| Christmas Island Duck Beak | |
|---|---|
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Monocots |
| (unranked): | Commelinids |
| Order: | Poales |
| Family: | Poaceae |
| Genus: | Ischaemum |
| Species: | I. nativitatis |
| Binomial name | |
| Ischaemum nativitatis Jansen ex Renvoize |
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Ischaemum nativitatis, commonly known as the Christmas Island Duck Beak, is a tropical grass in the Poaceae family. It is endemic to Christmas Island, an Australian territory in the north-eastern Indian Ocean. The specific epithet comes from the Latin nativitas (birth) referring to the birth of Christ, or Christmas, after the name of the island.[1]
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The Christmas Island Duck Beak is an erect, tufted grass, 250–700 mm tall, with the stems often branched and the nodes smooth. The leaves are 30–110 mm long, 2.5–7 mm wide and are scattered along the stem. The two bristly racemes are 15–50 mm long, with long and hairy pedicels and rachis, and with paired, [Sessility (botany)|[sessile]] spikelets 4.5 mm long and distinctly awned. The glumes are leathery at the base; the lower, bidentate glume has two membranous wings in the apical half; the upper glume has a winged keel towards the apex and a 6 mm awn. The flowers have glassy lemma and leathery palea about 3.5 mm long, with the awn of the upper lemma 15 mm long and twisted at the base.[1]
Found only on Christmas Island, the grass occurs sporadically along the northern and western coasts, on exposed limestone pinnacles behind the sea cliffs, in pockets of coralline sand, and in front of dense stands of Scaevola taccada and Pandanus nativitatis.[1]
The grass was first recorded, though not properly described, by Charles William Andrews and Henry Nicholas Ridley as I. foliosum var. leiophyllum Hack. ex Rendle, a variety endemic to Christmas Island. Otto Stapf later determined that the Christmas Island specimens represented a distinct species, I. nativitatis Stapf, but again failed to publish the name validly. In 1953 P. Jansen tried to validate the name by publishing a full description, but omitted the required Latin diagnosis, leaving the name still invalid under the International Code of Botanical Nomenclature. Eventually, in 1985, S. A. Renvoize validated the name I. nativitatis by publishing a full Latin description.[1]
The grass is closely related to I. foliosum Hack. from New Caledonia and Vanuatu, which it resembles in appearance.[1]