(304) 



Ovary sessile, hirsute at the apex; caryopsis 

 terete, adherent to the upper palet. — 0. 



1. A. FATUA L. — Common. Summer. 

 17. Trisetum Kimth. 



Spikelets 2-4-flpAvered. the uppermost depau- 

 perate. Ghimes 2, carinate, awnless, shorter 

 than the flower. Palets 2; lower 2-dentate, 

 aristate. Ovary sessile; caryopsis compressed, 

 free. Leaves flattened. 



1. T. CANESCENS Buckl. Spikelets 2 or 3- 

 flowered, narrow; lower glume narrow, con- 

 siderably shorter than the bro.id ovate upper 

 one. — 0. Common. Spring. 



2. T. BARBATUM Steud. Spikelets 3-5-flow- 

 ered, lari;e, much flattened; both glumes nar- 

 row, the lower but little shorter than the up- 

 per one. — 0. Common. Spring. 



18. Aira L. Hair-Grass. 



Spikelets 2-flowered, often with the rudiment 

 of a superior one. Flowers sessile. Glumes 2, 

 carinate, awnless, larger than the flower. Palets 

 2; the lower 2-cleft, dorsally aristate. Ovary 

 sessile; caryopsis free. 



1. A. c^spitosaL. Glumes not longer than 

 the florets; spikelets much compressed. — 21. 

 San Francisco. Summer. 



2. A. HOLCiFORMis Steud. Glumes not longer 

 than the florets; spikelets nearly terete. — IC. 

 Common. Summer. 



