Potamogeton.] 



CLIII. NAIADACEiE (bENNETT). 



219 



3. POTAMOGETON, Linn.; Benth. et Hook. f. Gen. PI. iii. lOU. 



Perianth-segments 4, green, valvate. Anthers 4, sessile, with two 

 roundish cells. Carpels 4 (some abortive), sessile, 1-celled, 1-ovuled ; 

 ovules campylotropous ; stigma persistent, subsessile or decurrent, 

 altering much in position in ripening. Drupelets small, variable in 

 shape, coriaceous. Seeds subreniform ; radicle large. — Submerged 

 water-plants with creeping rootstocks. Stems terete or compressed. 

 Leaves often floating (rarely aerial), alternate or opposite, entire or 

 toothed ; stipules intrafoliaceous, free or adnate to the petiole. Flowers 

 small ; spicate ; bases of the peduncles enclosed in a membranous spathe, 

 ebracteate. 



submerged 



3. 



Species 65-75, cosmopolitan. 

 'Floating leaves present, coriaceous. 



Fruit 3-keeled ; stems moderately stout 

 leaves few or none. 

 Leaves tapering to the base .... 



Leaves obtuse at the base ..... 



Fruit sharply 3-keeled ; stems moderately stout ; 

 submerged leaves abundant .... 



Fruit 3-keeled ; stems filiform ; submerged leaves 

 abundant ....... 



floating leaves none. 

 Leaves 2-12 lin. broad. 



Leaves crisped, serrulate ; fruit long-beaked 

 Leaves flat, entire. 



Fruit large, obliquely obtuse .... 



Fruit small, pointed ..... 



Leaves less than 2 lin. broad. 

 Stipules free. 



Leaves straight, l-3-nei*ved ; nerves equal 

 Leaves curved, 1-3-nerved ; central nerve very 

 broad ....... 



Stipules adnate to the leaf-bases. 



Style on the ventral margin .... 



Style central. 



Leaves all setaceous or linear-setaceous 

 Lower leaves ^-^^ in. wide, very rigid, upper 



linear to filiform ... .12 



P.Jluilans. 

 P. Richardi. 



P. Schweinfurthii. 



P.javanicus. 



5. P. crispui 



]0. 



11. 



P. lucens. 

 P. coloraium. 



P. pusillum. 

 P. Preussii. 

 P. pectinutum. 

 P.filifomie. 

 P. Livingsfonei. 



1. P. fluitans, Both, Tent. Fl. Germ. i. 72. Stem stout. Sub- 

 merged leaves translucent, linear-lanceolate ; floating leaves ovate or 

 ovate-lanceolate, long-stalked, tapering at either end, not plicate ; 

 stipules large, blunt. Peduncles stout ; spike dense-flowered ; no ripe 

 fruit seen on African or European specimens. — A. Bennett in Dyer, 

 Fl. Cap. vii. 46 ; Rendle in Cat. Afr. PI. Welw. ii. 94. P. nataiis, vai-. 

 fluitans, Cham. Adnot. Fl. Berol. 4. 



Kower Guinea. Angola : Huilla, Welwitsch, 249 ! 



Also in North and South Africa, Madagascar, Europe and Asia. 



2. P. Richardi, Solms-Lauh. in Schweinf. Beitr. FL Aethiop, 

 194, and 292. Stem stout. Submerged leaves few, finer in texture 



