POACEAE 141 



the summit of the branches, and an inconspicuous inflorescence which is almost concealed 

 in the leaf-fascicles. Spikelets few, usually 3-flowered, almost sessile, in small clusters in 

 the axils of the floral leaves. Scales several, the 2 outer empty, persistent, narrow, acute, 

 hyaline, nerveless, the remaining ones 3-nerved, larger, entire, retuse, or 3-cleft at the 

 apex, the central nerve or all of them excurrent in a short tip, each of the lower scales 

 enclosing a narrow folded hyaline 2-keeled palet and a perfect flower, the upper scales 

 empty, similar to the flowering ones but smaller and narrower or sometimes with one re- 

 duced to 3 awns. Stamens 3. Styles elongated. Stigmas loosely and shortly plumose. 



1. Mtmroa squarrosa (Nutt. ) Torr. Stems 5-20 dm. long, tufted, erect to prostrate, 

 much branched : leaf -sheaths short, crowded at the nodes and ends of the branches ; blades 

 2.5 cm. long or less, 1-2 mm. wide, rigid, spreading, rough, pungently pointed : spikelets 

 2-5-flowered ; flowering scales 3-toothed, the teeth short-pointed or awned. 



On dry plains, South Dakota to Alberta, Nebraska, Texas and Arizona. Summer and fall. 



95. ARUNDO L. 



Tall perennial grasses, with thick stout somewhat woody stems, broad flat leaf-blades 

 and dense panicles. Spikelets 2-many-flowered, the rachilla-internodes glabrous. Scales 

 4-many ; empty scales narrow ; flowering scales broader, 3-nerved, hairy on the back. 

 Stamens 3. Styles distinct. Stigmas plumose. 



1. Arundo Donax L. Stems stout, erect, 3-6 m. tall : leaf-blades often 5 dm. long 

 or more and sometimes 4-5 cm. wide : panicle 5-8 dm. long, oblong : spikelets numerous, 

 crowded. 



Occasionally escaped from cultivation in the southern United States. Native of the tropical and 

 warmer regions of both hemispheres. Summer. 



96. FHRAGMITES Trin. 



Tall perennial grasses, with flat usually broad leaf -blades and ample terminal panicles. 

 Spikelets 2-several-flowered, the lower flower staminate, the remainder perfect, the rachilla 

 articulated between the flowers and covered with long silky hairs which surround the fertile 

 scales. Scales 4-several, glabrous, thin, narrow, acute, keeled, the 2 outer empty, the first 

 much shorter than the second, the remaining scales long-acuminate, the lowest one enclos- 

 ing a staminate flower, the remainder of the scales narrower and each containing a perfect 

 flower or the upper sometimes empty ; palet hyaline, much shorter than the scale, 2-keeled. 

 Stamens 3. Styles distinct, short. Stigmas plumose. 



1. Phragmites Phragmites ( L. ) Karst. Stems 1-5 dm. tall, stout, erect, from long 

 rootstocks: leaf -sheaths loose, overlapping; blades 1.5-3 dm. long or more, 1-5 cm. wide, 

 flat: panicle ample, 1.5-3 dm. long or more, its branches ascending: spikelets crowded, 

 the flowering scales 10-12 mm. long, long-acuminate. [P. communis Trin.] 



In swamps and wet places in almost all parts of North America north of Mexico. Also in Europe 

 and Asia. Summer and fall. COMMON REED. 



97. TRIDENS K. & S. 



Usually perennial grasses, with flat or involute leaf-blades and the inflorescence com- 

 posed of open or contracted and sometimes spike-like panicles. Spikelets 3-many-flowered, 

 the flowers perfect or the upper ones staminate. Scales 5-many, membranous, sometimes 

 firmer, the 2 lower empty, keeled, obtuse to acuminate, usually shorter than the rest, some- 

 times longer : flowering scales 3-nerved, the midnerve or all the nerves excurrent, the 

 midnerve and the lateral nerves or the margins pilose, the apex entire or shortly 2-toothed, 

 the teeth obtuse to acute, the callus short and obtuse ; palet shorter than the scale, com- 

 pressed, 2-keeled. Stamens 3. Styles short, distinct. Stigmas plumose. 

 A. Panicle open, the branches long and more or less spreading. 



Lateral nerves of the flowering scale vanishing at the margin, not excurrent. 

 Spikelets 4-5 mm. long, the nerves of the palet not abruptly gibbous below 



the middle. 1. T. eragrostoides. 



Spikelets 8-10 mm. long, nerves of the palet abruptly and strongly gibbous 



below the middle. 2. T, Texanus. 



Lateral nerves manifestly excurrent in short projections. 

 Spikelets oval, more than % as broad as long 



Spikelets 7-9-flowered, 5 mm. long : palet rounded at the decidedly apic- 



ulate apex, the nerves ciliolate, the internerve broadly ovate-oval. 3. T. amUguus. 

 Spikelets 4-6-flowered, 6-7 mm. long : palet obtuse at the apex, the nerves 



ciliate, the internerve elliptic or nearly so. 4. T. Langloisii. 



Spikelets elliptic to linear-oblong, less than % as broad as long. 5. T. seslerfoidev. 



