520 NAIADACEAE 



This is by some botanists considered to be only a young state, but 

 I have seen it fruiting. For a most interesting account of this Pond- 

 weed, see a paper by that most accurate and painstaking observer of 

 this critical genus, Mr. A. Fryer, in Journ. Bot. (1890) 225. 



P. crisjmm occurs in all the bordering counties. 



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



Top. Bot. 412. Syme, E. B. ix. 44, t. 1414. Nyman, 682. Fl. Oxf. 284. 



Native. Lacustral. Shallow streams, ditches, ponds, &c. Locally 

 common. P. June -August. 



First record. Oxford, Sir J. E. Smith, in Herb. Brit. Mus. 1800. Pub- 

 lished as P. clensus in Russell's Cat. 1839. 



1. Isis. Near Lechlade. Near Wytham. Ashbury. 



2. Ock. Marcham, Walker. Ferry Hinksey, Dyer. Uffington. Fril- 



ford. Radley. Lockinge. Wantage. Near Abingdon. 



3. Pang. Pangbourn, Kewbould. Bradfield. Near Tilehurst. 



■1. Kennet. In the Lambourn near Ham Mills, Russell, I. c. Sliefford. 



Kintbury. Near Walbury Hill, in Wigmoreash Pond, 912 feet. 



Newbury. Benham. Hampstead Marshall. 

 5. Loddon. Sonning Meadows, Tufnail. Near Shurlock Row. Near 



Wargrave. In Virginia Water. Bisham. 

 Sometimes the plant is very dwarfed, and an acute-leaved form 

 also occurs. 



P. densum occurs in all the bordering counties. 



P. conipressum, Linn. Sp. PI. 127 (1753% and Fries, Koch, Nyman, 

 Willkomm et Lange, Gr. et Godr., &c., but not of Linn. Herb. 



P. zoster if olius, Schum. Enum. PI. Saell. i. 50 (1801). 



Top, Bot. 415. Syme, E. B. ix. 45, t. 1415. Nyinan, 683. Fl. Oxf. 285. 



Native. Lacustral. Rivers and canals. Locally common. P. June- 

 August. 



First record. P. compressum. Pondweed with a flat stalk grows 

 plentifully about . . . Reading, Caversham, . . . Milne and Gordon, 

 Indigenous Bot. 210, 1793. [Probably refers to this species.] P. 

 zoster if olius, Isis at Oxford, M. A. Lawson in Herb. Brit. Mus., Journ. 

 Bot. 16, 1871, and Herb. Brit. Mus. 1870. 



2. Ock. Isis at Oxford, Lawson, I. c. Nuneham, as P. graminewn, 



and Ferry Hink!?ey, Bosicell. Sandford, the author in Rej). of Exch. 

 Club, 1885. Sandford, Laioson. Ifiley, just below the Mill, 

 fruiting freely. Near the University Boat House. Abundant 

 in the Canal between Abingdon and Wantage, the author, Rep. 

 Bot. Exch. Club, 1892. 



3. Pang. Moulsford. Streatley. Near Tilehurst. 

 5. Loddon. Near Sonning. Bray. Near Windsor. 



P. compressum is recorded for Oxfordshire, Bucks, and Surrey. 



