25 



17. Side bristles of the awn sparingly ciliate ... A. lutescens. 

 All the bristles of the awn plumose 18 



18. Awn tardily disarticulating with the tip of the valve. 



A. capensis. 



Awn readily deciduous with the upper half of the 



valve 19 



19. Suffrutescent. Spikelets 6-7 lin. long. Middle bristle 9-12 



hn. long A. namaquensis. 



Not suffrutescent. Spikelets up to 4 lin. long. Middle 

 bristle 3-4 lin. long A. proxima. 



20. Lower glume rather longer than the upper 21 



Lower glume shorter than the upper 22 



21. Annual, about i in. high. Panicles J in. long ... 



A. subacaulis. 

 Perennial, 3-12 in. high. Panicles i-6 in. long. A. obtusa. 



22. Panicle narrow, rather lax, not spike-like 23 



Panicle spike-like 24 



23. Calms iJ-2 ft. 4 noded. Awn plumose from below 



branching point A. uniplumis. 



Culms i ft. 1 noded. Middle awn plumose in the upper 

 half * A. dregeana. 



24. Culms up to J ft. Panicle hairy A. gcminifolia. 



Suffrutescent. Panicle glabrous A. brevifolia. 



ATROPIS. 



Leaves i-i^ lin. broad when expanded. Panicles ovate 

 to subdeltoid with rather coarse and stiff spreading 

 branches A. borreri. 



Leaves up to | lin. broad. Panicle linear, with erect 

 finely filiform to capillary branches ... A. angusta. 



A VENA. 



1. Valves glabrous or hairy at the base only. Rachilla 



tough or tardily disarticulating A. sativa. 



Valves hairy to or beyond the middle. Rachilla readily 

 disarticulating 2 



2. Spikelets 15-20 lin. long. Rachilla glabrous between the 



valves A, sterilis. 



Spikelets 9-14 lin. long. Rachilla villous between the 

 valves 3 



3. Valves shortly bifid A. fatiia. 



Valve lobes produced into long bristles ... A. bafbata. 



