270 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



9. AVENEAE. 



Articulation below the spikelet. 



Second glume narrowed above ; lemma of second floret awned on the back, 



the awn hooked 70. Notholcus (p. 371). 



Second glume broadened above ; lemmas awnless. 



72. Sphenopholis (p. 372). 

 Articulation above the glumes and between the florets. 



Spikelets awnless 73. Koeleria (p. 372), 



Spikelets awned. 



Awn from between the teeth of the lemma, flat, twisted below. 



75. Danthonia (p. 372). 

 Awn dorsal, terete, straight or twisted. 



Spikelets less than 1 cm. long, erect ; panicle dense, spikelike. 



71. Trisetum (p. 371). 

 Spikelets more than 1 cm. long, drooping 74. Avena (p. 372). 



10. CHLORIDEAE. 



Plants monoecious or dicecious ; pistillate spikelets many-awned ; staminate 



spikelets awnless; plant stoloniferous 87. Opizia (p. 384). 



Plants with perfect spikelets. 



Spike solitary, terminating the culm. 



Spikelets with 1 perfect long-awned floret 80. Saug'etia (p. 378). 



Spikelets with several perfect short-awned florets. 



82. Tripog-on (p. 381). 

 Spikes 2 or more on each culm. 



Spikes racemosely arranged. 



Spikelets articulate below the glumes, 1-flowered ; maritime grasses 



with stout rhizomes 77. Spartina (p. 373), 



Spikelets articulate above the glumes, 2 to several-flowered (the 

 second floret rudimentary in Bouteloua). 

 Spikes short and relatively broad ; upper floret often reduced 



to the awns 81. Bouteloua (p. 379). 



Spikes long and slender ; perfect florets 2 or more. 



Lemmas awnless or with minute awns, the upper floret 

 reduced to an awnless small lemma. 



85. Leptochloa (p. 382). 

 Lemmas with awns as long as the body, the upper floret 



reduced to a slender awn 86. Gouinia (p. 384). 



Spikes digitate or nearly so. 



Spikelets with 2 or more perfect florets. 

 Rachis extending beyond the spikelets. 



84. Dactyloctenium (p. 382). 

 Rachis not extending beyond the spikelets. 



83. Eleusine (p. 381). 

 Spikelets with 1 perfect floret only. 



Sterile floret wanting; lemma obtuse 76. Capriola (p. 373). 



Sterile floret present ; lemma awned or mucronate. 



Fertile floret raised on a long stipe ; sterile florets reduced 



to long awns 79. Gymnopogon (p. 377). 



Fertile floret not raised on a stipe; sterile florets consist- 

 ing of evident lemmas 78. Chloris (p. 374), 



