284 FLORA OF OXFORDSHIRE. 
Native. Lacustral. Rivers. Locally common. P. May. 
First record, W. Baster, about 1840, sub nom. lanceolatus. 
6. Thame. River Thame, ‘lanceolatus’ W. Bx. Oxford, Hb. Br. 
Mus. 1847. Sandford Lasher, W. T. Dyer, Hb. Br. Mus. and 
Journ. Bot. vol. ix. p. 148. Abundant in stream from the new 
boat house to Sandford, and at intervals southwards. 
7. Thames. Near Caversham Bridge, Supp. E. Bot. Moulsford. 
Berks. Canal at Marcham, Moulsford, Caversham. Northants, absent 
from Bucks, Gloster, or Warwick. 
P. perfoliatus, LD. 
Top. Bot. 417. Syme, E. B. ix. 42. 1412. Nym. 682. 
Native. Lacustral. Ponds, rivers, ditches, canal. Common. P. July. 
Occurs in all the districts. 
First record, Sib. 1794. 
A form with shorter leaves was noticed between Eynsham and Shilford. 
P. crispus, L. 
Top. Bot. 416. Syme, E. B. ix. 43. 1413. Nym. 682. 
Native. Ponds, streams, and ditches. Common. P. June, July. 
First record, Sib. 1794. 
3. Swere. Canal, Wroxton Pond, Guill. Banbury, Twyford, Hardwick, 
Adderbury, A. Fr. Clattercut Reservoir, abundant. 
4. Ray. Marston, Heyford, Islip. 
5, Isis. Christ Church Meadow, Sib. Eynsham, Oxford Canal. 
6. Thame. Cuttle Brook, Thame, Hd. Br. Menmarsh Farm, A. Fr. 
Sandford, Hb. Lawson. Iffley, ete. 
7. Thames. Caversham. 
Var. P. serratus, Huds. 
3. Swere. Crispus, a small state with less crisped leaves, Kilby’s 
Meadows, Bees. 
4. Ray. Plentiful in ditches about Marston. 
5. Isis. Near Botley, Eynsham. 
7. Thames. Whitchurch, see Rep. of Ree. Club, 1881. Woodeote, 
Hollindridge Farm, Saunders’ Green. 
Clusius’ figure in Johnson’s Ger. of crispus is annexed to a description 
of densus. 
P. densus, L. 
Top. Bot. 412. Syme, E. B. ix. 44.1414. Nym. 682. 
Native. Shallow streams. Not uncommon. P. June, July. 
First record, Sib. 1794. 
2. Ouse. Hethe. 
3. Swere. Broughton Jack Brook, Wroxton, Neithrop, Drayton, 
T. Bees. Somerton, Tadmarton. 
