Northern Prairie Wildlife Research Center
Aquatic and Wetland Vascular Plants of the Northern Great Plains
56. Ruppiaceae, The Ditch-grass Family
1. Ruppia L. -- Ditch-grass, widgeon-grass
1. Ruppia maritima L.
Perennial submersed aquatic; stems slender and terete, flexuous, anchored
by roots, branching at the base and short-branched above, to 6 dm long, the
internodes often zigzag. Leaves simple, alternate, sessile, the blades
filiform, attenuate, mostly 5-15(25) cm long, ca. 0.5 mm wide, stipular-sheathing
at the base. Inflorescence a reduced axillary spike, included in the
leaf sheath at anthesis; peduncles elongating and usually coiling as
fruits develop. Flowers 2 per spike, perfect; perianth none or
minute; stamens 2, briefly adherent during peduncle elongation; carpels
6 or more, separate, stipitate, the stipes gradually elongating from the common
base so that the fruits are borne in an umbel. Fruits olive-green to
black, ovoid, symmetrical to asymmetrical, beaked, 1.5-3 mm long. Jul--Aug.
Alkaline to saline waters of lakes, ponds and marshes; locally common and scattered
throughout the region; (Coastal marshes from N.Amer. to S.Amer. and in the Old
World, also inland throughout Can. and the U.S., primarily in brackish or saline
waters).
Two fairly distinct forms can be recognized in the region. The prevalent
form is var. occidentalis (Wats.) Graebn., a robust, strongly rhizomatous
plant with leaf sheaths 1.5-3 cm long. This variety often forms extensive
grasslike mats in alkaline waters. A smaller form of lesser occurrence most
closely fits var. rostrata Agardh., with leaf sheaths to 1 cm
long. This form seems to favor waters of more extreme salinity.
Return to Family -- Ruppiaceae - The Ditch-grass
Family
U.S. Department of the Interior |
U.S. Geological Survey
