GENERA OF GRASSES OF THE UNITED STATES. 
17 
Key to the genera of Chlorideae — Continued. 
7a. Spikelets without additional modified florets, the rachilla sometimes 
prolonged 8 
8a. Rachilla articulate below the glumes, the spikelets falling entire- 9 
9a. Glumes unequal, narrow 90. Spartina. 
9b. Glumes equal, broad and boat shaped 89. Beckmannia. 
8b. Rachilla articulate above the glumes 10 
10a. Spikes digitate; rachilla prolonged , 86. Capriola. 
10b. Spikes racemose along the main axis ; rachilla not prolonged- 11 
11a. Spikes slender, divaricate, the main axis elongating and 
becoming loosely spiral in fruit 88. Schedonnaedus. 
lib. Spikes short and rather stout, appressed, the axis un- 
changed in fruit 87. Wiixkommia. 
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. Camptjlostjs. 
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. Chlokis. 
14b. Fertile lemma 3-awned 94. Trichloeis. 
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. 
lb. Lateral florets neuter ; spikelets green or yellowish 2 
2a. Lateral florets reduced to small awnless scalelike lemmas ; spike- 
lets much compressed laterally 101. Phaiaris. 
2b. Lateral florets consisting of awned hairy sterile lemmas exceed- 
ing the fertile floret ; spikelet terete 100. Anthoxantetum. 
97769°— 19— Bull. 772^ 2 
