1503 CXXV. HYDEOCHAEIDEiE. 



Tribe II. Vallisnerieee. — Stemless, or icith stolons only. Leaves sessile, long and 

 narrow. Spathes on long scapes. 



Flowers unisexual. Perianth single 2. VAtLisNEEU. 



Plowers uni or bi-sexual. Perianth double 3. Blyxa. 



Tkibe III. Stratiotese. — Stemless or with a creeping rootstoc/c. Spathes pedunculate. 

 Perianth douhle. Leaves various. 



Flowers unisexual. Male spathes 2 to 3 -fid: Ovary not beaked .... 4. Hydbooharis. 



Flowers unisexual, solitary. Fruit winged 5. Ottelia. 



Sebies 2. Marinas. — Saltwater herbs. 



Teibe IV. Thalassiese. — Spathes 2-leaved. Ovary beaked. 



Male spathes many-fid. Perianth double .6. Enhamts. 



Male spathes 1-fid. Perianth single 7. Halophila. 



1. HYDRILLA, Eich. 

 (From its appearing curled in water.) 



Flowers diceoious, both sexes solitary in a short tubular spathe. Male perianth 

 shortly pedunculate, the outer segments ovate and green, three inner onesoblong- 

 linear and petal-like. Stamens 3, with reniform anthers. Female perianth with 

 a long filiform tube above the ovary, the segments all petal-like and less unequal 

 than in the males. Style elongated, with 3 filiform stigmas. Ovary 1-celled, 

 with 3 parietal placenta. Fruit cylindrical, linear, with few seeds. — Submerged 

 herbs with branching stems and short verticillate leaves. Spathes sessile in the 

 axils. 



The genus is restricted by Caspary to the single species eommou in still and slowly running 

 waters o£ the tropical and temperate regions of the Old World, the Australian form being 

 the tyi)ical one originally described from India. — Benth. 



1. H. verticillata (verticillate), Casp. in Monatshav. Akad. Berl. 1857; 

 Benth. Fl. Austr. yi. 2i5d. Stems leafy throughout, much branched and floating 

 under water in large masses. Leaves all in whorls of 4 to 8, except a single 

 small sheathing one at the base of each branch and a pair only next above it, all 

 oblong-lanceolate or broadly linear, 2 to 4 lines long and serrulate. Female 

 spathes sessile and solitary, shorter than the leaves, the perianth-tube -J to 

 fin. long, the outer perianth-segments nearly 1|- line long, the inner ones 

 shorter and narrower. Fruit linear, with few seeds. — Serpicida verticUlnta, 

 Linn. f. Suppl. 416 ; Eoxb. Corom. PI. t. 161; Hydrilla ovalifolia, Eich. in Mem. 

 Inst. Fr. 1811, 76, t. 2 ; Vdora australis, F. v. M. Second Gen. Eep. 16. 



Hab.: Water-holes near Eookhampton, Bojc'Ka», O'Shanesy; near Herbert Elver, Dallachy ; 

 Mount Elliott, Fitzalan; Brisbane liiver. 



2. VALLISNERIA, Linn. 



(After Antonio Vallisneri.) 



Flowers dioecious. Males minute and very numerous in an ovoid-globular 

 3-lobed spathe. Perianth-segments B. Stamens 1 to 3 ; anthers with 2 globular 

 cells. Female flowers solitary and sessile in a narrow tubular 8-toothed spathe. 

 Perianth-tube not produced above the ovary ; segments 8. Staminodia (or inner 

 perianth-segments ?) 3, small, bifid, alternating with the perianth-segments. 

 Stigmas 3, broad, 2-dentate or bifid. Ovary narrow, with 3 perietal placentas. 

 Fruit narrow-cylindrical, enclosed in the spathe. Seeds numerous, cylindrical. — 

 Submerged herbs, the leaves and peduncles tufted at the bottom of the water 

 the leaves very long, without any lamina. 



Leaves with often a long portion floating, strap-like . 1. V. spiralis. 



Leaves very narrow like fine grass, submerged 2. V. gracilis. 



Stems leafy exceeding 18ia, in length 3. V. caulescens. 



The genus is generally distributed over the tropical and temperate regions of the New as 

 well a? the Old World, of the Queensland species one is most common over the whole area 

 the other two are e'ndfemio. ■ • - • 



