462 CERATOPHYLLACEAE 



First record. P. nigra, about Oxford, Baxter, Phaen. Boi. n. 506, 1843. 



The trees at Ba block Hythe were figured in the Garden, 123, 

 February 14, 1885. 



* At the huge Sinodun hill a pretty belt of trees runs along the 

 water's edge, tall black poplars being the most conspicuous,' G. D. Leslie 

 in Our River. 



The Black Poplar is never an upright tree, but always slants 

 to a slight extent. 



P. nigra is found in all the bordering counties. 



CERATOPHYLLACEAE, A. Gray, Ann. Lye. New York, 



iv. 41 (1837). 



CERATOPHYLIiUM, Linn. Gen. n. 944. 



C. demersum, Linn. Sp. PL 992 (1753). Hoi-ned Pondweed. 



Top. Bot. 170. Syme, E. B. viii. 123, t. 1276. Nyman, 251, Fl. Oxf. 122. 



Native. Lacustral. Elvers, ditches, ponds. Not common, but 



scattered through the county. P. August-September. 

 First record. Wallingford, Mr. W. Willis in Baxter's Phaen. Bot. 260, 

 1837. 



1. Isis. Buckland, PosM;e?L Buscot, Near Wytham (d). 



2. Ock. About Wallingford, Willis, I. c. Marcham. Wantage. 



Abingdon (d). 



3. Pang. Near Moulsford, in the Thames, the author in Rep. of Rec. 



Club, 1880. 



4. Kennet. Theale (d). Southcote. Padworth. Aldermaston. 



Newbiuy. 



5. Loddon. Sonning, Tufnail. Ponds at foot of Winter Hill, Britt. 



Contr. Near Remenham. Park Place Lake, Stayiton. Winkfield. 



Sandhurst. Ruscombe. In the grounds of Frogmore. One 



growing specimen, which occurred in a stream near the 



Home Park at Windsor, was nearly enclosed by a species of 



fresh-water sponge. The Ceratophyllum appeared to be healthy 



despite its environment, which may have been of a symbiotic 



character. 



The foregoing records may be taken to represent the occurrence of 



the aggregate species since, from the plant so often failing to fruit, 



it has been impossible to say to which sub-species the specimens 



belong. 



I have appended a ' d ' to those records in which I have satisfied 

 myself that the restricted C. demersum is found. 



Aggregate C. demersum is found in all the bordering counties. 



In the Flora ofOxfordshire I referred to this species, '■Millefolium aquaticum 

 cornutum^ in the ditches about Oxford,' Merrett's Pinax ; being led to this 



