104- FLORA. 



37. SPOROBOLUS R. Br. (See Appendix.) 



Perennial or rarely annual grasses, with flat or convolute leaves and open or 

 contracted panicles. Spikelets generally small, I -flowered, occasionally 2-3- 

 flowered. Scales in the I -flowered spikelets 3, membranous ; the 2 outer empty, 

 the first somewhat shorter ; the third scale equalling or longer than the empty ones; 

 palet 2-nerved. Stamens 2-3. Styles very short, distinct. Stigmas plumose. 

 Grain free, and often early deciduous. [Greek, referring to the deciduous grain.] 

 About 80 species, in tropical and temperate regions, very numerous in America. 

 Besides the following, 4 or 5 others occur in the southern and western U. S. 



Panicle contracted, spike-like. 



Spikelets more than 3.5 mm. in length. 



Panicle terminal; upper sheaths 7.5 cm. long or more. 

 Leaves glabrous or very nearly so. 



Third scale of the spikelet acuminate, much longer than the second and 



usually greatly exceeded by the palet. i. S. asper. 



Third scale of the spikelet acutish or obtuse, somewhat exceeding the 

 second and equalling or a little shorter than the palet. 



2. S. longtfolius, 



Leaves, at least the lower, papillose-hirsute. 3. S. pilosus. 



Panicles terminal and lateral ; sheaths 3.75 cm. long or less. 



4. S. vaginaeflorus. 

 Spikelets 3 mm. long or less. 



Sheaths inflated, the uppermost usually enclosing the base of the panicle. 



5. S. neglectus. 

 Sheaths not inflated ; panicle exserted. 



Branches of the panicle not crowded ; third scale acuminate. 



Outer scales of the spikelet obtuse or abruptly acute, less than half as 

 long as the third scale ; ligule about 2 mm. long, acutish. 



6. S. brevifolius. 

 Outer scales of the spikelet acuminate and awn-pointed, more than half 



as long as the third scale ; ligule less than 0.5 mm. long, erose- 

 truncate. 7. S. cuspidatus. 



Branches of the panicle densely crowded ; third scale acute. 



Culms decumbent and branched at the base, from a stout horizontal 



rootstock ; panicle short. 8. S. Virginicus. 



Culms erect, simple, tufted; panicle usually elongated. 



9. S. Indicus. 



Panicle open, its branches more or less spreading, at least at maturity. 

 First scale one-half as long as the second or less. 

 Branches of the panicle verticillate. 



Spikelets 1.5 mm. long, green. 10. S. argutus. 



Spikelets 2.5-3 mm - l n g> purple. n. S. gracilis. 



Branches of the panicle alternate or sometimes subverticillate. 

 Spikelets about 2 mm. long; first scale lanceolate. 



Pedicels equalling or shorter than the spikelets ; first scale acute. 



Sheaths naked or sparingly ciliate at the throat ; panicle usually 



exserted. 12. S. airoides. 



Sheaths densely pilose at the throat ; base of the panicle generally 



included. 13. S. cryptandrus. 



Pedicels much longer than the spikelets ; first scale narrow, acuminate. 



17. S. 7'exanus. 

 Spikelets 4-5.5 mm. long ; first scale subulate, usually awned. 



14. S. heterolepis. 

 First scale about equalling the second. 



Perennials ; culms from long rootstocks. 



Culms erect, simple ; leaves elongated. 15. S. Torreyanus. 



Culms decumbent and branched below ; leaves short. 



1 6. S. asperifolius. 

 Annuals ; roots fibrous, no rootstocks. 



Empty scales but little shorter than the flowering scale, usually pubescent. 



18. S. confusus. 

 Empty scales one-half as long as the flowering scale, glabrous. 



19. S, serotinus. 



I. Sporobolus asper (Michx.) Kunth. ROUGH RUSH-GRASS. (I. F. f. 341.) 

 Culms 6-15 dm. tall, erect. Leaves 7.5-35 cm. long, 2-4 mm. wide at the base, 



