Ill 



52 TRIANDRIA DIGYNIA 



scabrous. Spikelets clustered, on short pedicels. Bristles of the involucre . 

 pairs, retrorsely scabrous, about twice as Ion-: as the spikclets, yellowish green, 

 sometimes purplish. Abortive floret neutral ; upper palca small. Paha of th t . 

 perfect floret roughish-punctatc, so as to appear papillate. 



Hab. Gardens, and cultivated lots: West Chester : not common. F/.July. Fr.Ang. 

 Obs. The rctrorse teeth on the bristles of this species render the spikes some. 

 what adhesive to objects with which they come in contact. Four other species are 

 enumerated in the U. States : of which the S. itulira, w Ith very large spikes, grows 

 along the river Delaware. The others are Southern plants. None of them possess 

 any value to the Agriculturist, except the S. germanua. 



29. CENCHRUS. L. Mttt. Gen. 58. 

 [Greek, Kerichros, Millet: probably applied l»y the ancients to another plant.] 



Inflorescence racemose : Spikclets 1 to 3, enclosed in a laciniate, eclii- 

 nate, cartilaginous Involucre. Glumes 2, unequal, the lower one 

 smaller. Florets dissimilar ; the lower one Staminate, the other Per- 

 fect. Styles 2, united at base. 



1. C. tribuloides, Z. Involucres globose, pubescent, muricate-spi- 



nose, split on one side, enclosing 2 or 3 spikclets, each one or two-flow- 



ered. Beck, Bot. p. 390. 



C. echinatus, var. tribuloides, Torr. FL 1. p. 01). Eat* Man* p. 86, 



Also? C. echinatus. MuhL and other American Botanists, 



Tin bulls-like Cenchrus. Yulgd — Bur-grass. Hedge-hog Grass. 



Root annual, fibrous. Culm decumbent, i to 2 feet l ong* geniculate, branching 

 glabrous. Leaves lanceolate, acuminate, rather short, slightly scabrous on uic 

 margin: sheaths loose, smooth ; ligule bearded. Raceme terminal, of G to 12 or 14 

 alternate, involucrate heads, or clusters; rachis angular, flexuose, slightly scab- 

 rous (pilose, Muhl. Torr. and Ell.)- Involucre urceolate, or globose, laciniate, 

 usually split to the base on one tide, hairy, armed with ritiid, subulate, scabrous 

 spines; villous within ; including 1,2, 6r3sptft*fefs,each 1 or '2- flowered. (Humes 

 unequal, herbaceous. Abortive floret* mostly staminate ; pulcee membranaceous. 

 Perfect florets lance-ovate, acuminate; palea subcartilaginuus, nerved, smooth. 

 Seed compressed, orbicular-ovate, brown. 

 Hab. Mica-slate hills, near Jno. D. Steele's : rare. FL Aug. Fr. September. 



Obs. Prof. Torrey expresses the opinion (in Litt.) that " it is doubtful whether 

 the true C. echinatus inhabits N. America ; our two species (as some call them) be- 

 ing merely forms of C tribuloides' 1 The prickly involucres are a grievous pest, 

 wherever this grass prevails in cultivated grounds, or about houses. It is fortu- 

 nately quite rare, as yet, in Chester County. It is believed to be the only species 

 of the genus in the U. States ; and was first observed, here, by Mr. Joshua Hoopus, 

 in 1833. 



Div. II. Stipace;e — Stipa, or Feather-grass Tribe. 



Inflorescence Panicled. Spikclets solitary, 1 flowered. Glumes membrana- 

 ceous* Palese mostly 2 ; lower one coriaceous, involute, owned. 



30. ARISTIDA. L. Mat. Gen. 85. 

 [Latin, Arista, an Awn, or beard; characteristic of the genus.] 



Glumes 2, membranaceous, unequal, Palex mostly 2, pedicellate ; 

 lower one coriaceous, involute, 3-awned at the tip ; upper one very mi- 

 nute, or obsolete. 



