POTAMOGETON 5x9 



4. Kennet. In a ditch adjoining the Thames near Caversham 



Bridge, Borrer, 1. c. 



5. Loddon. Near Aston Ferry and Hurley. Near Bray. 

 P.prae''ongiis is recorded for Bucks, Oxfordshire, and Surrey. 



P. perfoliatum, Linn. Sp. PI. 126 (1753). 



Top. Bot. 417. Syme, E. B. ix. 42, t. 1412. N3'man, 682. Fl. Oxf. 284. 



Native. Lacustral. Ponds, rivers, ditches, and canals. Common and 



widely distributed. P. July-August. 

 First record. Oxford, Sir J. E. Smith, in Herb. Linn. Soc. 1800. Loddon, 

 Mr. S. Budge, 1800, in Herb. Brit. Mus. The records iu Sibthorp's 

 Flora Oxon. of this and other plants of the Thames would necessarily 

 include Berkshire localities. 

 P. perfoliatum. is too frequent in all our larger streams and canals to 

 need an enumeration of localities. 



Between Eynsham and Sliilford, and in the Canal between Marcham 

 and Abingdon, a form with rounder leaves occurs. Hitherto I have 

 been unsuccessful in my search for a hybrid with P. crispum, which 

 we may expect to occur. 



P. perfoliatum occurs in all the bordering counties. 



P. crispum, Linn. Sp. PL 126 (1753^. Greater Watet- Caltrops. 



Top. Bot. 416. Syme, E. B. ix, 43, t. 1413. Nyman, 682. Fl. Oxf. 284. 



Native. Lacustral. Ponds, streams, and ditches. Bather common. 



P. June-July. 

 First recorded by Mr. H. Boswell in Britt. Contr. 1871, 



1. Isis. Near Bablock Hythe. Wytham. Slirivenham. Lechlade. 



Buscot. 



2. Ock. In the Thames, Boswell, 1866. Sandford, Ijaxcson in Oxf. 



Herb. Iffley. Kennington. Abingdon Canal, not unfrequent 

 between Abingdon and Marcham, Steventon, Wantage, &c. 

 Wittenham. Appleford. Radley, &c. 



3. Pang. Moulsford. Bradfield. Pangbourn. Tilehurst, &c. 



4. Kennet. Burghfield. Theale. Benham. Hungerford. 



5. Loddon. Loddon, Budge. Windsor, BoVoyi King. Wargrave. 



Near Shurlock Row. Shottesbrooke. Virginia Water. Spencer's 

 Wood Common. Winkfield. Arborfield. Near Windsor. Sand- 

 hurst, &c. 



Var. SERRATUM (Huds. Fl. Angl. 61 (1762), as a species). 



1, Isis. Shrivenham. Wytham. Near Botley. Near Eynsham. 

 2. Ock. Sandford. Kennington. Radley. 3. Pang. Mouls- 



ford. Langley Hall, in a pond. 4. Kennet. Padworth. 



Aldermaston. Burghfield. In Wigmoreash Pond at 912 feet 

 altitude. 5. Loddon. Sonning Meadows, Tufnail. Sandhurst. 

 Near Hurst. Near Binfield. 



