POTAMOGETON. 341 
2848. R. vil. 45.—St. creeping below, branched, sometimes 
throwing out long scions from its upper axils. _L. all beautifully 
transparent and netted with veins, the upper often nearly sessile 
and nearly orbicular, sometimes slightly cuspidate. Spikes long, 
cylindrical. Sep. ovate. Fr. greenish, $ lin. long.—Stagnant 
peaty water. P. VI. VII. 
4. P. rufescens (Schrad.) ; submersed 1. lanceolate narrowed 
at both ends subsessile membranous pellucid entire not apiculate, 
floating 1. subcoriaceous obovate obtuse narrowed into a short 
petiole, stip. without wings, fr. acutely keeled, peduncles equal. 
—E. B. 1286. R. vii. 32. P. fluitans Sm.—St. simple. Upper 
L 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.” 
—Ditches and slow streams. P. VII. 
5. P. lanceolatus (Sm.); swbmersed 1. lanceolate narrowed at 
both ends entire not apiculate, floating 1. subcoriaceous elliptic- 
lanceolate stalked, stip. lmear-lanceolate acute uppermost broader, 
ff .33548% , peduncles equal. EE. B, 1985. (not BR.) P. nigrescens 
Fries ?—St. very slender, slightly branched, floating 1. not always 
present, submersed 1. with chainlike reticulations near the midrib. 
Uppermost stip. apparently with 2 stronger dorsal ribs. Fr. un- 
known.—Streams, rare. P. VII. VIII. E. 8. 
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 sith 
2 stout prominent ribs, lower ones linear-lanceolate, fr. obtuse on 
the back, peduncles swelling upwards.—E. B. 1285. R. vu. 41—- 
43. P. gramineus Fries, Koch.—St. much branched below. 
Lower stip. without 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 their base.]—Ponds and ditches. P. VI. VII. 
** T,, all submersed, membranous, lanceolate or broader ; 
stipules free. 
7. P. lucens (L.); 1. pellucid oval lanceolate stalked dentecu- 
late and apiculate, stip. winged, fr. obtuse on the back and slightly 
keeled when fresh, peduncles swelling upwards, spikes cylindrical 
densely flowered.—E. B.376. R. vii. 36.—All the stipules have 
two prominent wings on their back. Spikes long, about equal- 
ling the peduncles. According to Mr. W. Wilson “ ovate-lanceo- 
late moderately acute coriaceous 1.” sometimes occur. When the 
dimb of the 1. is much reduced in size and the midrib promment 
and resembling a long spine, it is the P, acuminatus Schum.— 
Common in deepish water. P. VI. 
