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..
Mostly tufted perennial grasses, with flat or convolute leaf-blades and paniculate inflorescence. Spikelets 2-several-flowered. Two lower scales empty, more or less unequal, acute, keeled; flowering scales membranous, narrow, rounded on the back, 5-nerved, usually acute, and generally awned at the apex. Palet scarcely shorter than the scale. Stamens 1-3. Styles very short, distinct. Stigmas plumose. Grain glabrous, elongated, often adherent to the scale or palet. [Latin, stalk or straw.]
Spikelets perfect; stigma-branches toothed, bilateral.
Empty scales membranous, green, narrow, the second one 3-5-nerved.
Leaf-blades involute or folded, 1" wide or less.
Annuals; stamens 1 or 2.
Awn not longer than flowering scale; spikelets 5-many-flowered.
Awn more than twice as long as flowering scale; spikelets 2-5-flowered.
First empty scale half as long as the second or less.
First empty scale more than half as long as the second.
Perennials; stamens 3.
Innovations extravaginal; plants with rootstocks or stolons.
Innovations intravaginal; plants densely tufted, no rootstocks or stolons.
Awns more than half as long as membranous flowering scales.
Awns less than one-half as long as the coriaceous flowering scales.
Flowering scales short-awned; leaf-blades setaceous.
Culms 8' tall or more; culm blades long.
Culms 6' long or less; culm blades short.
Flowering scales awnless; leaf-blades capillary.
Leaf-blades flat, 2" wide or more.
Flowering scales awnless or short-awned.
Flowering scales 2 1/2"-3 1/2" long, spikelets 5-10-flowered.
Flowering scales 2" long or less, spikelets 3-6-flowered.
Spikelets very broad; panicle branches spikelet-bearing from middle or below.
Spikelets lanceolate; branches elongated, spikelets at the end.
Flowering scales with an awn twice their length or more.
Empty scales broad, scarious, with broad hyaline margins, thin, 1-nerved; base of the culm
clothed with dry leafless sheaths.
Spikelets unisexual; stigma-branches arising from all sides; dioecious.
F. con finis.