Marsh Foxtail, Knee-jointed Foxtail, Floating Foxtail
Introduced perennial grass 10-60cm tall, sometimes creeping. Leaves with a sheath at the base. Ligule a membrane without a fringe of hairs. Leaves flat, 2-12cm long, 1-8mm wide, hairless to rough. Spikelets green, brown, or purplish, 2-4mm long. Mature seed heads cylindrical. Seeds with one awn.
Description and photo in G.M. Cunningham, WE Mulham, PL Milthorpe and J H Leigh (1981 and later printings) Plants of Western New South Wales page 53
ausgrass2 description: http://ausgrass2.myspecies.info/content/alopecurus-geniculatus