This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Muhlenbergia ambigua Torr. Nicollet's Rep. 164. 1843.
Glabrous, culms 1° tall or lower, erect, branched, smooth. Sheaths shorter than the internodes; ligule about 1/2" long erose-truncate; blades 1-3' long, \"-2" wide, scabrous; panicle 1-3' long, rigid, its branches 1/2'-1' long, dense, ap-pressed; outer scales of the spikelet awn-pointed, unequal, the longer about 2" in length and exceeding the body of the third scale which is scabrous, villous, and attenuate into an awn 2-3 times its length; a fourth narrow awned scale is nearly always present.
Along a lake shore in Minnesota.
Culms 1°-2 1/2° tall, erect, slender, smooth and glabrous-Sheaths shorter than the internodes, smooth or slightly scabrous; ligule about 1/2" long, truncate, naked or minutely ciliate; blade:; 2 1/2-5' long, l"-2" wide, erect, flat, rough; panicle often tinged with purple, 2-4' in length, dense, branches 1/2'-1 1/2' long, erect; outer scales of the spikelet equal, or the second a little the longer, smooth, scabrous on the keel; third scale shorter, smooth and glabrous, bearing an awn 2-3 times its length, the basal hairs silky, erect, fully as; long as the scale.
A smooth and glabrous annual. Culms slender, up to 1° tall, but usually 1/2 that height; ligule about 1" long, acute; blades, erect, up to 2' long, i" wide, flat, involute; panicle slender, sometimes interrupted below, 1'-2 1/2' long, the slender branches appressed; spikelets, exclusive of the short awn when present, a little over 1" long, the outer scales less than i as long as the spikelet, rounded or truncate at the erose apex, the flowering scale very acute and often with a short point or awn.
In meadows and along brooks, Montana to Nebraska and Colorado. Aug. and Sept.
Agrostis brevifolia Nutt. Gen. 1: 44. 1818.
Sporobolus Richardsonis Merrill, Rhodora, 4: 46. 1902.
Sporobolus brevifolius Scribn. Mem. Torr. Club, 5: 39. 1895.
Smooth and glabrous, culms 6'-18' tall, arising from a horizontal rootstock, erect, slender, decumbent and branching above. Sheaths much shorter than the internodes; ligule 3/4"-1" long, acutish; blades 1/2'-2' long, involute-setaceous; panicle 1/2-3' in length, usually about 1 1/2', linear, its branches 1/4'-1/2' long, erect orappressed; spikelets 1 1/4"-1 1/2" long, the outer scales unequal, about one-half as long as the third, scabrous on the* keel and at the apex; third scale long-acuminate, sometimes cuspidate, scabrous toward the apex.
In meadows and along rivers, Anticosti Island and Maine to British Columbia, south in the mountains to New Mexico and California. Summer.