FLORA OF TROPICAL AFRICA. 



Order CXXXI. HYDROCHARIDEiE. (By C. H. Wright.) 



Flowers regular, unisexual, rarely hermaphrodite, enclosed in a 

 tubular or inflated spathe. Perianth 2- rarely 1 -seriate, 3-merous, 

 inner whorl petaloid, white or yellow. Stamens 3-12 ; filaments very 

 short ; anthers usually oblong. Ovary inferior, 1-celled, with 3-6 

 parietal placentas ; more rarely several-celled by the intrusion of the 

 placentas. Style divided. Ovules many, orthotropous or anatropous. — 

 Aquatic, usually submerged, herbs. Stem short, stoloniferous or elon- 

 gated and leafy all over. Leaves linear, lanceolate or broadly ovate. 

 Spathes axillary, solitary, monoecious or dioecious. 



An order containing about 50 species, extending through the tropical and temperate 

 regions of both hemispheres. 



Stem elongated, leafy. Freshwater. 



Leaves verticillate. Male spathe l-flowered . . .1. Hydrilla. 



Leaves alternate or opposite. Male spathe many-flowered 2. Lagaeosipiion. 

 Stems very short; leaves radical. Freshwater. 



Perianth simple ........ 3. Valltsneria. 



Perianth double. 



Styles 3 4. Bltxa. 



Styles 6-15. 



Flowers hermaphrodite ...... 5. Ottelia. 



Flowers unisexual ...... 6. Boottia. 



Rhizome creeping. Marine. 



Stamens 6 , . . ..... 7. Thalassia. 



Stamens 3 .8. Halophila. 



1. HYDRILLA, L. C. Rich. ; Benth. et Hook. f. Gen. PI. iii. 450. 



Dioecious. Male spathe sessile in the axil of the leaf, l-flowered, 

 turbinate, bursting irregularly. Perianth double ; outer segments 3, 

 ovate, acute, inner linear. Stamens 3 ; filaments thick ; anther ovate, 

 2-celled, with longitudinal dehiscence. Rudiment of ovary none. 



