46 



P DALES 



Colorado. 



6. Muhlenbergia sylvatica Torr. 



In woods along streams. Ewing; Orleans; Valentine. 



7. Muhlenbergia tenuifolia (Willd.) B. S. P. 

 Grand Island; Red Cloud. 



8. Muhlenbergia diffusa Willd. 



In dry soil in the southeastern part of the state. Lincoln; Red 

 Cloud; Valley County. 



9. Muhlenbergia pungens Thurb. 



In the sand-hills, frequently in "blow-outs." Belmont; 

 Haigler; Hat Creek Basin; Minden; Mullen; Valentine. 



Biow-out grass. 



Dismal River; 



13. Stipa. 96. 



Empty scales less than 1 cm. long. 1. S. viridula. 

 Empty scales over 1 cm. long. 



Flowering scales, without awn, 8 to 12 mm. long. 2. S. comata. 



Flowering scales, without awns, 20 to 25 mm. long. 3. S. spartea. 



1. Stipa viridula Trin. 



In the western part of the state. Belmont; Burwell; Central City; 

 Deuel County; Mullen; Valentine; Weigand. 



2. Stipa comata Trin. & Rupr. Western spear-grass. 

 Common in the western part of the state and in the sand-hills. Axtell; 

 Belmont; Box Butte County; Broken Bow; Brunswick; Harrison; 

 Halsey; Kearney County; Thedford; Valentine. 



3. Stipa spartea Trin. Spear-grass. 

 Common in prairies in the eastern part of the state. Crete; Cherry 

 County; Lincoln; Thedford; Weeping Water. 



14. Aristida. 93. 



Central awn 3.5 cm. long or more. 

 Awns distinct to the base, not articulated to the scale. 

 First scale much shorter than the second. 



Second scale 1.5 cm. long, but little longer than the flowering 



scale. 4. A. fendleriana. 



Second scale 2 cm. long, much longer than the flowering scale. 



5. A. longiseta. 

 First scale as long as the second or nearly so. 6. A. oligantha. 

 Awns united at the base and articulated to the scale. 



8. A. tuberculosa. 

 Central awn not over 3 cm. long. 

 Lateral awns much shorter than the central one. 



Spikelets 10-15 mm. long. 2. A. basiramea. 



Spikelets about 6 mm. long. 



Central awn 1 cm. or more long, the lateral 2-6 mm. long. 



7. A. gracilis. 

 Central awn 3-6 mm. long, the lateral erect teeth. 



1. A. dichotoma. 

 Lateral awns nearly as long as the central one. 



First scale shorter than the second and third. 3. A. fasciculata. 

 First scale longer than the second and third. 9. A. purpurascens. 



