6. ZOSTÈRA, L. Grass-wrack. Eel-grass.
Flowers monœcious; the two kinds naked and sessile and alternately arranged in two rows on the midrib of one side of a linear leaf-like spadix, which is hidden in a long and sheath-like base of a leaf (spathe); the sterile flowers consisting of single ovate or oval 1-celled sessile anthers, as large as the ovaries, and containing a tuft of threads in place of ordinary pollen; the fertile of single ovate-oblong ovaries attached near their apex, tapering upward into an awl-shaped style, and containing a pendulous orthotropous ovule; stigmas 2, long and bristle-form, deciduous. Utricle bursting irregularly, enclosing an oblong longitudinally ribbed seed (or nutlet). Embryo short and thick (proper cotyledon almost obsolete), with an open chink or cleft its whole length, from which protrudes a doubly curved slender plumule.—Grass-like marine herbs, growing wholly under water, from a jointed creeping stem or rootstock, sheathed by the bases of the very long and linear, obtuse, entire, grass-like, ribbon-shaped leaves (whence the name, from ζωστήρ, a band).
1. Z. marìna, L. Leaves obscurely 3–5-nerved.—Common in shoal water of bays along the coast, from Newf. to Fla. (Eu.)
7. NÀIAS, L. Naiad.
Flowers diœcious or monœcious, axillary, solitary and sessile; the sterile consisting of a single stamen enclosed in a little membranous spathe; anther at first nearly sessile, the filament at length elongated. Fertile flowers consisting of a single ovary tapering into a short style; stigmas 2–4, awl-shaped; ovule erect, anatropous. Fruit a little seed-like nutlet, enclosed in a loose and separable membranous epicarp. Embryo straight, the radicular end downward.—Slender branching herbs, growing under water, with opposite and linear leaves, somewhat crowded into whorls, spinulose-toothed, sessile and dilated at base. Flowers very small, solitary, but often clustered with the branch-leaves in the axils; in summer. (Ναιάς, a water-nymph.)
1. N. marìna, L. Stem rather stout and often armed with broad prickles; leaves broadly linear (3–18´´ long), coarsely and sharply toothed, the dilated base entire; fruit 2–2½´´ long; seed very finely lineate, oblong, slightly compressed. (N. major, All.)—Marshes and salt-springs of western N. Y. and Mich. Teeth of one or more brownish cells upon a many-celled base. (Eu.)
Var. grácilis, Morong. Internodes long (1–3´) and nearly naked, with only a few teeth above; leaves very narrow, the dilated base also toothed; fruit smaller.—Canoga marshes, western N. Y.; also in Fla.
Var. recurvàta, Dudley. Stems short, inclined to be dichotomously branched, recurved-spreading; leaves usually recurved, the teeth prominent, the dilated base with a projecting tooth each side.—Cayuga marshes, N. Y.
2. N. fléxilis, Rostk. & Schmidt. Stems usually very slender; leaves very narrowly linear (½–1´ long), very minutely serrulate; fruit 1½´´ long, narrowly oblong; seeds lance-oval, smooth and shining.—Ponds and slow streams, N. Scotia to S. C., Iowa and Minn. Teeth on the margins of the leaves 1-celled. (Eu.)—Var. robústa, Morong. Stem stout, few-leaved, sparsely branching, elongated; leaves flat, abruptly acute.—E. Mass., Mich., and Tex.
3. N. Índica, Cham., var. gracíllima, A. Br. Branches alternate; leaves very narrowly linear, nearly capillary, straight, serrate, the rounded lobes of the sheathing base spinulose-ciliate; fruit linear, impressed-dotted between the numerous ribs.—Mass. to Penn., west to Ind. and Mo. Teeth of 3 cells each.