2. Polypogon interruptus H.B.K. Ditch polypogon. Fig. 113. 



Perennial; culms rooting at the lower nodes, 2-10 dm. long, 1-4 mm. thick; 

 ligule a scale 4—10 mm. long; blades 4-22 cm. long, 2-12 mm. broad; panicle 

 3-20 cm. long, 1-5 cm. thick, occasionally narrowed and somewhat spikelike but 

 usually broad, interrupted, with whorled branches 1-5 cm. long; glumes 2 mm. 

 long, apically entire, each bearing an awn about 2 mm. long; lemma a little longer 

 than 1 mm. with a deciduous awn 2-3 mm. long. 



Calcareous mud along streams and irrigation ditches and low wet places, in 

 Okla. (Waterfall) and on Tex. Edwards Plateau, rare (known only from Val 

 Verde Co.), to Ariz. (Apache, Navajo, Coconino, Santa Cruz and Pima cos.), Apr.; 

 widespread in temp. N. A. and S. A., n. to B.C. and Neb. 



3. Polypogon elongatus H.B.K. Fig. 1 14. 



Perennial; culms erect or often decumbent at base, glabrous, rather stout, as 

 much as 1 m. tall; sheaths glabrous, somewhat nerved, lacerate at the rather 

 broad summit, to 8 mm. long; blades scabrous on the margins, glabrous or some- 

 what scabrous on the surfaces, to 20 cm. long and 1 cm. wide; panicle erect, in 

 ours rather dense and spikelike but somewhat interrupted in the lower part, 

 15-30 cm. long, the branches closely flowered to base; glumes hispidulous 

 (especially on keel), 2-3 mm. long, gradually narrowed to an awn 2-3 mm. 

 long; lemma 1.5 mm. long, the awn arising from below the tip, 1-2 mm. long or 

 sometimes obsolete. 



In salt marshes, along streams and ditches, in Ariz. (Santa Cruz and Pima cos.); 

 also Mex. to Arg. 



31. Phleum L. 



Annuals or perennials with erect culms, flat blades and dense cylindric panicles; 

 spikelets 1 -flowered, laterally compressed, disarticulating above the glumes; glumes 

 equal, membranaceous, keeled, abruptly mucronate or awned or gradually acute; 

 lemma shorter than the glumes, hyaline, broadly truncate, 3- to 5-nerved; palea 

 narrow, nearly as long as the lemma. 



A genus of 15 species in temperate Eurasia, North America and South America; 

 probably all Eurasian in origin. 



1. Culms mostly more than 5 dm. tall, erect from a swollen bulblike base; panicle 

 narrow, several times longer than wide 1. P. pratense. 



1 . Culms 2-5 dm. tall, from a decumbent somewhat creeping base; panicle 

 usually not more than twice as long as wide, bristly.. ..2. P. alpinum. 



1. Phleum pratense L. Timothy. Fig. 1 15. 



Perennial from very short bulbously thickened rhizomes; aerial culms 5-10 dm. 

 long, 2-3 mm. thick, the lowest internodes often reclining, otherwise erect, leafy; 

 ligule a thin scale 2-4 mm. long; blades 6-26 cm. long, 5-10 mm. broad, tapered 

 to a long point, flat; panicle 5-20 cm. long, 5-8 mm. thick, terete, spikelike; 

 spikelets 1 -flowered, strongly laterally compressed; glumes equal 3-3.5 mm. long, 

 oblong, hyaline but each with a firm keel prolonged into a short spreading awn, the 

 keel ciliate; zone of abscission between the glumes and the lemma; lemma and 

 palea about half as long as the glumes, hyaline, the palea very narrow. 



Occasional as a waif in marshes, wet meadows, seepage areas and in mud along 

 streams, in the e. half of Tex., not persisting, brought in with hay, and N. M. 

 (Colfax, Otero, Santa Fe, San Miguel and Sandoval cos.) and Ariz. (Coconino and 

 Apache, s. to Graham and Pima cos.), summer; widespread in moist temp, parts 

 of N. A., introd. from Euras. 



2. Phleum alpinum L. Alpine timothy. Fig. 1 15. 



Culms 2-6 dm. tall, glabrous, from a decumbent somewhat creeping densely 



240 



