50 HYDROCHARITAOEAE. 1. Ottelia. 



Family 19— HYDROCHARITAOEAE. 



Flowers mostly unisexual, enclosed when young in a spathe ; sepals and petals 3 . 

 stamens 3-12, anthers 2-ceiled ; ovary inferior, adherent to the receptacle, more or less 

 i -celled, with numerous ovules attached to parietal placentas : style wjth 3-8 stigmas 

 fruit indehiscent, ripening under waiter. Submerged water-plants. 

 A. Freshwater plants. 



B. Flowers large, bisexual Ottelia 1. 



B. Flowers small, dioecious. 

 C. Leaves long and radical. 



iSpathe tubular ; petals preseut Blyxa 2. 



Spathe ovoid ; petals absent in the male flowers . . Vallisneria 3. 



C. Leaves short, whorled Hydrilla 4. 



A. Saltwater plant ; leaves broad, in pairs Halophila 5. 



1. OTTELIA, Pers. 

 (From ottel-ambel, the native name of an Indian species.) 

 1. 0. ovalifolia (R. Br.), L. C. Rich. Leaves radical, on long petioles, mostly with 

 ovate or oblong blades floating on the water ; flowers bisexual, solitary and sessile within 

 a 2-lobed tubular 6-ribbed spathe at the summit of the peduncle ; calyx -lobes green, 2-3 

 cm. long ; petals longer ; stamens 6-12 ; stigmas 6-8, 2-lobed ; ovules numerous, anatro- 

 pous, on 6-8 protruding placentas. 



Reedbeds ; Rivers Murray, Onkaparinga, Glenelg, and other fresh waters. Jan. -March. 



2. BLYXA, Noronha. 



1. B. octandra, (Roxb.), Planch. Leaves long and grasslike, submerged; flowers 

 dioecious, on slender peduncles, the males several, protruding from a 2 -toothed tubular 

 spathe ; stamens about 8 ; sepals 3, about 5 mm. long ; petals 3, twice as long ; female 

 flowers solitary within a longer spathe ; stigmas 3 ; ovules numerous on 3 placentas, 

 anatropous. — B. Roxburghii, Rich. 



Recorded by Bentham from " waters near Lake Torrens, F. Mueller" but does not 

 appear to have been found since then. It occurs in Northern Australia and tropical Asia 



3. VALLISNERIA, Mich. 

 (After Antonio Vallisnieri, an Italian doctor and botanist, 1661-1730.) 



1. V. spiralis, L. Rootstock stoloniferous ; leaves all submerged and radical, long, 

 linear, usually minutely toothed towards the summit ; flowers dioecious, the males 

 minute, numerous in an ovoid 3-lobed pedunculate spathe, the male flowers pedicellate, 

 with 2-3 stamens and 3 sepals, the females solitary in a tubular bifid spathe, on a long 

 filiform spirally coiled peduncle, which unfolds so as to enable the flower to reach the 

 surface ; calyx-lobes 3 ; petals 3, rudimentary ; ovary 1 -celled, with 3 parietal placentas ; 

 ovules orthotropous. 



Chiefly in rivers and streams. Jan. -Mar. A tropical and subtropical plant in all 

 parts of the world. 



4. HYDRILLA, Rich. 

 (A diminutive of Hydra, the water serpent slain by Hercules.) 

 1. H. verticillata (L.), Casp. Leaves lanceolate, serrulate, about 1 cm. long, in whorls 

 of 4-8 along the submerged stems and branches ; flowers dioecious, solitary in short 

 tubular spathes ; male spathes on short peduncles ; stamens 3 ; female spathes sessile 

 and solitary, shorter than the leaves ; sepals and petals 3 ; ovary cylindrical, 1 -celled 

 with 3 parietal placentas ; ovules orthotropous ; style long with 3 filiform stigmas. 

 River Murray. 



5. HALOPHILA, Thou. 

 (Greek hals, halos, the sea ; philos, lover.) 



1. H. ovalis (R. Br.), Hook f. Submarine plant ; leaves in pairs at each node, oblong- 

 lanceolate, 2-7 cm. long, with a central nerve, 2 fine marginal nerves and about 20 oblique 

 secondary nerves, the 2 petioles long and slender and furnished at base with 2 broad 

 scarious scales ; flowers unisexual, solitary within a 2 -leaved sessile axillary spathe ; 

 male flowers pedicellate and emerging from the spathe, the females sessile within it ; 

 sepals 3 ; anthers 3, sessile ; pollen filiform ; ovary 1 -celled, tapering into a long beak, 

 at the summit of which are the 3 minute sepals of the female flower and 3 long filiform 

 stigmas ; fruit ovoid, membranous about 10 mm. long ; seeds numerous, with a loose 

 hyaline testa and smooth white endopleura ; embryo with a large hypocotyl and the 

 cotyledon coiled horizontally above it. 



Sea-coasts. Nov. -Jan. 



