Potamogeton.} CLIII, NAIADACE& (BENNETT). 219 
3. POTAMOGETON, Linn.; Benth. et Hook. f. Gen. Pl. iii. 1014. 
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 aérial), alternate or opposite, entire or 
toothed ; stipules intrafoliaceous, free or adnate to the petiole. Flowers 
small; spicate ; bases of the peduncles enclosed ina membranous spathe, 
ebracteate. 
Species 65~75, cosmopolitan. 
*Floating leaves present, coriaceous. 
Fruit 3-keeled ; stems moderately stout ; submerged 
leaves few or none. : 
Leaves tapering to the base. . . - 1. P. fluitans. 
Leaves obtuse at the base . . : : - 2. P. Richardi. 
Fruit sharply 3-keeled; stems moderately stout ; 
submerged leaves abundant . : : 
Fruit 3-keeled ; stems filiform; submerged leaves : : 
abundant , ‘ . . : . . 4. P. javanicus. 
**Floating leaves none. 
Leaves 2-12 lin. broad. 3 
Leaves crisped, serrulate ; fruit long-beaked . 5&. P.crtspum. 
Leaves flat, entire. 
Fruit large, obliquely obtuse . < : . 6. P. lucens. 
Fruit small, pointed x : . . 17. P. coloratum. 
Leaves less than 2 lin. broad. 
Stipules free. 
8. P. Schweinfurthii. 
Leaves straight, 1-3-nerved ; nerves equal . 8. P. pusillum. 
Leaves curved, 1~3-nerved; centra] nerve very 2 
broad. 3 = : eee . 9. P. Preussiz. 
Stipules adnate to the leaf-bases, be 
Style on the ventral margin . . . - 10. P. pectinatum, 
Style central. : 
Leaves all setaceous or linear-setaceous . ll. P. filiforme. 
Lower leaves 4-5, in. wide, very rigid, upper oh : 
linear to filiform . ‘ ; . 12. P. Livingstone. 
1, P. fluitans, Roth, Tent. Fl. Germ. i. 72. Stem stout. — 
merged leaves translucent, linear-lanceolate ; floating leaves bie id 
ovate-lanceolate, long-stalked, tapering at either end, ved Pp soe ; 
stipules large, blunt. Peduncles stout; spike dense-flowere 3 i. pe 
fruit seen on African or European specimens.—A. Bennett in Dyer, 
Fl. Cap. vii. 46; Rendle in Cat. Afr. Pl. Welw. ii. 94. P. natans, var. 
fuitans, Cham. Adnot. Fl. Berol. 4. 
Lower Guinea. Angola: Huilla, Welwitsch, 249! 
Also in North and South Africa, Madagascar, Europe and Asia. 
2. P. Richardi, Solms-Laub. in Schweinf. Beitr. Fl. suns 
194, and 292. Stem stout. Submerged leaves few, finer in texture 
