ZANNICHELLIACEAE Althenia Petit

CLXXXI. ZANNICHELLIACEAE 4

Submerged, perennial aquatic herbs, with creeping rhizomes. Leaves alternate or subopposite, linear, sheathing at the base. Flowers unisexual, small, solitary or in falcate cymes. Male flowers pedunculate; perianth absent or cupular; stamens 1-3; anthers connate, sessile, opening by longitudinal slits. Female flowers sessile or shortly pedunculate; perianth absent or cupular or of 3 segments; carpels 1-9, free, with 1 ovule; styles simple or

divided into 2 filiform stigmas.

Fruitlets achene- or nut-like; seeds without endosperm.

1 Dioecious, marine; leaves 2-4 mm wide, spinulose-dentate towards the apex; styles divided into 2 filiform stigmas

3. Cymodocea 1 Monoecious, in fresh or brackish water; leaves up to 2 mm wide, entire; styles simple

2 Leaves alternate; sheaths adnate to the leaf-base, long-auriculate; male flowers with a 3-dentate, cupular perianth; female flowers with a perianth of 3 segments 1. Althenia

2 Leavessubopposite(oralternateonnon-floweringbranches);

sheaths free from the leaf-base, stipuliform; male flowers

without a perianth; female flowers with a cupular perianth

2. Zannichellia

1. Althenia Petit 1

Monoecious or dioecious. Stems elongated, slender. Leaves alternate; sheaths auriculate. Flowers axillary, solitary. Male flowers with a 3-dentate, shallowly cupular perianth; stamens 1 -3; anthers 1 - or 2-thecous. Female flowers with a perianth of 3 segments; carpels 3; styles simple.

1. A. filiformis Petit , Ann. Sei. Obs. 1: 452 (1829)

(ind. A. barrandomi Duval-Jouve ).

Monoecious. Leaves less than 0-5 mm wide, setaceous, acute, entire; sheaths long-auriculate. Stamen 1; anther 1 -thecous. Styles elongated, filiform; stigma infundibular. Fruitlets 2-3 mm (excluding the beak), stipitate, ellipsoid or oblong-ellipsoid, smooth, beaked. Brackish water near the sea. S. & W. Europe, from W. France to N. W. Jugoslavia.?Co Ga Hs It Ju?Lu Sa Si.

A record from S.E. Russia requires confirmation.