WOOTON AND STANDLEY FLOEA OF NEW MEXICO. 43 



13. POACEAE. Grass Family.^ 



Fibrous-rooted annual or perennial herbs, often with rootstocks, with jointed, 

 usually hollow, cylindrical stems and 2-ranked leaves, their blades parallel-veined, 

 mostly long and narrow, their bases forming an open or rarely a closed sheath around 

 the stem; inflorescence an open or spikelike panicle, a raceme, or a spike; flowers 

 usually perfect, small, without a distinct perianth, arranged in spikelets, these con- 

 sisting of an articulate axis (rachilla) and 3 to many 2-ranked bracts, the lower 2 

 (glumes) being empty, the succeeding 1 or more (lemmas) each containing in its 

 axil a single flower subtended by a palea; stamens usually 3; pistil 1, with a 1-celled, 

 l-o\Tiled ovary, 2 styles, and plumose stigmas; fruit a caryopsis with a starchy endo- 

 sperm and a small embryo. 



KEY TO THE TRIBES. 



Spikelets dorsally compressed, falling from the pedicels entire, 1-flowered, or some- 

 times with a rudimentary flower below the perfect one. 

 Lemma and palea hyaline, much more delicate in texture than the glumes. 



Spikelets unisexual, the pistillate borne in the lower, the staminate in the 



upper part of the same spike I. MAYDEAE. 



Spikelets in pairs, one sessile, the other pedicellate, the former perfect, the 

 latter perfect or with a staminate flower, often reduced to 1 or 2 



scales II. ANDROPOGONEAE. 



Lemmas, at least those of the perfect flowers, similar in texture to the glumes 

 or thicker and firmer, never hyaline. 

 Lemma and palea membranous; spikelets in groups of 3, these falling together 



from the continuous axis III. ZOYSIEAE. 



Lemma and palea chartaceous to coriaceous, different in color and texture 



from the glumes; spikelets various IV. PANICEAE. 



Spikelets laterally compressed, at least at maturity, the glumes usually persistent on 

 the pedicel or rachis after the fall of the florets, 1 to many-flowered, the rudi- 

 mentary flower, if any, usually uppermost. 

 Spikelets in 2 rows, sessile or nearly so. 



Spikelets on one side of the continuous axis, forming one-sided spikes, these 



digitate or paniculate Vni. CHLORIDEAE. 



Spikelets alternate on opposite sides of a channeled, sometimes articulate, 



axis; spikes solitary X. HORDEAE. 



Spikelets borne in an open or spikelike panicle or raceme, usually upon distinct 

 jiedicels. 

 Spikelets with 1 perfect flower. 



No rudimentary or staminate floret below the perfect one. 



V. PHALARIDEAE. 

 A pair of rudimentary or staminate florets below the perfect one. 



VI. AGROSTIDEAE. 

 Spikelets 2 to many-flowered. 



Lemmas usually shorter than the glumes; awn dorsal or from between the 



teeth of the bidentate apex, usually bent VII. AVENEAE. 



Lemmas usually longer than the glumes; awn terminal (rarely dorsal 

 in Bromus) and straight, or none IX. FESTTJCEAE. 



^ For a more extended accoiint of New Mexican grasses from an economic stand- 

 point, see Wooton and Standley, N. Mex. Agr. Exp. Sta. Bull. 81. 1912. 



