48 



GRAMINEJE. 



Introduced from Europe into California about 1876, by Mr. Louis 

 McLane, at tbe instigation of Prof. Geo. Davidson, for binding the 

 drifting coast-sands of Golden Gate Park. Now thoroughly estab- 

 lished at Golden Gate Park, Point Lobos and South Beach, as well 

 as at Point Reyes and Point Arena. July. 



Tribe 5. Aveneae. Oats Tribe. 



Inflorescence in lax, rarely contracted panicles, or in Danthonia 

 sometimes reduced to a raceme of 1 to 10 terminal spikelets. Spike- 

 lets all alike, usually with 2 or more perfect flowers (1 perfect and 1 

 staminate in Holcus and Arrhenatherum; rarely 1-flowered by abor- 

 tion in Deschampsia and Trisetum), the imperfect flowers when 

 present, uppermost (except in Arrhenatherum). Bracts large in 

 proportion to the whole spikelet, usually exceeding the uppermost 

 bractlet. Rachilla, except in Holcus, jointed above the bracts so that 

 these persist after the flower has fallen, prolonged beyond the insertion 

 of the uppermost flower except in Aira. Bractlet usually awned on 

 the back, rarely from between the teeth of the 2-fid apex; awn usually 

 geniculate or twisted. 



A. Bracts readily deciduous with the flower. 



Spikelet strictly 2-flowered; lower flower perfect, its bractlet awnless; upper 

 flower staminate (or rarely perfect), its bractlet with a short awn 



16. Holcus. 



B. Bracts persistent after the flower has fallen. 



Rachilla not prolonged beyond the insertion of the upper flower; spikelets 

 strictly 2-flowered. 



Bractlets hyaline, 2-toothed, dorsally awned; flowers closely superposed. . . 



17. Aira. 



Rachilla prolonged beyond the insertion of the upper flower; spikelets (in ours) 

 2 (rarely by abortion only 1 in De>champsia and Trisetum) to many-flowered. 

 Awn of the bractlet arising from below the teeth of the apexj not from 

 between them. 



Lower flower always perfect; the uppermost sometimes staminate or 

 reduced to its bractlet. 

 Spikelets less than 5 lines long (excluding the awn); achene free from 

 the bractlet and palea, unfurrowed. 

 Bractlet finely erose-dentate, or 2-lobed, or truncate and entire; 



spikelets strictly 2-flowered 18. Deschampsia. 



Bractlet cleft or 2-toothed, with the teeth sometimes produced 

 into awns; lowest flower awned; spikelets 2 to 6-flowered, often 



shining 19. Trisetum. 



Spikelets more than 5 lines long (excluding the awn); achene usually 

 adnate to its bractlet and palea, furrowed . . . 20. Avena. 

 Lower flower staminate, strongly awned from near the base: the upper 

 perfect, awnless or short-awned at the apex . . .21. Arrhenatherum. 

 Awn of the bractlet arising from between its lobes or teeth: the teeth in 

 many cases prolonged into straight awns . . .22. Danthonia. 



10. HOLCUS L. Velvet-grass. 

 Leaf-blades flat. Spikelets much laterally compressed, 2-flowered; 

 pedicels jointed below the bracts, so that these are readily deciduous 

 with the flower. Bracts 2, boat-shaped, keeled; lower 1-nerved; upper 

 larger, 3-nerved, notched, acute or sometimes shortly awned. Rachilla 

 shortly prolonged beyond the insertion of the uppermost flower- 



