ZOSTERACEAE

EEL-GRASS FAMILY

Robert F. Thorne

Perennial, glabrous, submersed marine aquatic, rhizomed, monoecious or dioecious
Stem flat, leafy, creeping or short with wide, thick base
Leaves alternate, 2-ranked or tufted; sheath open or closed; ligule present; blade long, linear, ribbon-like, tip entire to notched
Inflorescence: spike, axillary, flattened, enclosed by membranous, leaf-like bract; flowers many, 2-rowed on 1 side of axis, each enclosed by translucent, scale-like bractlets or not
Staminate flower: perianth 0; stamen 1, anther 2-chambered; pollen thread-like, < 2 mm
Pistillate flower: perianth 0; ovary 1, chamber 1, ovule 1, style 1, stigmas 2
Fruit: drupe or nutlet
Genera in family: 3 genera, ± 18 species: seacoasts, worldwide except tropical; some species source of food for marine animals, some aboriginal humans.

ZOSTERA

EEL-GRASS

Monoecious; rhizomes creeping, slender
Stem < 300 cm, leafy
Leaves 30–150 cm, alternate, cauline; blade with 3–7 parallel veins
Inflorescence enclosed by sheath of subtending leaf; staminate flowers alternating with pistillate flowers
Staminate flower: anther sessile
Pistillate flower: ovary tapered to short style
Fruit: nutlet, flask-like, wall translucent
Seed ± 3 mm, 1 mm diam, ± 20-ribbed or smooth, base truncate
Species in genus: 12 species: temp to cold marine waters worldwide
Etymology: (Greek: from ribbon-like leaves)
Reference: [Phillips & Echeverria 1990 Pacific Science 44:130–134]
Important food source for marine animals, some aboriginal humans.

Native

Z. pacifica S. Watson

Leaf 12–18.5 mm wide; tip generally notched
Seed: surface smooth or faintly ridged
Ecology: Common. Subtidal waters
Elevation: 5–17 m below mean low tide.
Bioregional distribution: North Coast, Central Coast, South Coast
Distribution outside California: to British Columbia
Synonyms: Z. asiatica Miki