40 



Fig. 26. Cenchrus tribuloides L. SAND BUR.— a, A spiny bur which in- 

 closes the spikelets; b, a section of the same showing the spikelets within; 

 c, a lateral view of one of the spikelets showing the several glumes. Figures 

 404 to 407 in Bui. 17 illustrate other species of this genus. 



26. CENCHEUS Linn. Sp. PI. 1049. 1753.— Spikelets 1-flowered hermaphro- 

 dite (rarely with a male flower below the perfect terminal one) , 1-4 together 

 with an ovoid or globular involucre of rigid more or less connate bristles form- 

 ing spiny burs or false capsules, these sessile or nearly so in simple terminal 

 spikes, or racemes, falling off with the spikelets. Glumes as in Panicum awnless. 

 Grain free within the slightly hardened fruiting glume and palea. Annual 

 or perennial grasses with spreading or erect culms bearing few or many more 

 or less crowded " burs " in terminal spikes. 



Species about 12. in the tropical and warmer temperate regions of both 

 hemispheres. 



