POTAMOGETON. 375 



E. B. 8. 2609. JJ. vii. t. 26.— Ped. very short. Spikes 4—6- 

 flowered. L. gradually acuminate. Styles hooked, continuing 

 the inner edge of the frnit. — Marsh ditches, rare. P. VI. E. 



18. P. ohtusifdUus (Koch); st. slightly compressed with 

 rounded edges, /. linear S-veined, spikes ovate dense continuous 

 ahout as long as the short ped., sep. rhomboidal, fr. obovate 

 keeled.— iJ. vii. t. 25. P. gramineus Sm., E. B. 2253.— St. 

 slender, much branched. Peduncles very short. L. rounded 

 oif to a slight point at the end, with oblong network near the 

 midrib, wanting the fine parallel veins of the two preceding 

 species. — Ponds and ditches, rare. P. VI. VH. E. S. I. 



19. P. mueronM'm (Schrad.) ; st. slightly compressed, I. linear 

 5-veined suddenly apiculate, spikes short lax J or f shorter than 

 the compressed clavate ped., sep. transversely oval, fr. obliquely 

 ovate bluntly keeled. — P. compressus Sm. E. B. 418. P.. vi:. 24, 

 not Pries, 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 Sp. 16 rather than Sp. 18. 

 —Ditches. P. VI. VH. E. S. I. 



20. P. pusiVhiS (L.) ; st. subterete, I. linear S-veined, spikes 

 short rather lax J or f shorter than the slender ped., sep. 

 roundish-reniform, fr. obliquely ovate bluntly keeled. — E. M. 

 216. P. 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. rutilus (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 P. pmillus.'] — Ponds and ditches. 

 P. VL E. S. I. 



21. P. trichffides (Cham.) ; st. subterete, I. subsetaceous 1- 

 veined finely pointed, spikes short lax long-stalked, fr. semicir- 

 cular compressed obscurely keeled, straight inner edge with a 

 tooth near its base. — Sy. E. B. 1420. P. vii. 21. — St. very 

 slender, a little thickened below the joinings ; branches fascicu- 

 late. 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.— About Norwich. P. VII. VHL E. 



**** Z. all submersed, alternate, linear, sheathing. 



22. P. JlabeUdtus (Bab.) ; lower I. broadly linear abruptly 

 apiculate or acuminate 3 — 5-veined with transverse veins, upper 

 I. nan'ow acute S-veined, fr. (2 liu. long) broadly ^-obovate 

 inner edge nearly straight but gibbous near the top rounded on 



