Zosteraceae Dumort.
Infl. a spadix or spike enclosed, at least at first, in a spathe-like If-sheath. Fls ∞, in 2 vertical rows on one surface of the flattened axis. Per. 0 or perhaps sts represented by a bract-like lobe (retinaculum). Stamen solitary; anthers sessile, dehiscence longitudinal; pollen thread-like. Carpel solitary, narrowing above to short style; stigmas 2, flagelliform; ovule solitary, pend. Achene ± beaked, indehiscent or bursting irregularly. Rhizomatous, glab., marine perennials with flattened stems and 2-ranked, linear, sheathing lvs. Two genera, Zostera monoec., widespread, Phyllospadix dioec., from north Pacific coasts only.
Modern authors mostly treat the fls as simple and unisexual whereas previously each fl. was regarded as bisexual, consisting of a carpel and a stamen attached at the same level.
