GENEKA OF GRASSES OF THE UNITED STATES. 17 



Key to the genera of Chlorideac Continued. 



7a. Spikelets without additional modified florets, the rachilla sometimes 



prolonged 8 



Sa. Rachilla articulate below the glumes, the spikelets falling entire- 9 



9a. Glumes unequal, narrow 90. SPAETINA. 



9b. Glumes equal, broad and boat shaped 89. BECKMANNIA. 



8b. Rachilla articulate above the glumes 10 



lOa. Spikes digitate; rachilla prolonged 86. CAPRIOLA. 



lOb. Spikes racemose along the main axis ; rachilla not prolonged. 11 

 Ha. Spikes slender, divaricate, the main axis elongating and 



becoming loosely spiral in fruit 88. SCHEDONNARDUS. 



lib. Spikes short and rather stout, appressed, the axis un- 

 changed in fruit 87. WUXKOMMIA. 



7b. Spikelets with 1 or more modified florets above the perfect one_ 12 



12a. Spikelets with 2 sterile florets below the perfect one; second 

 glume bearing a squarrose spine on the back; spike single, 



recurved 91. CAMPULOSUS. 



12b. Spikelets with no sterile florets below the perfect one; second 



glume without a squarrose spine ; spikes usually several 13 



13a. Spikes digitate or nearly so 14 



14a. Fertile lemma 1-awned or awnless 93. CHLOBIS. 



14b. Fertile lemma 3-awned 94. TKICHLOEIS. 



13b. Spikes racemose along the main axis 15 



15a. Spikelets distant, appressed ; spikes slender, elongate. 



92. GYMNOPOGON. 

 15b. Spikelets contiguous or crowded, not appressed ; spikes 



usually short and rather stout -. 16 



16a. Spikelets 3 in each spike, the 2 lateral staminate or 



rudimentary ; spikes falling entire 96. CATHESTECUM. 



16b. Spikelets 2 to many (rarely 1) in each spike, all 

 alike ; spikes usually persistent, the florets falling. 



95. BOUTELOUA. 



TRIBE 8, PHALARIDEAE. 



Spikelets with one perfect terminal floret and, below this, a pair of 

 staminate or neuter florets. 



A small tribe of about six genera, only three of which are found 

 in the United States. In Phalaris the lateral florets are reduced to 

 minute scalelike lemmas closely appressed to the edges of the fertile 

 floret. In Torresia the lateral florets are staminate and as large as 

 the fertile floret. 



Key to the genera of Phalarideae. 



la. Lateral florets staminate ; spikelets brown and shining 99. TORRESIA. 



Ib. Lateral florets neuter ; spikelets green or yellowish 2 



2a. Lateral florets reduced to small awnless scalelike lemmas ; spike- 

 lets much compressed laterally - 101. PHALARIS. 



2b. Lateral florets consisting of awned hairy sterile lemmas exceed- 

 ing the fertile floret ; spikelet terete 100. ANTHOXANTHTJM, 



97769 19 Bull. 772 2 



