|
Ischaemum L., Sp. Pl. 2: 1049. 1753.
鴨嘴草屬
Annuals or perennials; culms solid. Leaf-blades lanceolate or linear, sometimes with a pseudo-petiole. Inflorescence composed of 2 to several spike-like racemes, more or less digitately arranged, if only 2 racemes present, then usually very closely appressed, at first sight appearing as a single racme. Spikelets dorsally compressed, 2-flowered, sometimes 1-flowered, in alternate pairs, the one sessile: and the other pedicelled. Pedicelled spikelet falling entire from pedicel, the callus blunt, or usually stipe-like and bearded. All sessile spikelets are placed in front, all pedicelled spikelets behind, sometimes pedicels very short; lower glume oblong or lanceolate, convex, often hardened in lower half, often tuberculate or transversely rugose, often winged towards apex; entire or a 2-lobed, numerous-nerved, the nerves of the hardened lower glume only distinct near top, the margins inrolled or inflexed; upper glume narrower, often longer, boat-shaped, often keeled, acute, muticous or with very short awn; lower lemma shorter than lower glume, ovate-oblong, apex narrowed, thinly membranous; lower palea nearly as long, oblong; stamens 3, or reduced into staminodes; upper lemma well-developed, convex, hyaline, entire or 2-fid and awned from sinus, the awn short or long, the nerves 3-5 upper palea 2-nerved; stamens 3; styles 2, free, the stigmas plumose. Caryopsis oblong.
About 50 species distributed in the tropical and subtropical regions; nine species.
One variety and two forms are found on the plains and littoral regions of Taiwan.
|
KEY TO THE SPECIES and VARIETIES
|
|
|
| 1 |
Lower glume of sessile spikelets transversely rugose. |
|
(2) |
| + |
Lower glume of sessile spikelet not transversely rugose. |
|
(4) |
| |
|
|
|
| 2 (1) |
Lower glume with 2-4 discontinuous ridges; pedicels and rachis-joints not thickened |
|
var. gibbum |
| + |
Lower glume with 4-5 continuous ridges; pedicels and rachis-joints thickened |
|
(3) |
| |
|
|
|
| 3 (2) |
Spikelets about 5.5 mm long; plant body 60-70 cm high |
|
var. segetum |
| + |
Spikelets about 4 mm long; plant body up to 30 cm high |
|
Ischaemum akonense |
| |
|
|
|
| 4 (1) |
Sessile spikelets up to 5 mm long, obovate to oblong; pedicelled spikelets with geniculate awn; culms creeping |
|
Ischaemum indicum |
| + |
Sessile spikelets 6-9 mm long, lanceolate; pedicelled spikelets awnless or with a straight awn.
6. Racemes not exceeding the uppermost sheath; leaves petiolate |
|
(5) |
| |
|
|
|
| 5 (4) |
Racemes not exceeding the uppermost sheath; leaves petiolate |
|
Ischaemum muticum |
| + |
Racemes far exceeding the uppermost sheath; leaves not petiolate. |
|
(6) |
| |
|
|
|
| 6 (5) |
Lower glume of sessile spikelets flattened and nerved at upper part , coriaceous below middle; if awned, column of awn not exceeding the spikelet. |
|
(7) |
| + |
Lower glume of sessile spikelets, flat, slightly coriaceous at base; internode of rachis yellow, villous; column of awn far exceeding spikelet |
|
(9) |
| |
|
|
|
| 7 (6) |
Sessile spikelets bearing a geniculate awn; lower glume lanceolate, narrowly winged |
|
Ischaemum crassipes |
| + |
Sessile spikelets awnless or straight awned; lower glume broadly elliptic, broadly winged. |
|
(8) |
| |
|
|
|
| 8 (7) |
Lower glume of sessile spikelet, peduncle and sheaths not villous |
|
Ischaemum crassipes |
| + |
Lower glume of sessile spikelet pilose; peduncle and sheaths villous |
|
Ischaemum aristatum |
| |
|
|
|
| 9 (6) |
Lower glume of sessile spikelets keeled but wingless, narrow; ligule truncate |
|
var. aristatum |
| + |
Lower glume of sessile spikelets keeled and winged, broadly lanceolate; ligule
tongue-like |
|
Ischaemum setaceum |
|
|
|
List of lower taxa
| Related Links (opens in a new window) |
|
Treatments in Other Floras @ www.efloras.org
Other Databases
|
|
|
|
|
|
|
