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..
Grasses varying greatly in habit and inflorescence. Leaf-blades narrow, often involute-setaceous. Spikelets narrow, 1-flowered. Scales 3, narrow, the two outer carinate; the third rigid and convolute, bearing three awns occasionally united at the base, the lateral awns rarely wanting or reduced to rudiments. Palet 2-nerved. Stamens 3. Styles distinct. Stigmas plumose. Grain free, tightly enclosed in the scale. [Latin, from arista, an awn.]
Awns not articulated to the scale.
Central awn coiled at the base.
First scale usually equalling or sometimes slightly shorter than the second scale, which is
commonly 3 1/2"-4 1/2" long.
First scale much shorter than the second (often but little more than l/2 as long), which is 5"-8" long.
Lateral awns short, straight and erect, 1/2"-1" long, the central awn usually more than
five times their length, its straight portion 2l/2"-4" long.
Lateral awns more or less spreading, usually a little spiral at the base, the central awn
from 1/2 again to twice their lenth, its straight portion s"-8" long.
Central awn not coiled of the base.
Panicle narrow, linear to oblong, branches short (or long in no. 13), erect or ascending.
Central awns and sometimes the lateral ones also stronlgy reflexed, the bend semicircular.
Central awn from erect to spreading with no such bend at the base.
First scale much shorter than the second, usually about 1/2 as long.
Spikelets crowded, 4 - 6 on the short branches, which are spikelet-bearing to the
base or nearly so.
Spikelets not crowded, usually 1-3 on branches naked at the base.
Second scale of spikelet 8" long or less, equalling or exceeding flowering scale.
Panicle simple or nearly so, its branches bearing 1 spikelet; culms com-
monly naked above.
Panicle compound, its branches bearing 2 or more spikelets; culms usually
Second scale of the spikelet 10" long or more, 1 1/2-2 times as long as the
First scale from a little shorter than to exceeding the second.
Spikelets exceeding 10" long; first scale 5-7-nerved.
Spikelets less than 8" long; first scale 1-3-nerved.
Leaf-sheaths glabrous or sparsely pubescent.
First scale generally shorter than or equalling the second.
Flowering scale 2l/2"-2" long, its central awn usually 3"-5" long.
Flowering scale 3 1/2"-4 1/2" long, its central awn exceeding in length.
First scale exceeding the second.
Leaf-sheaths, at least the lower ones, densely wooly.
Panicle diffuse and open, the branches very long and widely spreading.
Awns articulated to the scale, united at the base into a spiral column.
Column conspicuous, 3" long or more.
Column inconspicuous, 1" long or less.