This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Marine plants with slender rootstocks and branching compressed stems. Leaves 2-ranked, sheathing at the base, the sheaths with inrlexed margins. Spadix linear, contained in a spathe. Flowers monoecious, arranged alternately in 2 rows on the spadix. Staminate flower merely an anther attached to the spadix near its apex, 1-celled, opening irregularly on the ventral side; pollen thread-like. Pistillate flower fixed on its back near the middle; ovary 1; style elongated; stigmas 2, capillary; mature carpels flask-shaped, membranous, rupturing irregularly beaked; seeds ribbed; embryo ellipsoid. [Greek, referring to the ribbon-like leaves.]
About 6 species of marine distribution, the following the type of the genus.
Zostera marina L. Sp. PI. 968. 1753.
Leaves ribbon-like, obtuse at the apex, 1°-6° long, 1 "-4" wide, with 3-7 principal nerves. Spadix 1'-3 1/2 long; flowers about 3" long, crowded, usually from 10-20 of each kind on the spadix; ovary somewhat vermiform; at anthesis the stigmas are thrust through the opening of the spathe and drop off before the anthers of the same spadix open; the anthers at anthesis work themselves out of the spathe and discharge the glutinous stringy pollen into the water; seeds cylindric, strongly about 20-ribbed, about 1 1/2" long and \" in diameter, truncate at both ends, the ribs showing very clearly on the pericarp.
In bays, streams and ditches along the Atlantic Coast from Greenland to Florida and on the Pacific from Alaska to California. Also on the coasts of Europe and Asia. Called also Wrack or Widgeon-grass; Sea, Sweet, Barnacle and Turtle-grass, Grass-weed, Tiresome-weed, Bell-ware, Drew. Summer.