Plants perennial, of marine waters. Rhizomes present; leaf-bearing branches arising from rhizomes at distances of several internodes; stolons absent. Erect stems rooted in substrate, unbranched, short. Leaves 2–6, basal, submersed, sessile; blade linear, base tapering to stem; apex obtuse; midvein without lacunae along side(s), blade uniform in color throughout; abaxial surfacely without prickles; intravaginal scales entire. Inflorescences 1-flowered to cymose, pedunculate; spathes not winged. Flowers unisexual, staminate and pistillate on different plants, submersed, short-pedicellate to nearly sessile; petals absent. Staminate flowers: filaments distinct; anthers linear; pollen embedded in gelatinous matrix, in moniliform chains. Pistillate flowers: ovary 1-locular; styles 6–8, not 2-fid. Fruits spheric, echinate, dehiscing into 6–8 irregular valves. Seeds pyriform; seed coat ephemeral.

Distribution

North America, Central America, Africa, Asia, Australia.

Discussion

Species 2 (1 in flora).

Selected References

Grey, W. F. and M. D. Moffler. 1978. Flowering of the seagrass Thalassia testudinum (Hydrocharitaceae) in the Tampa Bay, Florida area. Aquatic Bot. 5: 251--259.

Moffler, M. D., M. J. Durako, and W. F. Grey. 1981. Observations on the reproductive ecology of Thalassia testudinum (Hydrocharitaceae) in Tampa Bay, Florida. Aquatic Bot. 10: 183--187.

Moore, D. R. 1963. Distribution of the sea grass, Thalassia, in the United States. Bull. Mar. Sci. Gulf Caribbean 13: 329--342.

Orpurt, P. R. and L. L. Boral. 1964. The flowers and seeds of Thalassia testudinum König. Bull. Mar. Sci. Gulf Caribbean 14: 296--302.

Lower Taxa

Thalassia testudinum