20. Ischæmum, L.
The grasses of this genus are either annuals or perennials. The inflorescence consists of spikes, solitary, digitate or fascicled, articulate and fragile; the joints of the floral axis and the pedicels of the pedicelled spikelets are trigonous and hollowed ventrally. Spikelets are binate, one sessile and one pedicelled; the pedicelled spikelets are dissimilar from the sessile and both usually 2-flowered. The sessile spikelets have four glumes. The first glume is coriaceous, oblong or lanceolate, convex more or less, marginally winged above the middle, truncate or two-cuspidate at the apex and awnless. The second glume is as long as the first, coriaceous, concave, acute or obtuse, awned or not. The third glume is hyaline, deeply cleft into two lobes with an awn in the cleft, and 3-nerved, paleate; palea is linear-lanceolate enclosing either stamens and ovary or ovary alone. Lodicules are cuneate or quadrate.
KEY TO SPECIES.
- Racemes two or three; the first glume of the sessile spikelet dorsally flat, not channelled or depressed along the middle line.
- Margin of the first glume of the sessile spikelet incurved narrowly from the base to the apex.
- First glume of sessile spikelets with nodulose margins. 1. I. aristatum.
- First glume of sessile spikelets closely transversely ribbed. 2. I. rugosum.
- First glume of the sessile spikelet translucent, bicuspidate at the tip and with smooth margins. 3. I. pilosum.
- Margin of the first glume of the sessile spikelet broadly incurved from below the middle.
- First glume of the sessile spikelet with smooth margins, callus bearded. 4. I. ciliare.
- Margin of the first glume of the sessile spikelet incurved narrowly from the base to the apex.
- Raceme solitary; the first glume of the sessile spikelet deeply grooved at the back along the middle line. 5. I. laxum.
Ischæmum aristatum, L.
This is a perennial grass, with fairly stout, erect or somewhat decumbent, simple or branched, glabrous, leafy stems, 1 to 4 feet high.
The leaf-sheath is loose, glabrous and auricled. The ligule is a distinct membrane, broad or narrow. Nodes are glabrous.
The leaf-blade is linear-lanceolate, flat, acuminate, narrowed towards the base which may be acute, subcordate or rarely even petiolate, glabrous or sparsely hairy above and glaucous beneath, 4 to 10 inches long and 1/4 to 1 inch broad.
The inflorescence consists of one or two, erect, stout or slender, fragile racemes, 1 to 5 inches long.