rhachis

Perigynium much as in the Montanæ; spike one, staminate above; pistillate flowers few, often remote, usually on a more or less zigzag rhachis; scales prolonged and leaf-like.—Sp.

Spikelets of a single perfect or unisexual or rudimentary flower, in jointed spikes, in pairs at each joint, mostly imbedded in the thick rhachis.

One spikelet of each pair sterile and shortly pedicelled, the other fertile, sessile and sunk in the rhachis.

Spikelets 4–8-flowered, glabrous or nearly so; glumes 3–7-nerved; rhachis glabrous, but rough on the edges; awns when present straight; leaves flat and often roughish or pubescent above.

Fronds triangular-ovate, 1–3´ long, 3–4-pinnate; rhachis and branches straight, black and shining; ultimate pinnules scarcely a line long, white and powdery on the lower surface.—Clefts of calcareous rocks, Mo., Kan., and southwestward.