442 95. I'OTAMOGETOSACE.E. 



edge straight icith a tooth near its base keeled, style facial.- 

 E. B. S. 2609. E. vii. t. 26. Ped. very short. Spikes 4 (3- 

 ilowered. L. gradually acuminate. Styles hooked, continuing 

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



23. P. obtusifolius (M. & K.) ; st. slightly compressed with 

 rounded edges, /. linear 3-veined, spikes ovate den*c. continuous 

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

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

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

 oft' 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. VII. E. S. L 



24. P. Fries 'ii (Rupr.) ; st. slightly compressed, /. linear 

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

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

 ovate bluntly keeled. P. compressus Sm. E. B. 418. R. vii. 24, 

 not Fries, nor Koch. P. mucronatus (Schrad.) ed. viii. 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. 21 rather than Sp. 23. Ditches. P. VI. VII. 



E. S. I. 



25. P. pusil'lus (L.) ; st. subterete, /. linear [usually] 3-veined, 

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

 roundish-reniform, fr. obliquely ovats bluntly 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 thick- 

 ened. [j8. tenuissimus (M. & K.) ; 1. very narrow 1-vcined, fr. more 

 compressed. R. vii. 22, f. 39. 7. P. Berchtoldi (Fieber) ; 1. shorter and 

 broader, fr. thicker more distinctly warty. E. vii. 22. f. 37. S. Sturrockii 

 (Ar. Benn.) ; st. very slender somewhat compressed, 1. extremely thin 

 obtuse mucronate 3-5- veined ; ped. very slender, beak of fr. short, j 

 Ponds and ditches. P. VI. E. S. I. 



26. P. rutilus (Wolfg.) ; st. slender compressed, 1. linear the lowest (soon 

 decaying) quite obtuse the upper with long acuminate points, with 1 pair 

 of well-marked lateral veins, extending almost to the apex, stip. long 

 often with a long tapering point, ped. 2 3 times as long as the rather 

 dense spike, fr. oblong elliptic with obscure keel, inner edge nearly straight. 

 E. vii. 23. J. of S. xxxviii (1900) t. 407. L. tinner and much more 

 acute and the fr. less oblique than in Sp. 25. Recorded from Sussex, 

 Warw. or Staff., Anglesea. P. VII. E. 



27. P. trichoides (Cham.) ; st. subterete, /. subsetaceous 1- 

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

 versely reniforin obscurely keeled, straight inner edge with a 

 tooth near its base. $y. E. B. 1420. R. vii. 21. St. very 



