82 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



2. Aristida dichotoma Michx. Poverty grass. 

 Sterile open ground ; frequent. Eastern U.S. 



3. Aristida gracilis Ell. 



Sterile open ground; infrequent. Eastern U. S. 



4. Aristida oligantha Mielix. 



Fields and open ground ; frequent. Southern states, north to N. J. 



18. STIPA L. Spear grass. 

 1. Stipa avenacea L. 



Dry or moist woods; frequent. May-June. Eastern U. S. 



Ripe fruit brown, the sharp point brown-bearded. 



19. MUHLENBERGIA Schreb. 



Panicle diffuse, the pedicels capillary 1. M. capillaris. 



Panicle contracted, usually narrow. 

 Culms delicate, decumbent at base, without rootstocks; glumes not over one-fourth 

 as long as the lemma. 



First glume obsolete; second glume minute 2. M. schreberi. 



First glume about one-fifth, the second about one-fourth as long as the lemma. 



2a. M. schreberi palustris. 

 Culms erect, from scaly rootstocks; glumes at least half as long as the lemma. 

 Blades ascending or erect; glumes narrow, acuminate, about as long as the body 

 of the lemma. 



Culms smooth below the nodes; lemma acuminate 3. M. inexicana. 



Culms pubescent below the nodes; lemma usually long-awned. 



4. M. umbrosa. 

 Blades divaricate; glumes broadly ovate, one-half to three-fourths as long as the 

 floret. 



Lemmas awned 5. M. tenuiflora. 



Lemmas awnless 6. M. sobolifera. 



1. Muhlenbergia capillaris (Lam.) Trin. Hair grass. 

 Rocky woods; infrequent. Eastern U. S. 



All our species of Muhlenbergia are late-flowering. 



2. Muhlenbergia schreberi J. F. Gmel. 



Open ground; common. Aug.-Sopt. Eastern U. S. (M. diffusa Willd.) 



This and the following species are sometimes called nimble Will and wire grass, 



because of the slender tough culms. 



2a. Muhlenbergia schreberi palustris Scribn. 

 Open moist grassland ; vicinity of Brightwood, the type locality. Also in III. 



3. Muhlenbergia mexicana (L.) Trin. 



Moist low woods and open ground; common. Northern states, south to N. C. 

 The scaly rootstocks of this and the following three species are conspicuous. 



4. Muhlenbergia umbrosa Scribn. 



Moist open ground and thickets; infrequent. Northorn states, south to N. C. ( M. 

 sylvatica Torr.) 



5. Muhlenbergia tenuiflora (Willd.) B. S. P. 



Moist rocky soil and moist woods; infrequent. Eastern U. S. ( M. willdenovii Trin.) 



6. Muhlenbergia sobolifera (Muhl.) Trin. 



Rocky woods; infrequent. Northern states, south to Va. 



20. BRACHYELYTRTJM Beauv. 



1. Brachyelytrum erectum (Beauv.) Schreb. 



Rocky or moist woods; infrequent. July-Aug. Northern states, south to Ga. (B. 

 aristatum Beauv.) 



