Genus 40. GRASS FAMILY. 



14. Sporobolus airoides Torr. Hair-grass Dropseed. Fig. 477. 



Agrostis airoides Torr. Ann. Lye. N. Y. 1 : 151. 1824. 

 5. airoides Torr. Pac. R. R. Rept. 7: Part 3, 21. 1856. 



Culms ii°-3° tall, erect, simple, smooth and glabrous. 

 Sheaths generally shorter than the internodes, some- 

 times sparsely ciliate at the throat; ligule very short; 

 blades smooth beneath, scabrous above and sometimes 

 sparingly hairy near the base, 4"-iJ" wide at the base, 

 attenuate into a long slender involute point, the basal 

 about one-half as long as the culm, the upper culm 

 leaves 2'-s' in length; panicle 5-15' long, usually ex- 

 serted, the branches alternate or the upper verticillate, 

 at length widely spreading, the lower 3'-/ long; spike- 

 lets l"-i" long, the scales acute, . glabrous, the outer 

 unequal, the lower one about half as long as .the upper; 

 third scale equalling the second and the palet. 



Prairies, Nebraska to Montana, California and Texas. 

 Rush-grass. Salt-grass. Fine-top salt-grass. Aug.-Sept. 



15. Sporobolus cryptandrus (Torr.) A Gray. Sand Dropseed. Fig. 478. 



i 99 



Agrostis cryptandra Torr. Ann. Lye. N. Y. i: 151. 

 Sporobolus cryptandrus A. Gray, Man. 576. 1848. 



1824. 



Culms ii°-34° tall, erect, simple or sometimes branched 

 at the base, smooth and glabrous. Sheaths smooth, with 

 a dense pilose ring at the summit, the lower short, crowded 

 and overlapping, the upper much longer, generally enclos- 

 ing the base of the panicle; ligule a ring of short hairs; 

 blades 3'-6' long, i"-2" wide, flat, glabrous beneath, sca- 

 brous above, long-acuminate; panicle 6'-io' in length, the 

 base generally included in the upper sheath, rarely entirely 

 exserted, the branches spreading or ascending, alternate, 

 the lower iJ'-3' long; spikelets i"-ii" long, the scales 

 acute, glabrous, the outer scabrous on the keel, the lower 

 one-third as long as the upper ; third scale somewhat longer 

 or shorter than the second. 



In sandy soil, Massachusetts to Montana, Pennsylvania and 

 Mexico. Prairie-grass. Aug.-Oct. 



16. Sporobolus heterolepis A. Gray. Northern Dropseed. Fig. 479. 



Vilfa heterolepis A. Gray, Ann. Lye. N. Y. 3 : 233. 1835. 

 Sporobolus heterolepis A. Gray, Man. 576. 1848. 



Culms i°-3° tall, erect, simple, smooth and glabrous. 

 Sheaths sometimes sparingly pilose at the summit, the 

 lower short, loose, and overlapping, the upper much 

 elongated and tight to the culm; ligule a ring of short 

 hairs; blades involute-setaceous, glabrous, the margins 

 and upper part of the midrib very rough, the basal about 

 three-fourths the length of the culm, occasionally equal- 

 ling it, those of the culm shorter; panicle 3'-lo' in length, 

 its branches erect or ascending, alternate or sub-verticil- 

 late, the lower ii'-3i' long; spikelets 2"-2l" long, the 

 scales smooth and glabrous, the outer unequal, acuminate, 

 the lower subulate, about half the length of the broad 

 second one, often awn-pointed ; third scale obtuse or 

 acute, shorter than the second or occasionally equalling it. 



In dry soil, Quebec to Saskatchewan, south to Connecti- 

 cut, Pennsylvania, Missouri and Texas. Bunch-grass. Aug.- 

 Sept. 



