58 



GRAMIXEJE. 



Bractlet hairy; rachilla naked 26. Arundo. 



Bractlet naked; rachilla hairy -27. Phragmites. 



B. Rachilla and bractlet naked, or if hairy the hairs much shorter than the 

 bracts and bractlet; stigmas (in ours) plumose, comparatively short, either 

 sessile or raised on a short style, protruding from the sides of the bractlet. 

 Spikelets of two kinds at each node, very dissimilar in form, one perfect and 

 1 to 3-floweied; the ochers sterile and composed of many empty braetlets. 

 Perfect spikelets 1-flowered, the sterile consisting of about 10 eniptv bractlets 



which are obtuse 35. Lamarckia. 



Spikelets alike in form though sometimes dioecious. 

 Flowers dioecious; rootstocn perennial. 

 Spikelets 8 to 16-flowered; rootstock very stout and creeping, scaly; panicle 



dense, ovoid; grasses of salt-marshes or alkali soils . . 32. Distichlis. 

 Spikelets 2 to 6 flowered; rootstock tufted or if creeping then long and 



slender 36. Poa. 



Flowers all perfect, or perfect and imperfect in the same spikelet. 

 Bracts and bractlets awnless. 

 Bractlet 1 to 3-nerved. 

 Annuals; panicle more or less lax; spikelets many (sometimes 70)- 

 flowered, the flowers densely imbricate; palea persistent after the 



bractlet and achene have fallen . . 28. Eragrostis. 



Perennials; panicle contracted and spikelike, dense or slightly inter- 

 rupted, silvery shining; spikelets 2 to 7 (rarely only l)-flowered. 



29. Kceleria. 



Bractlet 3 to 5-nerved. 

 Perennials; uppermost flower-enclosing bractlet enwrapping 1 to 3 

 smaller empty bractlets, which in ours are truncate-clavate . . . . 



30. Melica. 



Bractlet 5 to many-nerved. 

 Spikelets large, flattened, ovate, somewhat cordate at base; bractlet very 



obtuse, concave, becoming ventricose; annuals . . 33. Briza. 

 Spikelets not cordate, mostly smaller. 

 Bractlet laterally compressed, mostly keeled, the margins or nerves 

 below clothed with cobwebby hairs, or pubescent, its lateral nerves 

 arched, converging above toward the mid-nerve. 36. Poa. 

 Bractlet rounded on the back, at least below, naked at the base, its 

 lateral nerves nearly parallel, scarcely or not at all converging. 



37. Panicularia. 



Either bracts or bractlets awned, awn-pointed or mucronate (in Kceleria). 

 Palea with conspicuously toothed marginal wings on the keels; bractlet 

 with a straight, rigid awn; annuals of wet meadows, with weak 



stems, and pale greenish-yellow foliage 31. Pleuropogon. 



Palea without marginal wings on the keel. 

 Panicle contracted and spikelike, dense or slightly interrupted, silvery- 

 shining 29. Kceleria. 



Panicle 1-sided, glomerate or interrupted; spikelets in dense, 1-sided 



fascicles 34. Dactylis. 



Panicle more or less lax; not dense and spikelike. 

 Stigmas plainly arising at or near the apex of the ovary; ovary and 

 achene in most cases smooth; bractlet not notched or 2-lobed, 



usually awned or awn-pointed 38. Festuca. 



Stigmas plainly arising below the apex of the ovary, on the anterior 

 portion; ovary and achene crowned by a little appendage or tuft 

 of short hairs; achene always adnate to the palea; bractlet usually 

 distinctly notched or shortly 2-lobed at the apex, with an awn 

 between the notches 39. Bromus. 



26. ARUNDO L. 



Perennial reeds; stems tall, stout, erect. Leaf-blades broad, flat. 

 Spikelets 2 to 6-flowered, in a dense and somewhat spreading panicle. 

 Bracts somewhat unequal, keeled, 3-nerved. Rachilla naked, jointed 

 above the bracts and between the flowers. Flowers crowded, all 

 perfect or the upper staminate. Bractlet slender, 2-toothed and with 



