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A native of most tropical and many temperate climates, and has 

 been introduced into most cultivated fields, springing up or growing 

 after the cutting of wheat and early grain, and making its growth 

 in the latter part of the season. It is often associated with Setaria 

 glauca in stubble fields, and, like that species, furnishes a considera- 

 ble amount of fodder, which is as nutritions as Hungarian grass, 

 but not so productive. 



Cbnohkus, Linn. 



Spikelets much as in Panicum, inclosed 1 to 3 together in a thick, 

 coriaceous, spiny involucre, or bur, these arranged in an oblong or 

 cylindrical panicle. 



1. C. echinatus, Linn. North Carolina to Texas. 



2. C. incertus, M. A. C. (C. strictus, Chap.) Florida to North 



Carolina. 



3. C. myosuroides, H. B. K. Florida to Mexico. 



4. C. tribuloides, Linn. Massachusetts to Texas and California. 

 All the species of Cenchrus are found in sandy or saline grounds, 



and are called Bur-grass from the hard spiny seed involucre, which 

 renders the grass very troublesome and annoying both to man and 

 animals. They are very hurtful to the wool of sheep. The plants 

 are valueless. 



Pennisbtdm, Pers. 



Spikelets with one terminal perfect flower, and a second male or 

 neuter one below it, solitary, or two to three together, closely sur- 

 rounded by an involucre of usually numerous simple or plumose 

 bristles which disarticulate from the pedicel with the spikelets. 

 The spikelets are crowded in a spike-like panicle, or on peduncu- 

 lated spike-like branches. The lower empty glume is small, the 

 second and third larger, and longer than the perfect flower, the 

 glume of which is thicker and more rigid ; sterile flower consisting 

 of a membranaceous palet. 

 1. P. setosum, Rich? Florida. 



Spartina, Schreb. 



Spikelets one-flowered, much flattened, sessile along one side of 

 the long, triangular rhachis or spikes, which are racemose on the 

 panicle; outer glumes strongly compressed with a rigid keel, une- 

 2 



