354 
94. POTAMOGETONACE^. 
3 principal and inany close parallel intermediate veins occu- 
pying the whole surface, spikes ovate about as long as the short 
ped., Sep. rhomboidal, fr. broadly ^-obovate compressed inner 
edge straight with a tooth near its base keeled, style facial.— 
E. B. S. 2609. E. vii. t. 26.— Ped. veiy short. Spikes 4—6- 
flowered. L. gradually acuminate. Styles hooked, continuing 
the inner edge of the fiuit. — Marsh ditches. Sussex. Hertf. 
Norfolk. P. VI. E. I. 
15. P. gramin'eus (L. Sm.) ; st. slightly compressed with 
rounded edges, /. linear S-veined, spikes ovate dense cmitinuoiis 
about as long as the short ped., sep. rhomboidal, fr. obovate 
keeled.— j;. B. 2253. Ray Syn. t. 4. P. obtusifolius Koch, P. 
vii. t. 25. — St. slender, much branched. Peduncles very short. 
L. rounded off to a slight point at the end, with oblong network 
near the midrib^ wanting the fine parallel veins of the two pre- 
ceding species. — Ponds and ditches, rare. P. VI. VII. E. S. I. 
16. P. conipres'sus (L.) ; st. slightly compressed, I. linear 
5-veined suddenly apiculate, spikes short lax 2 or 3 times shorter 
than the compressed clavate ped., sep. ti'ansversely oval, fr. ob- 
liquely ovate bluntly keeled. — E. B. 418. P. vii. 24, not Fries 
nor Koch. — Lateral veins nearer together and nearer to the 
margin of the 1. than to the midrib (rarely some 1. are 3-veined ), 
no intermediate veins. — Like No. 15 rather than 17. — Ditches. 
17. P. pusil'lus (L.) ; st. subterete, I. linear ^-veined, spikes 
short rather lax 2 or .3 times shorter than the slender ped., sep. 
roundish-reniform, fr. obliquely ovate bhmtly keeled. — E. B. 
215. R. vii. 22. — St. slender. L. narrow, rather acute, without, 
intermediate parallel veins, the lateral veins equidistant between 
the midrib and margin. Ped. scarcely compressed, not thickened. 
— [P. rutilm (Wolfg., Fries) has 3-veined attenuate-cuspidate 1., 
semiterete st., and oblong-elliptic fr. without a keel. — P. gra- 
cilis of Man. ed. 4. seems to be F. pitsillus.] — Ponds and ditches. 
P. VI. E. S. I. 
18. P. trichoides (Cham.) ; st. subterete, I. sitbsetaceous 1- 
veined finely pointed, spikes short lax long-stalked, fr. semicir- 
cular compressed obscurely keeled, straight inner edge tcith a 
tooth near its base. — R. vii. 21. — St. very slender, a little 
thickened below the joinings; branches fasciculate. L. not 
transversely veined. Floral stip. large. Ped. not thickened. 
Sep. roundish, stalked. Monandrous. Fr. often warted on the 
back and with a tubercle on each side at its base when fresh. — 
**** L. all submersed, alternate, linear, sheathing. 
19. P. Jtabelldtu-s (Bab.) ; lower I. broadly linear abruptly 
P. VI. vn. 
E. S. 1. 
About Norwich. P. VII. VHI. 
E. 
