NAIADACE^. 107 



Canal at Greenford. Stanmore. (Flor. Midd.) It 

 must not be confounded with the similar Anacharis Alsi- 

 nastrum, which chiefly differs by its having three leaves 

 in a whorl instead of two opposite ones. 



2. P. pectinatus. L. (Fennel-leaved Pondweed.) 

 Ponds and streams. 6, 7. 



Canal at Greenford ; Ruislip Reservoir. Canal at 

 Alperton. (Flor. Midd.) 



3. P. pusillus. L. (vSmall Linear-leaved Pondweed.) 

 Ditches and still waters. 6, 7. 



Abundant in the Canal at Greenford, pond by Headstone 

 Drive. 



4. P. compressus. L. 



Ditches and ponds. 7. 

 Harrow Weald. (Edition i.) 



5. P. crispus. L. (Curled-leaved Pondweed.) 

 Ditches and rivers. 6, 7. 



Kenton ; Grove Pond, Harrow ; Lake in Harrow Park, 

 most abundant ; Canal, Greenford ; and ponds at Roxeth ; 

 near Waxwell, Pinner. Stanmore. (Flor. Midd.) 



6. P. perfoliatus. L. (Perfoliate Pondweed.) 

 Ditches and lakes. 7. 



Canal at Greenford and Alperton. 



7. P. natans. L. (Sharp-fruited Broad-leaved Pond- 



weed.) 



Stagnant waters and slow streams. 6, 7. 

 Everywhere abundant. Harrow Weald. (Flor. Midd.) 

 Perivale. (Lees.) 



