78 14- HYDROCHARITACEAE— 15. TRIURIDACEAE 



4. Spathes of the male flowers 2 — lu-flowered, not breaking away from the 



stem. Stamens 3 — 9. Ovules inverted. — Species 3. Madagascar and 



Angola. [Tribe BLYXEAE.] Blyxa Noronha 



Spathes of the male flowers many-flowered, breaking away from the stem. 

 Stamens 2—3. Ovules straight. [Tribe VALLISNERIEAE.] . 5 



5. Male flowers regular, with 3 fertile and 2 — 4 sterile stamens. Stigmas 



linear, 2-cleft or 2-parted. Leaves one-nerved. Stem elongated — 

 Species 10. Tropical and South Africa. . . . Lagarosiphon Harv. 

 Male flowers somewhat irregular, with 2 — 3 fertile stamens and sometimes 

 a sterile one. Stigmas ovate, notched or two-toothed. Leaves several- 

 nerved. — Species 2. North and Central Africa. Used in refining sugar. 



Vallisneria Mich. 



6. Leaves in two rows. Ovules inverted, inserted in the angles formed by the 



placentas and the wall of the ovary. Radicle of the embryo strongly 

 developed. Marine plants. [Subfamily THALASSIOIDEAE.] . 7 

 Leaves in rosettes. Ovules inverted, but inserted on the whole surface 

 of the placentas, or straight. Radicle of. the embryo not strongly 

 developed. Freshwater plants. [Subfamily STRATIOTOIDEAE.] 8 



7. Scape of the male flowers short, of the female long and at length spirally 



twisted. Male spathes several-flowered ; flowers with 3 petals and 3 

 stamens. — Species i. Madagascar and Red Sea. Yields fibres and 



edible seeds Enalus L. C. Rich. 



Scapes moderately long, not spirally twisted. Male spathes one-flowered ; 

 flowers without petals, with 6 stamens. — Species i. East Africa. 



Thalassia Soland. 



8. Placentas undivided. Ovules straight. Fertile stamens 9. Stem emit- 



ting runners. Leaves floating. — Species i. Algeria and Madagascar. 

 " Frogbit." [Tribe HYDROCHARITEAE.] . . Hydrocharis L. 

 Placentas two-cleft. Ovules inverted. Seeds very numerous. Fertile 

 stamens 6 — 12. Stem very short, without runners. Leaves at least 

 partially submerged. [Tribe OTTELIEAE.] 9 



9. Flowers hermaphrodite. Spathes one-flowered. Stigmas 6. — Species 9. 



Tropics and Egypt. Some are used as vegetables. (Plate 7.) 



Ottelia Pers. 

 Flowers dioecious. Spathes of the male flowers several-flowered. Stigmas 

 9 — 15. — Species 10. Tropics. Some are used as vegetables. 



Boottia Wall. 



ORDER TRIURIDALES 



FAMILY 15. TRIURIDACEAE 



Small, pale, yellowish or reddish herbs. Leaves reduced to scales. Flowers 

 in racemes, regular, monoecious. Perianth of 6 petaloid, valvate segments 

 united at the base. Stamens 3 ; filaments short or wanting ; anthers 2-cellcd, 

 opening transversely. Carpels inserted on a convex or conical receptacle, 



