POTAMOGETON. 
lou<; 5 , about equalling the ])eduneles. Aecording to Mr. W. Wil- 
son “ ovate-laneeolate moderately acute coriaceous 1.” sometimes 
occur, but I suspect the existence of another species. — A variety 
is oeeasionally found with the limb of the 1. much reduced in size 
and the midrib prominent and resembling a long spine, which is, 
according to Koch, the P. aciminatus Sebum. — Common in 
(Icepisli water. P. VI. 
8. P. longifoUus (Gay) ; 1. pellucid elongate-lanceolate nar- 
rowed below entire a])iculate, stij). winged, fr peduncles 
very long swelling upwards, spikes with few subverticillate distant 
flowers. — E. B. S. 2847. — St. long, slender. L. distant, quite 
entire, nearly sessile with very short stalks. Stipules green, lan- 
ceolate, with 2 narrow wings on the back. Peduncles 6 — 8 in. 
long and much thicker than the stem, suddenly contracting at the 
spike which is about an inch long and has the fl. rather more de- 
cidedly whorled than they are represented in E. B. S. Fr. un- 
known. — Deep water. Lough Corrib, Galway. Mr. J. Ball. 
P. VIII. I. 
9. P. prmlongus (Wulf.) ; 1. pellucid elongate-oblong half- 
clasping obtuse and hooded at the end entire, stip. not winged, fr. 
rounded on the hack when fresh keeled when dry, peduncles very 
long equal, spikes many-flowered. — E. B. S. 2858. R. vii. t. 33. 
— St. long, growing in deep water and forming dense masses of 
foliage just below the surface. Peduncles 6 — 12 in. long. Spikes 
1 — 2 in. long. — Rivers and ditches, rare. P. VI. 
10. P. perfoliatus (L.) ; st. round, 1. pellucid cordate-ovate 
clasping serrulate plane, fr. rounded on the back when fresh, 
keeled when dry, peduncles equal. — E. B. 168. R. vii. t. 2.9. — 
St. long, slightly branched. Peduncles rather thick and short. 
Spikes short. — Lakes and streams. P. VII. 
11. P. crispus (L.); st. compressed, 1. pellucid linear-oblong 
obtuse sessile serridate wavy, fr. with a long beak keeled on the 
back when dry, peduncles equal. — E. B. 1012. R. vii. t. 29 — 30. 
— St. much branched. Peduncles elongated. Spikes few-flow- 
ered. Beak as long as the nut. L. usually crisped at the edges, 
occasionally plane when it is P. serratuin Huds. — Ditches and 
streams. P. VI. 
*** L. all submersed, alternate, linear ; stipules free. 
12. P. zoster cefolius (Schum.); st. flattened, 1. linear-acumi- 
nate with 3 principal ribs and numerous close parallel interme- 
diate nerves occupying the whole surface, spikes cylindrical upon 
long peduncles, sep. transversely oval, fr. obovate keeled, st 3 'le 
terminal. — E. B. S. 2685. R. vii. t. 27. P. cuspidatus Sm., P. 
compressus Fries, Koch. — Peduncles 2 — 4 in. long. Spikes 
