Plants annual. Culms 0.5-1(2) m, weak, often decumbent and rooting
at the lower nodes; nodes hispid. Leaves cauline; sheaths
usually shorter than the internodes; ligules 0.4-3.5 mm, ciliate; lower
blades 1-7.5 cm long, 4-20 mm wide, cordate-clasping, ovate to ovate-lanceolate,
flat, margins ciliate (sometimes sparingly so), surfaces usually glabrous, abaxial
surface rarely hispidulous; upper blades greatly reduced. Panicles
1.3-7 cm, flabellate or contracted, with 12-20 rames; rames 1-6(11) cm.
Sessile spikelets: glumes 3-5.5 mm, lanceolate; lower glumes
several-veined; upper glumes 1- or 3-veined; awns 0.3-9 mm, included
or exserted, usually twisted below, sometimes geniculate at midlength; anthers
usually 2, 0.5-0.7 mm. Pedicels absent or to 2 mm. Pedicellate spikelets
absent. 2n = 36.
Arthraxon hispidus is native to Asia, but is naturalized and spreading
along roadsides, shores, ditches and in low woods and fields of the eastern
United States. It is also naturalized in Mexico, Central America, and
the West Indies. Plants in the Flora region belong to A. hispidus (Thunb.)
Makino var. hispidus, the most widespread and variable of the four
varieties.
Arthraxon castratus (Griff.) V. Naray. ex Bor, reported from
Puerto Rico, differs from A. hispidus in having pilose lemma margins,
a palea in its second floret, and three anthers.
Slender, lax, decumbent annual to 5(-10) dm; blades 2-7 cm נ5-15 mm; spikes few-several, digitate, 2-8 cm; normal spikelet (2-)3-5(-8) mm, the lower glume 4-15-veined and with the veins usually spiculate-scabrous at least distally, the upper inconspicuously 3- or 5-veined; sterile lemma virtually veinless, the fertile one 1-veined, often with a supra-basal awn to 10 mm; anthers usually 2; sterile spikelet reduced to the 1-4 mm pedicel, or obsolete; 2n=10. A weed of moist or wet soil, native to se. Asia, now widely intr. in warm regions, and found here and there in our range, n. as far as Mo. and s. N.Y.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
