380 95. POIAMOGEIONACB^. 



ing below, simple. Petioles plane-concave. L. subcordate belo-w, 

 when pressed flat a ridge is formed on eacb side of the base, 

 jointed to their stalks a little below the limb. Sep. stalked, roundly 

 rhomboidal. Anth. -cells not parallel. Fr. greenish, slightly 

 compressed, IJ — 2 lin. long. — Ponds, ditches, and slow streams. 

 P. VI. VII. E. S. I. 



2. P. polygonifdlius (Pourr.) ; 1. all stalked, upper subcori- 

 aceous floating oblong-eUiptic subcuspidate, no leafless petioles, 

 lower 1. linear-lanceolate, /r. OTOTMfe blunt and rounded on the 

 back, peduncle equal. — P. oblongus Viv., M. B. S. 2849. — St. 

 creeping below. Petioles longer than leaves, convex on both 

 sides, not jointed below the limb. Lower 1. often very narroyf. 

 Spikes rather short and irregular. Sep. transversely elliptic, 

 stalked. Fr. reddish, scarcely compressed, 1 lin. long ; a faint 

 keel and lateral ridges when dry. — (3. pseudo-fluitan^ (Syme) ; 

 submerged 1. membranous linear-lanceolate narrowed at both 

 ends. — ^Ditches, small streams, and ponds. /3. Buttermere. Gap 

 of Dunloe, Kerry. P. VII. E. S. I. 



3. P. plantagin' eus (Ducr.) ; I. all shortly stalked membranous 

 and pellucid blunt not cuspidate nor plicate, upper elliptic, lower 

 1. oblong,//-, minute rounded on the back when fresb keeled wlien 

 dry, peduncle equal.—.©. B. S. 2848. B. vii. 45. — St. cre^ing 

 below, branched, sometimes throwing out long runners from 

 its upper axils. L. all beautifully transparent and netted with 

 veins, the upper often almost sessile and nearly orbicular, some- 

 times slightly cuspidate. Petioles plane-concave above. Spikes 

 long, cylindrical. Anth.-oells nearly parallel. Sep. ovate. Fr. 

 greenish, f lin. long. — Stagnant peaty water. P. VI. VII. 



E. S. I. 



4. P. rufes'cens (Schrad.) ; submersed I. lanceolate narrowed 

 at both ends subsessile membranous pellucid entire not apieulate 

 with chainlike network nearthe midrib, floating 1. subcoriaceous, 

 obovate blunt narrowed into a short petiole, stip. without wings, 

 fr. acutely keeled, peduncle equal.— JS. 5. 1286. iJ.vii.32. P. 



Jluitans 8m. — St. simple. Upper 1. alone slightly coriaceous, 

 often tinged with purple, longer than their stalks ; submersed 

 1. all nearly, if not quite, sessile. Sep. " transversely oval." — 

 Ditches and slow streams. P. VII. E. S. I. 



5. P. lanceoldtiis (Sm.) ; submersed 1. linear-lanceolate ses'jile 

 entire acute not apieulate with chainlike network near the midrib, 

 floating 1. subcoriaceous elliptic-lanceolate shortly stalked, stip. 

 almost subulate uppermost broader with 2 dorsal" elevated ribs, 

 peduncles equal from uppermost floating opposite leaves. — E. B. 

 1985. J. o/B. xix. t. 217 (not iJ.).- St. very slender, slightly 



