342 94. POTAMOGETONACEZ. 
8. P. longifolius (Gay); J. pellucid elongate-lanceolate nar- 
rowed below entire apiculate, stip. 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. Ped. 6—8 in. long, 
much thicker than the stem, suddenly contracting at the spike 
which is about an inch long and has the fl. rather more whorled 
than they are represented in FE. B.S. Fr. unknown.—Deep water. 
Lough Corrib, Galway. Mr. J. Ball. P. VIII. 
9. P. prelongus (Wulf.); 7. pellucid elongate-oblong half- 
clasping blunt and hooded at the end entire, styp. not winged, fr. 
rounded (rarely keeled) on the back when fresh keeled or winged 
when dry, peduncles very long equal, spikes many-flowered.— 
E. B.S, 2858. R. vii. 33.—St. long, growing in deep water and 
forming dense masses of foliage just below the surface. Pedun- 
cles 6—12 in. long. Spikes ]—2 in. long.—Rivers and ditches, 
rare. P. VI. 
10. P. perfoliatus (L.); st. round, 1. pellucid cordate-ovate 
clasping not hooded, fr. rounded on the back when fresh keeled 
when dry, peduncles equal—E. B. 168. R. vii. 29.—St. long, 
slightly branched. Peduncles rather thick and short. Spikes 
short.—Lakes and streams. P. VII. 
ll. P. erispus (L.); st. compressed, 1. pellucid linear-oblong 
blunt sessile serrate wavy, fr. with a long beak keeled on the 
back when dry, peduncles equal.— FE. B. 1012. RB. vii. 29—30. 
—St. much branched. Ped. elongated. Spikes few-flowered. 
Beak as long as the nut. L. usually erisped at the edges, occa- 
sionally flat (P. serratum Huds.).—Ditches and streams. P. VI. 
*** T,. all submersed, alternate, linear ; stipules free. 
12. P. zosterefolius (Schum.); st. flattened, J. linear-acumi- 
nate with 3 principal and numerous close parallel intermediate 
nerves occupying the whole surface, spikes cylindrical upon long 
peduncles, sep. transversely oval, fr. obovate keeled, style ter- 
minal.—#. B.S. 2685. R. vii. 27. P. cuspidatus Sm., P. com- 
pressus Fries, Koch.—Peduncles 2—4 in. long. Spikes 10—15- 
flowered. L. suddenly acuminate or apiculate.—Rivers and lakes. 
P. VI. E. 8. 
13. P. acutifolius (Link) ; st. flattened, J. lear acuminate with 
3 principal and numerous close parallel intermediate veins occu- 
pying the whole surface, spikes ovate about as long as the short 
peduncle, sep. rhomboidal, fr. reniform keeled, style facial.—» 
E. B. 8. 2609, _R. vu. t. 26.—Peduncles very short. Spikes 
4—6-flowered. L. gradually acuminate. Styles a continuation 
