Zostera. | LXXVIIL NAIADEZ, 423 
I, ZOSTERA. ZOSTERA. 
Marine herbs, the stem creeping and rooting in the sand or mud, with 
long, grass-like, alternate leaves. Flowers enclosed in a sheath near the 
base of leaves similar to the others, but usually smaller. Within this 
sheath is an oblong or linear, thin, leaf-like peduncle, on one side of which 
are arranged in two rows a few sessile anthers, with 3 or 4 sessile or nearly 
sessile ovaries, tapering into a deeply 2-cleft, linear style. Embryo split 
longitudinally, with a deep groove forming 2 valves, which fold over the 
long, curved, linear cotyledonar end. 
A genus hitherto limited to the two British species. 
Leaves seldom a, foot long. Ripe seeds smooth . : 3 : . 2, Z. nana. 
Leaves usually more than a foot long. Ripe seeds furrowed . . Ll. Z. marina. 
1, Z. marina, Linn. (fig. 949). Common Zostera, Grass-wrack.— 
Creeping stems or rootstocks often very long and rather fleshy. Leaves 
varying from near a foot to several feet in length, and from 2 to 3 or 4 lines 
in breadth, with 3, 5, or even 7 more or less distinct parallel nerves. 
Flowering sheath near the base of the floral leaves, from 1 to 14 or near 2 
inches long. The fiattened peduncle narrow-linear, and said to be always 
without the horizontal appendages of Z. nana. Seeds oblong, marked by 
longitudinal furrows. 
Common near the sandy or muddy edges of the sea, in temperate regions of 
the world, usually at or below low-water mark, and often thrown up in great 
quantities by the tide. Abundant round the British Isles. Fl. summer, 
or, according to some, in spring only. 
2, Z nana, Roth. (fig. 950). Dwarf Zostera,—Closely resembles the 
smaller forms of Z. marina, of which itis believed by some to be a mere 
variety. ‘The leaves are usually from a few inches to near a foot long, very 
narrow, with only 1 or rarely 3 distinct nerves ; the flowering sheath about 
half an inch long, and the flattened peduncle inside has to every ovary a 
little transverse appendage or band. Seeds shorter than in Z. marina, per- 
fectly smooth. 
On sandy shores, usually between high- and low-water marks, in various 
parts of the world. Common in western Europe, and has been found on 
several points of the British coasts. Jl. summer and autumn. The seeds 
appear certainly distinct in the two species; the constancy of the other 
characters is doubtful. I have examined only the dwarf species in a living 
flowering state. 
Il. NATAS. NAIAD. 
Slender, branching, submerged plants, with linear, opposite or ternate, 
entire or toothed leaves, often crowded into whorls: or clusters. Flowers 
small and sessile, often clustered with the branch-leaves in the axils, and 
dicecious or rarely monoecious; the males consisting of a single, nearly 
sessile anther, enclosed in two bracts; the females of a single ovary, sessile 
in the sheathing base of the leaf, with 2 to 4 subulate stigmas. Fruita 
small, seed-like drupe. Embryo straight. 
A genus of few species, widely spread over a great part of the globe. 
1, NW. flexilis, Rostk. (fig. 951). Slender Naiad.—Leaves narrow- 
