MANUAL OF THE GRASSES OF THE UNITED STATES 337 



Panicle dense and spikelike; lemma minutely 4-toothed; palea % to 3^ as long 



as the lemma . 26. A. californica. 



5b. Panicle open, sometimes diffuse; branches very slender, scabrous, the lower 

 branches not spikelet-bearing at the base. 

 Lemma awned from near the base. 



Blades elongate, 3 to 5 mm. wide; panicle branches flexuous; spikelets about 



3.5 mm. long 28. A. how t ellii. 



Blades about 1 mm. wide or less; panicle branches straight; spikelets 2 to 2.5 mm. 



long 27. A. hooveri. 



Lemma awnless or awned from the middle or above. 



Panicle very diffuse, the capillary branches branching toward the end or (in 

 A. scabra var. geminata) above the middle. 

 Spikelets 1.5 to 1.7 mm. long, very densely clustered at the ends of the branch- 

 lets; lemma 1 to 1.2 mm. long, scarcely longer than the caryopsis; anthers 



about 0.2 mm. long 29. A. hiemalis. 



Spikelets 2 to 2.7 mm. long, loosely arranged at the ends of the branchlets; 

 lemma 1.5 to 1.7 mm. long, distinctly longer than the caryopsis; anthers 



0.4 to 0.5 mm. long 30. A. scabra. 



Panicle open but not diffuse, the branches branching at or below the middle. 

 Lemma awnless (occasional plants with awned lemmas). 



Spikelets about 2 mm. long; plants of high altitudes, delicate, 10 to 30 cm. 



tall 31. A. IDAHOENSIS. 



Spikelets 2 to 3 mm. long; more robust plants of low and medium altitudes. 

 Panicle rather lax, sometimes delicate and divaricately spreading; blades 

 flat, as much as 6 mm. wide; eastern United States. 

 Spikelets mostly 2.2 to 2.7 mm. long, not aggregate or but slightly so 



at the ends of the panicle branches 32. A. perennans. 



Spikelets mostly 2.7 to 3.5 mm. long, aggregate towards the ends of 



the panicle branches 33. A. altissima. 



Panicle rather stiff, the branches whorled and rather stiffly ascending; 



Pacific coast 34. A. oregonensis. 



Lemma awned. 



Spikelets about 2 mm. long; introduced 35. A. canina. 



Spikelets 2.5 to 3 mm. long; native. 



Ligule 1 to 2 mm. long 36. A. borealis. 



Ligule 5 to 8 mm. long 37. A. longiligula. 



Figure 460. — Agrostis 

 avenacea. Panicle, X 

 H; glumes and floret, 

 X 10. (Tracy and 

 Earle 403, Tex.) 



1. Agrostis avenacea Gmel. (Fig. 

 460.) Perennial; culms tufted, erect or 

 decumbent at base, 20 to 60 cm. tall; 

 sheaths smooth; ligule of culm leaves 

 3 to 5 mm. long; blades flat, scabrous, 

 1 to 2 mm. wide; panicle diffuse, 15 to 

 30 cm. long, the branches in distant 

 whorls, capillary, reflexed at maturi- 



ty, divided above the middle; glumes 

 acuminate, 3 to 4 mm. long; lemma 

 about half as long as the glumes, thin, 

 pubescent, short-bearded on the cal- 

 lus, and bearing about the middle a 

 slender geniculate and twisted awn 

 exserted about the length of the 

 glumes; palea nearly as long as the 



