366 



GRASSES 



GRASSES 



of the grasses. In some cases reference is made to 

 special articles on the individual grasses for the 

 cultural notes. For cultural notes on all others the 

 reader should consult Spillman's article on Meadows 

 and Pastures. 



KEY TO GENERA 



A. Spikelets dorsally compressed, with one perfect 

 flower, sometimes a staminate flower below the perfect 

 one, falling from the pedicels entire, either singly, in 

 groups or together with joints of an articulate rachis : 



Flowers unisexual ; staminate spike- 

 lets in a terminal panicle, pistil- 

 late spikelets in axillary fascicled 

 spikes more or less enveloped in 

 large bracts (husks): 

 Pistillate spikes compound; grains 

 in several to many rows about a 



thickened axis (cob) 1. Zea 



Pistillate spikes simple, breaking 

 into joints at maturity .... 2. Euchlsena 

 Flowers perfect, or staminate and pis- 

 tillate together in same inflores- 

 cence : 

 Glumes hardened ; lemma and palea 

 very thin : 



Spikelets all perfect, enveloped in 

 long hairs, forming a dense silky 



panicle 3. Saccharum 



Spikelets of two kinds, — the per- 

 fect sessile, with a staminate 

 one pedicellate on either side . 4. Sorghum 

 Glumes thin, lemma and palea 

 hardened ; spikelets all perfect : 

 Spikelets not sunken in notches of 

 the axis : 

 Involucre none : 

 Inflorescence spioate : 

 Spikes digitate ; spikelets lan- 

 ceolate 5. Syntherisma 



Spikes racemose ; spikelets 



nearly circular 6. Paspalum 



Inflorescence paniculate : . . . 7. Panicum 

 Involucre of bristles below the 

 spikelet : 

 Grain enclosed in lemma and 



palea at maturity 8. Chstochloa 



Grain globose, forcing open 



lemma and palea at maturity 9. Pennisetum 

 Spikelets sunken in notches of the 

 flattened corky axis 10. Stenotaphrum 



AA. Spikelets laterally compressed, one to many-flow- 

 ered, the rachilla usually articulated above the glumes 

 which remain on the pedicel after the florets have fallen ; 

 (glumes deciduous in Oryza, Alopecurus and Holcus). 



Spikelets not disposed in alternate 

 notches on opposite sides of a flat- 

 tened rachis : 

 Stamens 6 ; glumes minute . , , . 11. Oryza 

 Stamens 3 ; glumes more than half 

 as long as florets: 

 Perfect floret 1 in each spikelet : 

 Fertile floret awnleas, with 2 

 sterile lemmas below, falling 

 attached to it: 

 Sterile lemmas minute, awnless 12. Phalaris 

 Sterile lemmas larger than the 



fertile one, awned 13. Anthoxanthum 



Fertile floret awnless ; a stami- 

 nate, awned one below, not 

 falling attached .14. Arrhenatherum 



Fertile floret awned or awnless, 

 no sterile floret below : 

 Inflorescence a dense cylindri- 

 cal spike-like panicle : 

 Spikelets small ; glumes longer 

 than the very thin lemmas : 

 Glumes abruptly aristate ; 



lemma awnless 15. Phleum 



Glumes not aristate ; lemma 

 awned on the back ... 16. Alopecurus 

 Spikelets about 1 cm. long; 

 glumes and lemma chartace- 



ous, sub-equal 17. Ammophila 



Inflorescence an open panicle . 18. Agrostis 

 Inflorescence of slender spikes, 

 digitate at summit of culms . 19. Cynodon 

 Perfect florets two to many in each 

 spikelet : 

 Plant velvety ; spikelets falling 



from the pedicel entire . . .20. Holcus 

 Plant not velvety ; glumes per- 

 sistent on the pedicel : 

 Florets exceeded by the papery, 



striate glumes 21. Avena 



Florets not exceeded by the 

 glumes : 



Spikelets flattened, in dense, 

 one-sided clusters at the 

 ends of the few panicle 



branches 22. Dactylis 



Spikelets not in one-sided 



clusters : 



Inflorescence a dense spike ; 



spikelets of two forms, the 



fertile surrounded by sterile 



ones 23. Cynosurus 



Inflorescence an open or nar- 

 row panicle; spikelets all 

 alike : 

 Lemma keeled ; awnless, 



often cobwebby at base . 24. Poa 

 Lemma convex ; never cob- 

 webby : 

 Apex of lemma entire ; 



acute or awned .... 25. Festuca 

 Apex of lemma two- 

 toothed, awned just be- . 

 low the apex or awnless ; 

 grain adherent to the 



palea 26. Bromus 



Spikelets sessile in alternate notches 

 on opposite sides of a flattened 

 rachis, forming slender or dense 

 spikes : 

 Joints of the rachis with one spike- 

 let each : 

 Placed edgewise on the rachis ; 



glume 1 27. Lolium 



Placed with one side against the 

 rachis ; glumes 2 : 



Glumes bristle-like, one-nerved . 28. Secale 

 Glumes lanceolate to ovate ; sev- 

 eral-nerved : 

 Rachilla not articulated ; florets 



persistent ; lemma ovate . . 29. Triticum 

 Rachilla articulated above the 

 glumes and between the flo- 

 rets, which fall separately ; 



lemma lanceolate 30. Agropyron 



Joints of the articulate rachis with 

 2 or 3 spikelets each; glumes 

 bristle-like 31. Hordeum 



