93- PODOSTEMONACEAE — 94. HYDROSTACHYACEAE 231 



1. Flowers without a spathe, regular. Perianth 3-parted. Stamen i. 



Ovary 3-celled. Styles 3. Leaves undivided. — Species 5. Tropical 

 and South Africa. (Plate 57.) [Tribe TRISTICHEAE.] 



Tristicha Thouars 



Flowers at first enclosed in a spathe, irregular. Perianth of 2, rarely of 



3 small scales. Stamens 2 — 4. Ovary i — 2-celled. Styles i — 2. 



Leaves usually dissected 2 



2. Style I, very short ; stigma entire. Ovary i-celled. Stamens 3 — 4 ; 



filaments free or nearly so. Stem elongate. Spathe close to the flower. 

 — Species i. Southern West Africa (Angola). [Tribe MARATHRE- 



AE."; Angolaea Wedd. 



Styles 2, free or united at the base. Stamens 2, rarely [Winlderella) 3, 

 but then filaments imited about halfway up. [Tribe PODOSTE- 

 MONEAE.] 3 



3. Filaments free or nearly so. Ovary stalked 4 



Filaments obviously united 5 



4. Fruit with unequal valves, the persistent valve 5-nerved, the deciduous 



one 3-nerved. Stem little branched. Leaves linear or the lower with 



two teeth at the base. — Species i. West Africa (Cameroons). 



Ledermanniella Engl. 

 Fruit with two equal, persistent, linear, 5-nerved valves. Stem much 



branched. Leaves divided in 2 — 5 narrow segments. — Species 2. 



West Africa. Used as salad. Dicraeanthus Engl. 



•5. Ovar\^ and fruit i -celled, the latter with somewhat unequal valves. Flowers 



drooping. — Species 4. Central and South Africa. Used as salad. 



(Including Isnthylax Baill.) Sphaerothylax Bisch. 



Ovary and fruit 2-celled 6 



6. Fruit with unequal valves, one of which falls off, and with prominent ribs. 



Pollen-grains united in pairs. — Species i. Madagascar. 



Podostemon Mich. 

 Fruit with equal valves 7 



7. Fruit smooth, without distinct ribs. Pollen-grains separate. Flowers 



drooping. — Species 3. Southern Central Africa. {Leiocarpodicraea 

 Engl., under Dicraea Thouars) Leiothylax Warm. 



Fruit with prominent ribs 8 



-8. Fruit 2-toothed at the top, with boat-shaped valves , one of them or both 

 falling off. Pollen-grains separate. — Species i. West Africa (Cam- 

 eroons) Winklerella Engl. 



Fruit with persistent valves. Pollen-grains united in pairs. — Species 9. 

 Tropics. (Under Podostemon Mich.) Dicraea Thouars 



FAMILY 94. HYDROSTACHYACEAE 



Aquatic herbs. Stem tuberous. Leaves with a sheath and a ligule. Flowers 

 in spikes, bracteate, without a perianth, dioecious Stamen i, with separated 



