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Published In: Genera Plantarum 67. 1789. (4 Aug 1789) (Gen. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 6/2/2011)
Acceptance : Accepted
Project Data     (Last Modified On 6/3/2011)
Contributor Text: ABDUL GHAFOOR
Contributor Institution: Department of Botany, University of Karachi, Karachi.
General/Distribution: A family of c. 17 genera and 76 species, distributed in marine, saline or fresh waters in tropical, subtropical and temperate regions. Represented in Pakistan by 6 genera and 6 species.
Comment/Acknowledgements: There are several extraordinary pollination mechanisms throughout the family, as in Hydrilla and Vallisneria (Cook, C.D.K. in Symoens, J.J. et al. (ed.) Studies in Aquatic Vascular Plants pp. 1-15,1982).

Acknowledgements: We are grateful to Prof. Dr. C.D.K. Cook (Botanischer Garten and Institut fur Systematische Botanik der Universitat Zurich, Switzerland) and Mr. I.C. Hedge (Edinburgh) for going through the manuscript and offering suggestions for its improvement. The financial assistance received from the United States Department of Agriculture under P.L. 480 with the coordination of the Pakistan Agriculture Research Council, Islamabad, is thankfully acknowledged.


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Annual or perennial, monoecious or dioecious, mostly submerged aquatic herbs in fresh or saline waters. Stem corm-like or slender, stoloniferous or not. Leaves exstipulate, sessile or petiolate, radical or cauline and spirally whorled, opposite or alternate, submerged, rarely partly emergent or floating, variously shaped; veins ± parallel, straight or curved. Flowers solitary or clustered, enclosed at first by a bifid sessile or long stalked pair of opposite united and spathe-like or free bracts, bisexual or unisexual, when unisexual then males usually more than 1, females solitary, actinomorphic or occasionally ± zygomorphic, mostly 3-merous. Sepals 3, free, often green, valvate. Petals 3 or absent, membranous, showy or minute and inconspicuous, imbricate, or con¬volute. Stamens (1-) 2 to numerous, uni or multiseriate, inner ones rarely staminodial, filaments ± slender free or united in pairs, rarely absent; anthers dithecous, dehiscing by parallel longitudinal slits; 1 or more pistillodes usually present in male flowers. Ovary inferior, composed of 2-15 fused carpels, linear, lancecolate or ovate, generally protruding into a filiform beak or rostrum at the apex, unilocular with parietal placentation and numerous orthotropous to anatropous, erect to pendulous, bitegmic ovules; styles as many as carpels, entire or 2-lobed. Fruit ripening under water, linear-lanceolate, ovate to globose, dry or pulpy, many-seeded, dehiscing irregularly. Seeds fusiform, elliptic, ovate or globose, glabrous, warty or spinose, exalbuminous; embryo upright.

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1 Freshwater or brackish herbs (2)
+ Marine herbs 6 Halophila
2 (1) Stems short, with or without stolons. Leaves all radical or in rosettes. Spathes peduncled (3)
+ Stems elongated. Leaves cauline, whorled or the lowest opposite. Spathes sessile in leaf axils 1 Hydrilla
3 (2) Leaves without a distinct petiole (4)
+ Leaves differentiated into blade and petiole (5)
4 (3) Leaves parallel sided for most of length, obtuse. Peduncle of female flowers long, spirally coiled after fertilization. Petals minute or vestigial. Ovary not long, not rostrate 3 Vallisneria
+ Leaves attenuate acute. Peduncle of female flowers not spirally coiled after fertilization. Petals large and conspicuous. Ovary long and rostrate 2 Blyxa
5 (3) Plants stoloniferous. Stipules present. Ovary beakless. Spathe not winged 5 Hydrocharis
+ Plants without stolons. Stipules absent. Ovary beaked. Spathe winged or spinose 4 Ottelia
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