Cenchrus L.
Inner involucral spines connate only at the base for up to a quarter of their length
Burr up to 7 mm long, usually purplish black when mature; bristles retorsely barbed. Spikelets usually 1 but up to 3 per burr. Tall or scrambling perennial usually with a knotted rootstock. Culms up to 2 m long or longer. Widespread. Open forests on poor soils. Fl. summer. Burr Grass Cenchrus caliculatus
Burr c. 12 mm long; bristles antrorsely barbed, one distinctly longer the others. Spikelets 2–5 per burr. Plants tufted, up to 80 cm high. Coast. Deep sands. Introd. from Africa and Asia. Fl. summer. Buffel Grass Cenchrus pennisetiformis