not a quarter of an inch in 



length ..... Aquatica. 



Panicle simple, spikelets an inch in length . . Fluitans. 



BTTCETUM. Inflorescence racemed, approaching to a spike . Loliaceum. 



Inflorescence panicled . . . . 1 



1. Panicle simple ..... Pratense. 

 Panicle compound . . . . .2 



2. Awn considerably shorter than palea . . . Elatius. 

 Awn considerably longer than palea . . Giganteum. 



