142 



GRAMINEAE. 



Panicle contracted, narrow, spike-like, the short branches rarely spreading. 

 \vering scale not awned but sometimes awn-pointed. 



Outer scales not awned, about half as long as the flowering scale, acute, i . Jf. sobolifera. 

 Outer scales long-acuminate, awn-pointed or awned. 



Outer scales about equal in length to the flowering scale, sharp-pointed, about i 

 long. 2. Jf. ^[e^:ica>la. 



Outer scales exceeding the flowering scale, generally twice its length, awned, about 



2'.-" long. 3. M. racemosa. 



Flowering scale long-awned; awn usually twice the length of the scale, sometimes shorter. 

 Outer scales about equalling the flowering scale. 



Basal hairs not more than one-half the length of the flowering scale. 



Spikelets consisting of 3 scales and i perfect flower. 4. .!/. svlvatica. 



Spikelets consisting of 4 scales, the third with a perfect flower, the fourth empt} 



and awned, 5. Jf. ambigua. 



Basal hairs as long as the flowering scale. 6. M. conidta. 



Outer scales one-half to two-thirds as long as the flowering scale. 7. Jf. tenuiflora. 



Outer scales less than one-quarter the length of the flowering scale. 



Lower scale minute, often wanting; flowering scale with an awn twice its length 



8. .If. diffusa. 

 Lower scale about two-thirds as long as the second; flowering scale with an awn fot 



times its length or more. 9. Jf. microsperma. 



Panicle open, its branches long and spreading. 



Culms i '/4 tall or more; panicle diffuse; leaves elongated, not rigid. 10. Jf. capillaris. 

 Culms i tall or less; leaves 2' long or less, rigid. 



Secondary branches of the panicle single; basal leaves short, numerous, stronglv recurved. 



11. Jf. gracillima. 

 Secondary branches of the panicle fascicled; basal leaves few, not recurved. 



12. Jf. pungens. 



i. Muhlenbergia sobolifera (Muhl.) Trin. Rock Muhlenbergia. (Fig. 320. ) 



Agrost 'is sobolifera Muhl.; Willd. Enum. 95. 1809. 

 Jftililfnbergia sobolifera Trin. Unifl. 189. 1824. 



Glabrous, culms 2-3 tall, erect, slender, simple, 

 or sparingly branched above, smooth. Sheaths 

 smooth, those of the culm shorter than the inter- 

 nodes, those of the branches overlapping and 

 crowded; ligule very short, truncate; leaves rough, 

 those of the culm 4 '-6' long, \y z "-$" wide, those 

 of the branches \'-$' long, about i" wide ; panicle 

 3'-6' in length, slender, its branches %'-\' long; 

 outer scales about y 2 " long, half to two-thirds the 

 length of the spikelet, equal, or the lower some- 

 what shorter, acute, scabrous, especially on the 

 keel; third scale scabrous, obtuse, 3-nerved, the 

 middle nerve usually excurrent as a short point 



Rocky woods, Massachusetts to Minnesota, south to 

 Virginia, Tennessee and the Indian Territory. Sept.- 

 Oct. 



2. Muhlenbergia Mexicana(L.) Trin. Meadow Muhlenbergia. (Fig. 321.) 



Agrostis Mexicana L. Mant. i: 31. 1767. 

 Agrostis filiformis Willd. Enum. 95. 1809. 

 Muhlenbergia Jfe.ricana Trin. Unifl. 189. 1824. 



Glabrous, culms 2-4 long, erect, or often prostrate, 

 much branched, smooth. Sheaths shorter than the 

 internodes, excepting at the extremities of the 

 branches, where they are crowded and overlapping, 

 smooth or scabrous ; leaves scabrous, those of the 

 culm 4 '-6' long, i"-$" wide, the branch leaves 

 smaller; panicle 2'-6" long, contracted, its branches 

 spike-like, I'-a' long, erect or appressed; spikelets 

 1 /<"-!>" long; outer scales somewhat unequal, ex- 

 ceeding the flowering one, or slightly shorter, acumin- 

 ate or short-awned, scabrous especially on the keel ; 

 third scale acuminate, scabrous, particularly toward 

 the apex. 



In swamps and borders of fields. New Brunswick to 

 yestern Ontario, south to North Carolina, Tennessee and 

 the Indian Territory. Aug. -Sept 



