GRAMINEA.E 



17 



2. S. linearis (Krook.) Nash. Smooth Crab-grass. Calms decum- 

 bent : leaves short, V-3' long, glabrous : spikes 2-6 : spikelets 1" long : 

 first glume -wanting : second glume as long as flowering one, hairy. — Com- 

 mon in sandy fields, especially along the Missouri River. July-October. 



3. S. sanguinalis (L.) Dulac. Crab-geass. Culms erect, ascending 

 or spreading, l°-3° long : leaves 2'-6' long : spikes 3-12, spreading : 

 spikelets 1 J" long : lowest glume present : second glume half as long as 

 the flowering one. — Growing everywhere in fields. July-October. 



8. PANICUM L. Panic Grass. 

 Spikelets with one pistillate and sometimes one additional staminate 

 flower. Glumes four, the three lower membranous, the two lower empty, 

 the third usually empty or sometimes bearing a staminate flower. Fourth 

 scale thick and shiny, inclosing a similar palet. 



Some or all the flowers awned. 

 Flowers never awned. 



All leaves similar ; panicle elongated. 

 Basal leaves shorter and broader than the culm 

 leaves ; panicle short. 



A. 

 Smooth throughout. 

 Spikelets 2" long. 

 Spikelets \"-\Y' long or less. 

 Spikelets f" long. 

 More or less pubescent, especially the lower 

 sheaths. 

 Spikelets 2" long or more. 

 Spikelets \l" long or less. 

 Panicle bearded in the axils. 

 Panicle not bearded in the axils. 



Culms stout anrt much branched. 15. P. capillare. 



Culms slender, branching only from base. 16. P. flexile. 



B. 

 Culm leaves long and linear. 

 Culm leaves lanceolate or broader. 

 Spikelets 1" long or less. 

 Leaves almost glabrous. 

 Leaves pubescent. 

 Axis of panicle long-pilose. 

 Axis of panicle almost smooth. 

 Spikelets more than V long. 

 Culm leaves broad and clasping at base. 

 Sheaths papillose-hispid. 

 Sheaths not papillose-hispid. 

 Sheaths hairy. 

 Sheaths glabrous. 

 Culm leaves lanceolate, hardly clasping at 

 base. 

 Spikelets nearly glabrous. 

 Spikelets very hairy. 



1. P. Crua-G-alli L. Barnyard Grass. A coarse grass l°-5° 

 high, with long rough leaves : spikelets imbricated, making the 5-15 

 2 



1. P. Cus-GalH. 



B. 



12. P. virgatum. 

 14. P. proHferum. 

 2. P. agrostoides. 



13. P. miliaceum. 

 17. P. cngnatum. 



11. P. perlongum. 



8. P. Kphaerocarpon. 



10. P. lanuginosum . 



9. P. unciphyllum . 



5. P. dandesiinum. 



3. P. Porterianum. 



4. P. macrocarpon. 



6. P. Scribnerianum. 



7. P. lAeiergii. 



