POACEAE. 



23 



3. Chaetochloa geniculata (Lam.) 

 Millsp. & Chase. PERENNIAL FOX-TAIL 

 GRASS. (Fig. 30.) Perennial, by 

 rootstocks; culms tufted, l-2$ tall, 

 slender, compressed, rough below the 

 raceme: leaf-sheaths glabrous, com- 

 pressed; blades 4'-12' long, li"-4" 

 wide, the upper surface often with a 

 few long hairs at the base: racemes 

 dense, spike-like, l'-2' long, nearly 5" 

 in diameter, exclusive of the bristles, 

 the rachis pubescent: bristles 3"-5" 

 long: spikelets ovoid, acute, the flow- 

 ering scale acute, striate, finely trans- 

 versely rugose. [Panicum genicula- 

 tum Lam. ; Setaria glauca of Eeade, 

 Lefroy and Hemsley.] 



Common as a weed in waste and 

 cultivated grounds. Naturalized. Native 

 of the eastern United States and tropical 

 America. Flowers nearly throughout the 

 year. 



10. CENCHRUS L. 



Annual or perennial grasses, with 

 flat, convolute or eomplanate leaf- 

 blades and terminal spikes. Spikelets 2-6, in an ovoid 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 in- 

 volucres articulated to the rachis and readily deciduous, carrying 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. [Ancient Greek name 

 for some grass.] About 20 species in 

 temperate and tropical regions. Type 

 species: Cenchrus echinatus L. 



1. Cenchrus tribuloldes L. BUR- 

 GRASS. (Fig. 31.) Stems at first 

 erect, later prostrate and forming 

 mats, 8'-2 long, branching: leaf- 

 sheaths compressed; blades 2-} '-5' 

 long, 2"-4" wide, smooth or rough, 

 usually flat: spikes l'-2$' long: in- 

 volucres 6-20, 1V'-2V' broad, enclos- 

 ing 2 spikelets, pubescent, the spines 

 li"-2" long: spikelets 3"~3i" long, 

 usually not exserted beyond the in- 

 volucre. 



In sandy soil, especially on dunes 

 and beaches. Native. Eastern United 

 States. Flowers from spring to autumn. 

 Its burs perhaps brought to Bermuda 

 by ocean currents. Flowers from spring 

 to autumn. 



