1. Inflorescences composed of a single spikelet; leaf blades 0.5-1.5 cm long, stiff ..... D. littoralis
Plants rhizomatous and sometimes stoloniferous. Culms
10-60 cm, usually erect, sometimes decumbent or prostrate. Blades of upper
leaves 1-8(20) cm, rigid and divaricate to lax and ascending, usually equaling
or exceeding the pistillate panicles, varying with respect to the staminate
panicles. Pistillate panicles 1-7 cm, often congested, with 2-20 spikelets.
Pistillate spikelets 5-20 mm long, 4-7 mm wide, with 5-20 florets; lower
glumes 2-3 mm; upper glumes 3-4 mm; lemmas 3.5-6 mm; paleas
with serrate keels. Caryopses 2-5 mm, tapered or truncate. Staminate
panicles and spikelets similar to the pistillate panicles and spikelets,
but the lemmas somewhat thinner in texture and the paleas not bowed-out. Anthers
3-4 mm. 2n = 40.
Distichlis spicata grows in saline soils of the Western Hemisphere and
Australia. Numerous infraspecific taxa have been recognized in the past, but
none appears to be justified. Recent North American accounts of Distichlis
have usually recognized plants from maritime coasts as distinct from those
growing inland, supposedly having more congested inflorescences, but the range
of variation is similar in the two habitats.
López Soto et al. (2009) examined the leaf anatomy of six species and 11 varieties of Distichlis. They found that D. australis and D. palmeri differed from all other species and that D. humilis, D. spicata, and D. scoparia were anatomically similar but distinguishable. They found no characters or character combinations that supported recognition of infraspecific taxa within D. spicata. Harrington et al. (2009), on the other hand, found that inland plants, which Rydberg called D. stricta, differed from coastal plants in molecularly, cytogenetically, and in their phenology. On that basis, it seems that treatment of the inland plants as D. spicata subsp. stricta (Torr.) Thorne is warranted. The reason for no treating them as species is pragmatic, the lack of morphological characters for distinguishing them.
Plants with long, wiry stolons. Culms 8-15 cm, clustered, erect, with numerous short, leafy, lateral branches. Leaves clustered on distant to closely-spaced, short, lateral shoots; sheaths 4-6 mm, rounded, smooth, shiny, glabrous or puberulent at the base; ligules thickly membranous ciliate rims; blades 0.5-1.5 cm long, 1-2(3) mm wide, stiff, subulate, uniformly many-veined. Inflorescences terminal, composed of a single glabrous spikelet, this enclosed, and almost concealed, by the uppermost leaf sheaths. Pistillate spikelets subterete, with 3-5 florets, distal florets rudimentary; disarticulation tardy, below the lowest floret; glumes absent; lemmas coriaceous, glabrous, 9-veined, acute; paleas coriaceous, keels prominently winged, wings overlapping and enclosing the caryopses. Staminate spikelets similar to the pistillate spikelets, but smaller and the glumes and lemmas thinner. x = 10. Name from the Greek monos, single, anthos, flower, and chloë, grass, alluding to the solitary spikelets. 2n = 40.
Distichlis littoralis grows in moist, sandy, saline soils along the coast of southern California and the southeastern United States, northeastern Mexico, and the Caribbean islands. It was previously placed in Monanthochloë but Bell and Columbus (2008) demonstrated that Monanthochloë is nested within Distichlis.
Colonial from hard, white rhizomes with stiff scales; stems 1.5-4 dm, with numerous rigid, involute lf-blades 5-10 cm, the lvs often pilose at the collar; infl congested, short, to 8 cm; lemmas ovate or lance-ovate, about equaling the palea, this with 2 winged keels, the wings ciliolate and/or irregularly serrate; 2n=40. Two vars.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.