352 94. POTAMOGETONACE^E. 



** L. all submersed, membranous, lanceolate or broader; 

 stipules free. 



7. P. lucens (L.); I- pellucid oval or lanceolate stalked denti- 

 culate and apiculate, stip. winged, fr. obtuse on the back and 

 slightly keeled when fresh, peduncles swelling upwards, spikes 

 cylindrical densely flowered. E. B. 376. R. vii. 36. All the 

 stipules have two prominent wings on their back. Spikes long, 

 about equalling the peduncles. According to Mr. W. Wilson 

 " ovate-lanceolate moderately acute coriaceous 1." sometimes 

 occur. When the limb of the 1. is much reduced in size and the 

 midrib prominent and resembling a long spine, it is the P. acu- 

 minatus Schum. Common in deepish water. P. VI. 



8. P. longifolius (Gay?) ; I. 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, not 

 denticulate, nearly sessile with very short stalks. Stipules green, 

 lanceolate, with 2 narrow wings on the back. Fed. 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 E, B. S. Fr. unknown. 

 Deep water. Lough Corrib, Galway. Mr. J. Ball. P. VIII. I. 



9. P. pr&longus (Wulf.) ; I. pellucid elongate-oblong half- 

 clasping blunt and hooded at the end entire, stip. 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. 

 Peduncles 6 12 in. long. Sptkes 1 2 in. long. Rivers and 

 ditches, rare. P. VI. 



10. P. perfoliatus (L.); st. round, I. 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. 



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

 blunt sessile serrate wavy, fr. with a long beak keeled on the 

 back when dry, peduncles equal. E. B. 1012. E. vii. 2930. 

 St. much branched. Ped. long. Spikes few-flowered. Beak 

 as long as the nut. L. usually crisped at the edges, occasionally 

 flat (P. serratus Huds.). Ditches and streams. P. VI. 



*** L. all submersed, alternate, linear; stipules free. 



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

 nate with 3 principal and many close parallel intermediate 



