Cbnchrus. GRAMINEyE. 431 



13. CENCHRUS. Linn, {'in Y>s.n); Endl. gen. 783. hedgehog grass. 



[ From the Greek, kcnchros, millet ; but wliy applied to this genus, Is not evident] 



Spikelets 2-flowered, solitary, in pairs, or more, enclosed in a cleft spiny or bristly involucre 

 which becomes indurated in fruit. Glumes 2, unequal, membranaceous. Lower flower 

 staminate or neuter, membranaceous, with 1 or 2 paleae : upper flower perfect, somewhat 

 coriaceous. Styles united at the base. — Mostly annual branching grasses, with flat leaves 

 and terminal spikes. 



1. Cenchrus tribuloides, Linn. Bur-grass. HedgeJiog Grass. 



Involucres globose, pubescent, muricate-spiny, mostly split on one or both sides, enclosing 

 2-3 spikelets. — Linn. sp. (ed. 2.) 2. p. 1488 ; Vahl, enum. 2. p. 395 ; Michx. fl.\.p.G\; 

 Muhl. gram. p. 52 ; Ell. sk. 1. p. 93. t. 4./. 3 ; Trin. diss. 2. p. 74 ; Beck, hot. p. 399 ; 

 Kunth, enum. 1. p. 166 ; Darlingt. fl. Cest. p. 52. C. echinatus, Muhl. gram. I. c. ; Torr. 

 fl. I. p. 68 (and var. tribuloides), not of Linn. C. Carolinianus, Walt. fl. Car. p. 79. 



Culm erect or procumbent, 1-2 feet long, geniculate and branching at the base. Leaves 

 flat, three lines wide : sheaths smooth, bearded at the throat. Spikes about two inches long, 

 consisting of 8 - 10 sessile bur-like heads. Involucre beset with rigid retrorsely scabrous 

 spines, more or less pubescent and whitish, split (when old) nearly to the base in one or two 

 places, almost wholly enclosing the spikelets. Lower flower neuter. Glumes ovate-lanceolate, 

 5-nerved. Paleae of the perfect flower somewhat cartilaginous. Caryopsis roundish-ovate. 



Dry sandy soils, particularly near the salt water ; in the latter situation, the spikes are 

 whitish : common near New- York, and on Long Island. A troublesome weed in some places, 

 on account of the adhering prickly burs. 



Tribe IV. STIPACEJE. Kunth. 



Spikelets one-flow ered. Lower palea involute, mostly indurated in fruit, aiuned at the tip ; 

 the aivn simple or 3-cleft, mostly twisted and articulated at the base. Ovary more or 

 less stipitate. Scales mostly 3. 



14. ORYZOPSIS. Michx. fl. I. J). 51. t. 9. mountain niCE. 



PiPTATnERUM, Beauv.; Urachne, TVin. 

 [ From the Greek, onjza, rice, and opsis, resemblance.] 



Glumes herbaceo-membranaceous, equal, awnless. Paleae elliptical, nearly equal, coriaceous, 

 with an articulated awn at the tip. Scales linear or lanceolate, as long as the ovary. Styles 

 sometimes united at the base. — Erect perennial grasses, with the inflorescence paniculate. 



