142 GRAMINEAE. 
Panicle contracted, narrow, spike-like, the short branches rarely spreading. 
Flowering scale not awned but sometimes awn-pointed. 
Outer scales not awned, about half as long as the flowering scale, acute. 1. J/. sobolifera. 
Outer scales long-acuminate, awn-pointed or awned. 
Outer scales about equal in length to the flowering scale, sharp-pointed, about 1'4/’ 
long. : 2. M. Mexicana. 
Outer scales exceeding the flowering scale, generally twice its length, awned, about 
2'4"' long. 3. MW. 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 1 perfect flower. 4. M. sylvatica. 
Spikelets consisting of 4 scales, the third with a perfect flower, the fourth empty 
and awned, . M. ambigua. 
Basal hairs as long as the flowering scale. . M. comata. 
Outer seales one-half to two-thirds as long as the flowering scale. . M. 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. MW. diffusa. 
Lower scale about two-thirds as long as the second; flowering scale with an awn four 
Son 
times its length or more. E 9. WM. microsperma, 
Panicle open, its branches long and spreading. ae 
Culms 114° tall or more; panicle diffuse; leaves elongated, not rigid. 10. M. capillaris. 
Culms 1° tall or less; leaves 2’ long or less, rigid. 
Secondary branches of the panicle single; basal leaves short, numerous, strongly recurved. 
i. MW. gracillima. 
Secondary branches of the panicle fascicled; basal leaves few, not recurved. 
12. M. pungens. 
1. Muhlenbergia sobolifera (Muhl.) Trin. Rock Muhlenbergia. (Fig. 320.) 
Agrostis sobolifera Muhl.; Willd. Enum. 95. 1809. 
Muhlenbergia 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, 14’’—3’’ wide, those 
of the branches 1/—3’ long, about 1’’ wide; panicle 
3/-6’ in length, slender, its branches 3//-1’ long; 
outer scales about %’’ 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 I,, Mant. 1:31. 1767. 
Agrostis filiformis Willd. Enum. 95. _ 1809. 
Muhlenbergia Mexicana 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, 1//-3/’ wide, the branch leaves 
smaller; panicle 2/-6’ long, contracted, its branches 
spike-like, 1/-2’ long, erect or appressed; spikelets 
144’/-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 
western Ontario, south to North Carolina, Tennessee and 
the Indian Territory. Aug.—Sept. 
