POACEAE. 19 



2. C. verticillata (L.) Scribn. Stems 3-6 dm. tall, erect or ascending: leaf- 

 blades 7-18 cm. long, 6-12 mm. wide: bristles flexuous, 3-3 mm. long: spikelets 

 narrowly elliptic-ovate, acute, 2-2.5 mm. long, the flowering scale rounded at 

 the shortly apiculate apex, smooth, or with very fine transverse wrinkles below 

 the middle. — M. Eather rare, in waste places and cultivated grounds. Nat. 

 of Eu. — ■ Limestones. — Sum. 



3. C. viridis (L.) Scribn. Stems tufted, 2-9 dm. tall: leaf -blades 3 dm. long 

 or less, 4-10 mm. wide: panicles 2-10 cm. long, green: bristles 1-1.5 cm. long: 

 spikelets about 2 mm. long, elliptic. — Common, in waste and cultivated grounds. 

 Nat. of Eu. — Sum. and fall. — Bottle-grass. 



4. C. italica (L.) Scribn. Stems simple, or branched at the base: leaf -blades 

 long-acuminate, 2^ dm. long, 1.5-3 cm. wide, rough: panicles dense, cylindric, 

 S-20 cm. long, 2-3 cm. in diameter, obtu?e or truncate at both ends: bristles 

 1-3, 3-10 mm. long, often shorter than the spikelets or nearly wanting: spike- 

 lets elliptic, 2.5-3 mm. long. — Eather rare, in fields and waste places. Nat. 

 of Eu. — Sum. and fall. — Hungarian-grass. 



10. CENCHRUS L. Annual or perennial grasses, with flat, convolute or 

 complanate leaf-blades and terminal spikes. Spikelets 2-6, in an ovate or 

 globose involucre, consisting of two thick hard valves which are exteriorly armed 

 with stout spines and sometimes also with basal bristles which are thickened at 

 the base, the involucres articulated to the rachis and readily deciduous, carry- 

 ing the persistent spikelets with them. Scales 4, awnless, the first and second 

 empty, the first small or minute, the third equalling or longer than the second, 

 enclosing a palet and also sometimes a staminate flower, the fourth scale 

 chartaceous, firmer, enclosing a palet of similar texture and a perfect flower. 

 Stamens 3. Styles often connate at the very base. Stigmas plumose. 



1. C. carolinianus Walt. Stems at first erect, later prostrate and forming mats, 

 2-6 dm, long, branching: leaf -blades 6-12 cm. long, 4-8 mm. wide: spikes 3-6 

 cm. long: involucres 6-20, 3-5 mm. broad, enclosing 2 spikelets, pubescent, 

 the spines 3-4 mm. long : spikelets 6-7 mm. long. — Eather common, in sandy 

 soil. — Sum. and fall. — Bur-grass. Sand-bur. Sand-spur. Cockspur. 



11. ZIZANIA [Gronov.] L. Tall robust annual monoecious aquatic grasses, 

 with broad flat leaf -blades and ample terminal panicles. Spikelets of two kinds, 

 articulated below the scales, 1-flowered, each with a more or less prominent 

 cartilaginous ring at the base, narrow, the staminate readily deciduous, on the 

 more or less spreading lower branches, the pistillate tardily deciduous, on the 

 erect or appressed upper branches of the panicle. Scales 2, the first empty, the 

 second enclosing a flower but no palet: scales of the staminate spikelets mem- 

 branous, concave, acute or awn-pointed ; those of the pistillate spikelets linear, 

 firmer, involute, the first long-awned, longer than the awn-pointed second. 

 Stamens 6. Styles nearly distinct. Stigmas plumose with short hairs. 



1. Z. aquatica L. Stems 1-3 m. tall: leaf -sheaths smooth and glabrous; blades 

 1.5-8 dm. long, 5-25 mm. broad, usually rough: panicle 2-3 dm. long: staminate 

 spikelets 7-8 mm. long: pistillate spikelets 12-20 mm. long, the awn 2.5-5 cm. 

 long. — Susquehanna valley. On the shores of the river and low islands. — 

 Sum. and fall. — Wild-rice. Indian-rice. Water-oats. 



12. HOMALOCENCHRUS Mieg, Grasses of wet situations, with flat 

 leaf-blades and usually open, rarely contracted, terminal panicles, the branches 



