POTAMOGrETOX. 441 



denticulate ) nearly sessile, with very sliort stalks. Stip. green, 

 lanceolate, with 2 narrow wings on the back. Ped. 6 8 in. 

 long, much thicker than the stem. Spike 1 in. long ; fl. rather 

 more whorled than as represented in E. B. S. Fr. unknown. 

 Deep water. Found floating loose in Lough Comb, Galway. 

 { Mr. Fryer refers this to P. lucens and Mr. Bennett to P. lucens X pra- 

 P. VIII. I. 



18. P. pralon'yus (Wulf.); I. pellucid oblong -lanceolate half- 

 clasping blunt and hooded at the end entire, slip, not winged, fr. 

 keeled on the back when fresh keeled or winged when dry, pe- 

 duncle very long equal, spikes many-flowered. E. B. S. 2858. 

 It. vii. 33. St. long, growing in deep water, L. with parallel 

 veins adjoining the midrib. Peduncles 6 12 in. long. Spikes 

 1 2 in." long. Ilivers and ditches, rare. P. V. VI. E. S. I. 



19. P. perfolidtus (L.) ; st. round, I. -pellucid cordate-ovate or 

 ovate-lanceolate clasping not hooded, fr. rounded on the back 

 when fresh keeled when dry, peduncle equal. E. B. 168. R. 

 vii. 29. St. long, slightly branched, rather dichotomous at the 

 top. Peduncles rather thick and short. Spikes short. [A state 

 with 1. elongate almost lanceolate has been referred to var. lanceolatus 

 (Blytt).] Lakes and streams. P. VII. E. S. tj 



20. P. crispus (L.) ; st. compressed, L pellucid linear-oblong 

 blunt sessile serrate wavy,//', with a long beak keeled on the 

 back when dry [base of keel with a long projecting tooth, A. Fryer], 

 peduncle equal. E. B. 1012. R. vii. 29 30. St. much 

 branched. Ped. long. Spikes few-flowered. Beak as long as 

 the nut. L. usually crisped at the edges, occasionally flat (P. 

 serratus L.). [P. Cooperi (Fryer) is P. crispus X perfoliatus arid P. 

 Bennettii (Fryer) is P. crispus X obtusifolms.~\ Bitches and streams. 

 P. VI. E. S. I. 



*** L. all submersed, alternate, linsar-liyulate ; stipules free. 



21. P. zosterifolius (Schum.) ; st. flattened, I. linear-acumi- 

 nate with 3 principal and many close parallel intermediate veins 

 occupying the whole surface, spikes cylindrical upon long ped.j 

 sep. transversely oval, fr. ubovate keeled, style terminal. 

 E. B. S. 2685. R. vii. 27. P. cuspidatus Sm., P. compressus- 

 Fries, Hook. Ped. 2 4 in. long. Spikes 10 15-flowered. 

 Inner edge of fr. rounded ; faces a little convex. L. suddenly 

 acuminate or apiculate. Rivers and lakes. P. VI. E. S. 



22. P. acutifolius (Link) ; st. flattened, /. linear-acuminate 

 with 3 principal and many close parallel intermediate veins occu- 

 pying the whole surface, spikes ovate about as long as the short 

 ped., sep. rhomboidal, fr. broadly j-obovate compressed inner 



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