Amphibromus fluitans, n. s.
Culms floating or procumbent, glabrous, 12″–18″ long, rooting at the nodes, leafy; leaves slightly scabrid, flat, ligule laciniate. Panicle 1″–2″ long, partially included in the loose sheath, simple, or with one or two short distant branches, lax, rhachis and pedicels scabrid, slender; spikelets
pedicellate 5–7 flowered, faintly pubescent; outer glumes unequal, one-third the length of the spikelets; flowering glume more than twice as long as the outer glume, 5-nerved, bifid, awn dorsal springing from near the base of the glume, free at its apex, scabrid, not twisted, palea equalling the flowering glume, with 2 stout ciliated nerves, truncate, the apex and upper margins ciliated; caryopsis free.
Hab. North Island: in shallow waters, margins of the Waihi Lake and Creek.
Stamens 3, lodicules narrow, acute; stigmas 2, minute, ovary loosely invested by the palea. Flowering glume with a few short hairs at the base. Pedicels varying from ¼″–1½″ in length: occasionally two or more pedicels spring from the same point, but in cases of this kind one pedicel is greatly abbreviated.
Our plant is readily distinguished from all other indigenous grasses by its fluitant habit; although in very shallow water it is suberect, yet as a general rule little more than the panicle is elevated above the water. Owing to the rhachis of the spikelet being articulated below each flower, the glumes fall away almost immediately after the extrusion of the panicle from the sheath, leaving only the naked pedicels, so that there is but little to attract attention to the plant, which may easily be passed unnoticed.
Amphibromus fluitans is usually if not invariably cleistogamous, fertilization being effected before the panicle is extruded: in fact extrusion is often delayed until the grain is nearly matured. I suspect that the stamens are not always developed in the uppermost flowers of each spikelet, but the flowers must be collected in an earlier state, before this point can be positively determined.
Our plant differs from the Australian species A. neesii, Steudel, in the procumbent habit, shorter leaves, smaller panicle, and straight awn. A. neesii is found in all the Australian Colonies except Queensland, and attains its greatest luxuriance in moist situations.