6. ZOSTERA, Linn.
Marine submerged plants. Rhizomes slender, branched, creeping and rooting at the nodes, often matted. Stems short, slender, leafy, compressed. Leaves distichous, alternate, narrow-linear, grass-like, 1–5-nerved, sheathing at the base; sheaths stipuliform, with inflexed margins. Flowers monœcious, the males and females placed alternately upon one face of a narrow spadix enclosed within the dilated membranous base of a leaf. Perianth wanting. Male flowers: Anther solitary, sessile, oblong, cylindric, curved, 1-celled, dehiscence longitudinal; pollen confervoid. Female flowers: Carpel solitary, laterally attached above the middle, narrowed into a short subulate style; stigmas 2, capillary; ovule pendulous from the apex of the cell. Eipe carpel oblong, membranous, bursting irregularly. Seed pendulous; testa membranous, often striated; embryo large, deeply grooved, the linear incurved cotyledonary end sunk in the groove.
Three or four closely allied species are known, found in shallow water on the shores of most temperate regions.
| Leaves 3-9 in. × 116–110 truncate or notched at the tip. Spadix with transverse appendages, one folded over each carpel | 1. Z. nana. |
| Leaves 9–18 in. × 110–16 in., rounded at the tip | 2. Z. tasmanica. |
1. Z. nana, Roth, Enum. Pl. Phæn. Germ. i. 8.—Rhizomes slender, matted. Leaves 3–9 in. long, rarely more, 116–110 in. broad, narrow-linear, truncate or obscurely notched at the tip, with 3–5 faint parallel nerves on each side of the stout midrib and distant transverse veinlets, margins thickened. Floral sheaths or spathes ½–1 in. long, on peduncles of equal length, the blade of the leaf continued above the sheath, the sheath itself much wider than the blade. Spadix 6–12-flowered, its margins with transverse membranous appendages folded inwards, one over each carpel. Stigmas usually protruding through the slit of the spathe. Fruit about 110 in. long, oblong, obscurely striate.—Benth. Fl. Austral. vii. 176; Kirk in Article 54#392|Trans. N.Z. Inst. x. (1878) 392. Z. Muelleri, Irmisch ex Aschers. in Linnæa, xxxv. (1867–68) 168.]]
North and South Islands, Stewart Island: Muddy and sandy shores throughout, usually between high- and low-water marks. Widely distributed in temperate seas.
2. L. tasmanica, Martens ex Aschers. in Linnæa, xxxv. (1867–68) 168 (?).—Rhizomes slender, wide-creeping. Leaves 9–18 in. long, 110–16 in, broad, narrow-linear, rounded at the tip, not truncate, with 1–3 stout nerves on each side of the midrib and several finer ones between, cross-veinlets distant. Flowers and fruit not seen.—Z. marina, Hook. f. Handb. N.Z. Fl. 742 (not of Linn.).
North and South Islands: Not uncommon in sandy or muddy places along the coasts, often in water of considerable depth.
