The families of flowering plants

L. Watson and M.J. Dallwitz

Cymodoceaceae N. Taylor

~ Zanichelliaceae.

Habit and leaf form. Herbs. Perennial; without conspicuous aggregations of leaves (herbaceous and monopodial, or woody and sympodial); rhizomatous. Hydrophytic; marine; rooted. Leaves submerged. Leaves alternate, or opposite (or apparently so); when alternate, spiral, or distichous; sessile; sheathing. Leaf sheaths with free margins. Leaves simple; epulvinate. Lamina entire; linear, or subulate; parallel-veined. Leaves ligulate (at junction of sheath and blade). Axillary scales present. Leaf development ‘graminaceous’.

Leaf anatomy. The leaf lamina bifacial. Hairs absent. The mesophyll without crystals. Foliar vessels absent.

Axial (stem, wood) anatomy. Secondary thickening absent. The axial xylem without vessels.

Root anatomy. Root xylem without vessels.

Reproductive type, pollination. Plants dioecious. Pollination by water.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes. The ultimate inflorescence units cymose. Flowers small.

Perianth absent.

Androecium in male flowers 2. Androecial members coherent (the two dorsally united, the anthers paired on a common filament). Androecium exclusively of fertile stamens. Stamens 2. Anthers unilocular, or bilocular; tetrasporangiate. Pollen grains lacking exine, and dispersed in the sea as long filaments. Pollen grains nonaperturate; 3-celled.

Gynoecium 2 carpelled; apocarpous; eu-apocarpous; superior. Carpel stylate; apically stigmatic; 1 ovuled. Placentation apical. Ovules pendulous; non-arillate; orthotropous; bitegmic.

Fruit fleshy, or non-fleshy (exocarp hard or fleshy, sometimes enclosed in a fleshy bract); an aggregate. The fruiting carpel indehiscent; nucular. Seeds non-endospermic. Cotyledons 1. Testa without phytomelan.

Physiology, phytochemistry. Proanthocyanidins present.

Geography, cytology. Sub-tropical to tropical. Warm seas. X = 7.

Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Alismatiflorae; Zosterales. APG III core angiosperms; Superorder Lilianae; non-commelinid Monocot. APG IV Order Alismatales.

Species 16. Genera 5; Cymodocea, Amphibolis, Halodule, Syringodium.

Illustrations. • Cymodocea rotundata, as Phucagrostis: Hemprich & Ehrenberg (1820–25). • Cymodocea nodosa, as Phucagrostis major: Cavolini, Ann. Sci. Nat. Bot. (1864). • Halodule uninervis, with Zannichellia palustris: Codd, de Winter & Ryecroft, Flora of Southern Africa 1 (1966). • Le Maout and Decaisne: Phucagrostis major, as Cymodocea.

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 15th April 2018.’.