3-42 
90. POTAMOGETONE^. 
suions from its upper axils. L. all beautifully transparent and 
netted with veins, the upper often nearly sessile and nearly orbi- 
cular, sometimes slightly cusj)idate. Fr. not exceeding 1 line in 
length. — Stagnant peaty water. P. VI. VII. 
4. P. riifesce?is (Schrad.); submersed Z. lanceolate narrowed 
at both ends subsessile membranous ])elhicid entire not apiculate, 
doatiug 1. subeoriaeeous obovate obtuse narrowed into a short 
})etiole, sti]). without wings, fr. acutely keeled, peduncles equal. 
— E.B. 128(). R. vii. t. 32. P.Jluitans Sm. — St. simple. Upper 
1. alone slightly coriaceous, often tinged with purple, longer than 
their stalks ; submersed 1. all nearly, if not quite, sessile, with 
chainlike reticulations near the midrib. Sep. “transversely oval.” 
— [P. spathulatus (Schr.) differs from this by having lonff stalks 
to all its leaves and the upper ones truly coriaceous. Is it a na- 
tive?] — Ditches and slow streams. P. VII. 
5. P. lanceolatus (Sm.) ■, submersed 1. lanceolate sessile nar- 
rowed at both ends entire not apiculate, floating 1. subeoriaeeous 
elliptic-lanceolate stalked, stij). linear-lanceolate acute iqjpermost 
broader, fr , peduncles equal. — E. B. 1985. not R. P.nigres- 
cens Fries? — St. veiy slender, slightly branched, floating 1. not 
always present, submersed 1. with ebainlike reticulations near the 
midrib. Ujjpermost stip. a])parently with 2 stronger dorsal ribs. 
Fr. unknown. — Streams, rare. Rivulet between Bodafon and 
Lligwy, Anglesea. Angus. Kincardineshire. Elgin. P. VII. 
VIII. E. S. 
6. P. heterophyllus (Schreb.) ; submersed 1. lanceolate narrowed 
at both ends sessile denticulate and apiculate, floating 1. sub- 
coriaceous elliptical stalked, stip. broadly lanceolate obtuse with 
2 stout prominent ribs, lower ones linear-lanceolate, /r. obtuse on 
the back, peduncles swelling upwards. — E. B. 1285. R. vii. t. 41- 
43. P. gramineus Fries, Koch. — St. much branched below. 
Lower stip. w'ithout the two strong ribs and equally nerved, upper 
ones widely spreading. Dry fr. slightly marked with 3 ridges on 
the back. — [P. nitens (Weber) has the submersed 1. rounded and 
clasping at the base and the floating 1. more coriaceous.] — Ponds 
and ditches. P. VI. VII. 
** L. all submersed, membranous, lanceolate or broader ; 
stipules free. 
7. P. lucens (L.) ; 1. pellucid oval lanceolate stalked denticu- 
late and apiculate, stip. winged, fr. “ obtuse on the back and 
slightly keeled when fresh,” peduncles swelling upwards, spikes 
eyiindncal densely flowered. — E. B. 3/6. R. vii. t. 36. — Com- 
bined by some authors with P. heterophyllus, but a])pears to be 
sufficiently distinct. All the stipules have two prominent wings 
on their back and are longer and narrower in proportion. Spikes 
